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6: Mikrobiese Fisiologie - Biologie

6: Mikrobiese Fisiologie - Biologie



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6: Mikrobiese Fisiologie

Mikrobiese Biotegnologie | Biotegnologie

Die onderstaande artikel verskaf 'n nota oor mikrobiese biotegnologie.

Biotegnologie is die toepassing van lewende organismes en hul produkte in industriële prosesse op groot skaal. Mikrobiese biotegnologie is daardie aspek van biotegnologie wat die gebruik van mikroörganismes of hul produkte behels.

Mikrobiese biotegnologie word soms ook na verwys as industriële mikrobiologie wat 'n ou veld is wat nuwe dimensies gekry het as gevolg van die ontdekkings wat gemaak is in die veld van genetiese ingenieurswese in vitro manipulasie van DNA-molekules om nuwe kombinasies van gene of rye te genereer, om die geen onder die beheer van verskillende regulatoriese sisteme, om 'n spesifieke mutasie in 'n molekule in te voer, ens.

Industriële mikrobiologie het aanvanklik ontstaan ​​deur die vestiging van alkoholiese fermentasieprosesse om wyn en bier te produseer. Daarna het die mikrobiese produksie van antibiotika en voedseladditiewe soos aminosure, ensieme, butanol en sitroensuur ontstaan.

Genetiese ingenieurswese het ons in staat gestel om mikroörganismes te gebruik vir die produksie van nuwe stowwe wat die mikroörganismes nie normaalweg kon vervaardig nie, soos die produksie van hormoon insulien 'n pankreashormoon wat die vervoer van glukose na selle stimuleer. Die produksie van insulien deur bakterieë was moontlik as gevolg van genetiese ingenieurstegnieke om menslike insuliengeen in 'n bakterie in te voeg.

Mikrobiese biotegnologie kan onder twee subopskrifte verdeel word:

(1) Tradisionele mikrobiese tegnologie wat die grootskaalse vervaardiging is van produkte wat normaalweg deur mikroörganismes geproduseer word.

(2) Mikrobiese tegnologie met geneties gemanipuleerde mikroörganismes waarin nuwe gene ingevoeg is.

Industriële mikroörganismes:

Industriële mikroörganismes is daardie mikroörganismes wat noukeurig geselekteer is om een ​​of meer spesifieke produkte te maak. Industriële mikroörganismes word geselekteer vir hul metaboliese aktiwiteite wat in staat is tot spesifieke produkte en 'n hoë opbrengs van bepaalde metaboliete lewer.

Om die verlangde doelwitte van hoë metaboliese spesialisasie te bereik, word die industriële stamme geneties gemodifiseer deur mutasie of rekombinasie deur tegnieke van genetiese ingenieurswese te gebruik. Die geringe metaboliese weë word óf verlaag óf uitgeskakel. Alhoewel die industriële stamme goed kan groei onder hoogs gespesialiseerde kunsmatige toestande van die fermenteerder, kan hulle swak groei-eienskappe toon in natuurlike toestande van mededingende omgewings.

Bron van industriële stamme:

Die aanvanklike en uiteindelike bron van industriële stamme was ongetwyfeld die natuur, maar deur die ervaring van jare se grootskaalse mikrobiese prosesse is perfeksie bereik vir groter opbrengs. Die stamme wat so ontwikkel is, is in kultuurversamelings gedeponeer. Om 'n nuwe industriële proses gepatenteer te kry, moet die aansoeker 'n stam wat in staat is om die proses voort te sit, in 'n erkende kultuurversameling deponeer.

Alhoewel die meeste industriële maatskappye huiwerig sou wees om hul beste kulture by enige erkende kultuurversameling te deponeer, dien hierdie versamelings tog as 'n gereed bron van kulture: 'n Baie groot lys van kultuurversamelings word in die “World Directory of Collection of Microorganisms” gegee. (1982), bygewerk deur VF Mc Gowan en V.B.D. Skerman.

Sommige van die algemene kultuurversamelings met hul afkorting, volle naam en liggings word hieronder gegee:

AMRC (FAO-WHO International Reference Center for Animal Mycoplasma) Instituut vir Mediese Mikrobiologie, Universiteit van Aarhas, Denemarke.

ATCC (American Type Culture Collection) 12301.

Parklawan Drive, Rockvilla, Maryland 20852, VSA.

CBS (Central Bureau Voor Schimmelcultures) Ousterstraat 1, Baarn, Nederland.

CCEB (Culture Collection of Entomophagous Bacteria) Institute of Entomology, Tsjeggiese Akademie vir Wetenskappe, Femingovo N2, Praag 6, Tsjeggo -Slowakye.

CDDA (Kanadese Departement van Landbou) Ottawa, Kanada.

CIP (Collection of Institute Pasteur) Rue due Dr Roux, Paris 15, and France.

CMI (Commonwealth Mycological Institute, tans bekend as International Mycological Institute), Kew, Verenigde Koninkryk.

DSM (Deutsche Samn — dung von Microorganismen) Grisebachstrasse 8, Gottingen, Bondsrepubliek Duitsland.

FAT (Fakulteit Landbou, Tokio Universiteit) Tokio, Japan.

IAM (Institute of Applied Microbiology) Universiteit van Tokio, Bunkyo-ku, Tokio, Japan.

IFO (Instituut van Fermentasie) 4-54 Jusonishinocho, Osaka, Japan.

IMI (International Mycological Institute) Bakeham Lane, Egham, Surrey TW 209 TY, Verenigde Koninkryk.

IMY (Instituut vir Mikrobiologie en Virologie) Akademie vir Wetenskappe van die Ukranian S.S.R., Kiev.

NCIB (National Collection of Industrial Bacteria) Aberdeen, Skotland.

NCTC (National Collection of Type Cultures), Londen, VK.

NRRL (Northern Regional Research Laboratory) Peoria, IL VSA.

UQM (Kultuurversameling, Departement Mikrobiologie, Universiteit van Queensland), Herston, Brisbane 4006, Australië.

UWO (Universiteit van Wes-Ontario Kultuurversameling, Departement Plantwetenskappe), Ontario N6A 587, Kanada.

Instandhouding en bewaring van kulture is ook baie noodsaaklik om kulture uit die kultuurversamelings te kry.

Mikro-organismes van oorspronklike bronne word hoogs gemodifiseer in die laboratorium. Die wysiging word gedoen om 'n teiken van hoër opbrengs te bereik. Een van die interessante voorbeelde van die progressiewe verbetering is die antibiotika penisillien wat deur die swam Penicillium chrysogenum geproduseer word. Die produksie van penisillien op industriële skaal was vir die eerste keer 1 tot 10 pg/ml.

Die programme vir stamontwikkeling, vergesel van veranderinge in medium en die groeitoestande na harde werk van baie jare, het egter die opbrengs van antibiotika penisillien tot ongeveer 50 000 pg/ml verhoog. Dus, byna 50 000 keer toename was moontlik deur mutasie en seleksie sonder om genetiese ingenieurstegnieke te betrek. Die toevoeging van nuwe genetiese ingenieurstegnieke het die kanse vir nog groter opbrengs verhelder.

Vereistes vir 'n Industriële Mikro-organisme:

Nie almal nie, maar slegs 'n paar geselekteerde mikroörganismes is geskik vir toepassing in industriële produksie. 'n Industriële mikro-organisme moet geredelik groei in grootskaalse vervaardigingstoerusting. Ongetwyfeld 'n industriële mikro-organisme’ se eerste vereiste is om die produk van belang te vervaardig, maar dit moet ook vinnig groei en op relatief goedkoop kultuur media.

'n Industriële mikro-organisme behoort die moontlikheid te hê om geneties manipulasies te ondergaan vir sy stamverbetering. 'N Industriële mikro -organisme behoort nie patogeen te wees nie en moet ook geen giftige produkte produseer wat skadelik vir mense, diere of plante kan wees nie.


Omvang

Mikrobiese Fisiologie en Metabolisme publiseer artikels oor die onderwerpe van mikrobiese struktuur, metabolisme en fisiologie.

Genoomvolgordebepaling, vergelykende genomika en sisteembiologie het 'n ongekende stimulus aan molekulêre mikrobiologiese navorsing verskaf, terwyl dit globale insigte verskaf het in die repertorium van biochemiese reaksies wat individuele mikrobes definieer. Oor die verloop van 'n paar dae is dit nou moontlik om globale insigte te verkry in die metaboliese prosesse wat beskryf hoe mikroörganismes die energie vir hul groei verkry, die boustene vir biosintese produseer, daardie materiale in sellulêre bestanddele polimeriseer en dit in lewendes saamstel. selle en inligting wat voorheen 'n leeftyd (of meer) geneem het om te ontdek en te beskryf. Insigte word toenemend verkry uit kultuur-onafhanklike of multi-organisme-eksperimente, wat mikrobioloë bevry het van byna 150 jaar van fiksasie op suiwer-kultuur studies &ndash dikwels uitgevoer onder toestande wat min te doen het met dié wat deur natuurlike bevolkings ervaar word. Namate ons geïntegreerde kennis van mikrobiese fisiologie op hierdie nuwe en opwindende maniere vorder, neem geleenthede vir metaboliese ingenieurswese van mikroörganismes en selfs mikrobes de novo & ndash om produkte wat nuttig is vir die mensdom, ook vinnig vooruit. Mikrobiese Fisiologie en Metabolisme streef daarna om die voorpuntnavorsing aan te bied wat die onderbou verskaf van ons kennis van hoe bakteriese en argeale struktuur tot funksionering lei, hoe metaboliese prosesse gereguleer word, hoe mikrobes op omgewingstressors reageer, en hoe mikrobes gemanipuleer kan word om te verbeter hul groei of die produksie van gewenste produkte. Die afdeling sal artikels publiseer wat nuwe metodes, metaboliete, reguleerders, regulatoriese reaksies en meganismes beskryf, en globale ontledings gebaseer op genomiese, metagenomiese en stelselbiologiese metodes, sowel as studies wat afkomstig is van klassieke fisiologiese en metaboliese benaderings. Ons sal ook fisiologiese en metaboliese navorsing oor eukariotiese mikrobes oorweeg, alhoewel outeurs susterafdelings, soos swamfisiologie en metabolisme, meer geskikte plekke vir sulke studies kan vind.

'N Belangrike doel van mikrobiese fisiologie en metabolisme is om wetenskaplikes te help om hul navorsingsresultate vinnig aan ander wetenskaplikes te kommunikeer deur middel van 'n oop, gratis toegangsplatform, vry van sommige beperkings (bv. Beperkte gebruik van kleurfigure) wat inherent is aan tydskrifte wat afhanklik is van druk formaat. 'N Bykomende doelwit is om 'n forum te bied waarin wetenskaplikes hul belangrikste resultate aan die publiek kan kommunikeer op 'n manier wat sekondêre onderwys en algemene bewustheid van die publiek kan versterk oor die kritieke rolle wat mikroörganismes speel in globale prosesse wat ons brose, veranderende omgewing definieer en in stand hou. .


Pad deur die Mikrobiologie Phd-program

Voor die begin van die herfssemester bespreek nuwe studente hul agtergrond en belangstellings met die gegradueerde adviseurs, wat help met die beplanning van akademiese programme. Gedurende die eerste semester skryf alle nuwe studente in vir 'n tweekrediet-seminaar waarin fakulteitslede hul huidige navorsingsprogramme opsom. Elke student roteer ook deur drie navorsingslaboratoriums vir tien weke elk in die eerste akademiese jaar. Die rotasies gee studente die geleentheid om areas van belangstelling te verken as moontlikhede vir Ph.D. navorsing.

In die eerste jaar moet studente inskryf vir die twee-semester kernkursus, PMB 220A-F. Die kernkursus bestaan ​​uit 6 modules wat die volgende onderwerpe dek: mikrobiese genetika, genomika en berekeningsbiologie, mikrobiese diversiteit en evolusie, selstruktuur en funksie, mikrobiese fisiologie en mikrobiese ekologie. Die Kwalifiserende Eksamen toets hierdie kennisvelde naby die einde van die student se tweede jaar. Benewens die kernkursus word PMB 202 en PMB 210 vereis. PMB 202 "Fakulteitsnavorsingsoorsig" stel studente bloot aan die navorsing van lede van die nagraadse groep, deur middel van kapsule -aanbiedings van hul voortgesette navorsing en die betekenis daarvan op die gebied van mikrobiologie. Die doelwitte van PMB 210 “Scientific Reasoning and Logic” is om studente te leer om wetenskaplike artikels krities te lees en te interpreteer.

Gedurende die eerste twee jaar moet alle studente inskryf vir twee seminaarkursusse op nagraadse vlak. Seminare bied aan studente die geleentheid vir mondelinge aanbieding van onderwerpe van besondere belang. Seminare laat studente ook individuele fakulteits- en ander studente in 'n kleingroep-omgewing ontmoet. Die Werkswinkel oor Onderrig, PMB 300, moet ook die herfssemester van 'n student se tweede jaar geneem word.

Nagraadse Student Onderrig (GSI)

Elke student dien as 'n Nagraadse Studente-instrukteur (GSI) vir ongeveer 20 uur per week vir twee semesters. Studente neem deel aan die GSI-opleidingskonferensie wat deur die Nagraadse Afdeling en die Nagraadse Vergadering geborg word en skryf in vir 'n tweekrediet-onderrigwerkswinkel. Studente word aangestel as 'n GSI vir 'n laer-afdeling kursus voordat hulle 'n GSI vir 'n hoër-afdeling kursus geborg deur die departement. Internasionale studente wat opgelei is in skole waar Engels nie die onderrigtaal is nie, moet die toets van gesproke Engels (TSE) slaag voordat hulle as onderwysassistente dien.

Lab Rotasies

Inkomende studente moet gedurende die eerste jaar deur drie verskillende laboratoriums roteer, ongeveer 10 weke per rotasie. Die student kan laboratoriums kies wat by die Nagraadse Groep geaffilieer is, of 'n laboratorium buite die Groep kies om 'n bepaalde vaardigheid aan te leer. Studente ondersoek geleenthede vir rotasies saam met die betrokke fakulteit en die gegradueerde adviseur. Die rotasies gee studente die geleentheid om 'n navorsingsgebied te ondersoek waarin hulle belangstel, maar geen direkte ervaring het nie.

In die meeste gevalle sal die rotasies laboratoriumwerk behels. Soms kan 'n rotasie egter die vorm van lees en bespreking aanneem. Alhoewel sommige inkomende studente belangstel in die spesifieke fakulteit vir proefskrifnavorsing, het studente rotasies nodig om blootstelling aan navorsing buite hul onmiddellike belangstellingsgebied te kry. Studente het die vryheid om verskillende geleenthede vir 'n geskikte hoofadviseur te ondersoek. Terwyl studente te eniger tyd belangstelling in enige spesifieke laboratorium kan toon, mag hulle nie vaste verbintenisse aangaan voordat hulle al drie rotasies voltooi het nie. Die student kies gewoonlik 'n navorsingsadviseur na die derde rotasie. In uitsonderlike gevalle kan die student 'n vierde laboratoriumrotasie neem. Nadat die keuse van 'n navorsingsadviseur geformaliseer is, begin die student 'n navorsingsprojek in die adviseur se laboratorium.

Kwalifiserende Eksamen

[prentbyskrif]

Israel Figueroa van die Coates Lab. Foto deur D. Galvez.

Die Kwalifiserende Eksamen assesseer die kandidaat se breë kennis van mikrobiese biologie en bepaal in-diepte kennis in die voorgestelde navorsingsarea. Die eksamen bestaan ​​uit 'n dialoog tussen die student en die eksaminatore om 'n forum te bied vir die student om die vermoë te demonstreer om te integreer en te ekstrapoleer uit inligting wat in die klaskamer en laboratorium verkry is. Die eksamen bied 'n manier om die student se voorbereiding en potensiaal vir 'n navorsings- of onderwysloopbaan op professorale vlak te evalueer. Dit beklemtoon die breedte, diepte en gesofistikeerdheid van kennis. Tydens die eksamen sal die student demonstreer:

  • Bemeestering van 'n beduidende hoeveelheid relevante kennis
  • Die vermoë om krities te dink en te skryf
  • Die vermoë om inligting wat in die klaskamer en laboratorium geleer is, toe te pas op die oplossing van relevante biologiese probleme

Die student neem gewoonlik die Kwalifiserende Eksamen normaalweg in die derde of vierde semester af. Die student sal, in oorleg met die Hoof Nagraadse Adviseur, 'n Eksamenkomitee van vier lede aanbeveel, goedgekeur deur die Nagraadse Afdeling. Hierdie komitee het ten minste drie gewone fakulteite uit die nagraadse groep en bevat verteenwoordigers van ten minste twee departemente. Adjunkprofessore kan as lede van die Komitee dien. Nie-senaatlede en fakulteite van ander kampusse kan dien na goedkeuring van die gegradueerde adviseur en dekaan van die nagraadse afdeling.

Nie later nie as een week voor die Eksamen sal die kandidaat twee navorsingsvoorstelle voorberei en aan die Komitee lewer, beide van die omvang en kaliber wat geskik is vir doktorale proefskrifnavorsing. Die student ontwikkel die onderwerpe van beide die hoof- en minderjarige voorstelle in oorleg met die Eksamenkomiteevoorsitter. Om vraagstelling in die kandidaat se voorgestelde navorsingsarea te fokus, moet die hoofvoorstel, in ongeveer drie bladsye, die spesifieke onderwerp wat vir tesisnavorsing voorgestel word, aanspreek. Om 'n uitgangspunt te bied vir bevraagtekening oor die omvang van mikrobiese biologie, behoort die klein voorstel, op ongeveer twee bladsye, 'n spesifieke onderwerp aan te spreek op 'n gebied wat aansienlik verskil van die benadering van die kandidaat se voorgestelde proefskrifnavorsing. Die voorstelle dien as basis vir die mondelinge eksamen, beperk dit nie.

Die student moet in oorleg met die Navorsingsadviseur en Nagraadse Adviseurs verseker dat die samestelling van die Eksamenkomitee hom toelaat om kennis te assesseer in beide areas wat deur die voorstelle gedek word. Enige eksaminator mag vrae in enige vakgebied vra. Ons beveel dus sterk aan dat die student met elke Komiteelid voor die Eksamen vergader. Die professor en student kan kies om op onderwerpe binne 'n bepaalde vakgebied te fokus en kan gereeld vergader om hierdie onderwerpe te bespreek. Solank as wat die Komitee die student se breë kennis van mikrobiese biologie voldoende assesseer, kan die Komitee addisionele areas bespreek deur onderlinge ooreenkoms tussen die student en die eksaminatore.

Die mondelinge eksamen sal ongeveer 3 uur duur. Ongeveer een derde van die eksamen dek die hoofvoorstel, met die oorblywende tyd wat aan die minderjarige voorstel en die breedte van mikrobiologie toegeken word. Om die kwalifiserende eksamen te slaag, vereis 'n eenparige stem van die Komitee.

Na afloop van die eksamen skryf die voorsitter van die komitee 'n kort verklaring oor die prestasie van die student op elke gebied. Hierdie opsomming, bygevoeg tot die student se lêer, dokumenteer dat die Komitee voldoende tyd aan Eksamenareas bestee het en rig ook die student se toekomstige program.

Gegradueerde Review

[prentbyskrif]

Beeld met vergunning van die Traxler Lab.

Evaluering van eerstejaarstudente se vordering vind aan die einde van die eerste jaar plaas. Die fakulteit vergader as 'n groep om eerstejaarstudente se grade en kernkursuskommentaar van instrukteurs, laboratoriumrotasie-evaluasies van fakulteitslede en enige studentekommentaar wat die student wil aanbied, te hersien. Die fakulteit bespreek elke student individueel en sy/haar vordering in die loop van die jaar, wat daartoe lei dat die student 'n hersieningsbrief ontvang wat deel uitmaak van die student se lêer. Die hersieningsbrief gee 'n opsomming van die student se vordering en kan spesifieke aanbevelings of kursusvereistes van die fakulteit insluit. Resensies oorweeg:

  • Bemeestering van 'n beduidende hoeveelheid relevante kennis
  • Die vermoë om krities te dink en te skryf
  • Die vermoë om inligting wat in die klaskamer en laboratorium geleer is toe te pas op die oplossing van relevante biologiese probleme

Verhandeling

Die student nooi 'n komitee van drie lede om as die Verhandelingskomitee te dien. (Die student kan 'n komitee van vier lede aanvra, of die Nagraadse Afdeling mag een in sekere omstandighede vereis). Die student identifiseer die Komiteelede in oorleg met die Hoof Nagraadse Adviseur. Die Komitee moet verteenwoordigers van ten minste twee akademiese departemente insluit. Die Voorsitter van die Komitee sal die Navorsingsadviseur wees, wat fakulteitslidmaatskap in die Nagraadse Groep moet hê. 'n Adjunk-fakulteitslid kan egter as Mede-Voorsitter saam met 'n gewone fakulteits Mede-Voorsitter dien. Die komitee moet ten minste een Akademiese Senaatslid hê.

Ten minste een keer per jaar sal hierdie Komitee met die student vergader en vordering evalueer. Die Nagraadse Afdeling vereis dat 'n vorm aan die Nagraadse Afdeling gestuur word wat die vordering van die student sertifiseer. Lede van die Verhandelingskomitee sal ook die student adviseer oor die uitvoering van navorsing.

Alle lede van die Komitee moet die proefskrif goedkeur en onderteken voor die Ph.D. graad toegeken word.

Vir die Ph.D. graad, moet studente 'n verhandeling voltooi wat gebaseer is op oorspronklike en onafhanklike navorsing.

'n Eindeksamen word nie vereis nie. Alle studente moet egter 'n afrondingseminaar aanbied om die resultate van hul proefskrifprojek op te som en op vrae van die gehoor te reageer. Indien die fakulteit nie die seminaar bevredigend vind nie, kan hulle die student vra om die seminaar weer aan te bied om die bekommernisse aan te spreek.


Joernaal lys spyskaart

Departement Ekologie, Evolusie en Mariene Biologie, Universiteit van Kalifornië Santa Barbara, Santa Barbara, Kalifornië 93106 VSA

Departement Grondkunde, Universiteit van Wisconsin, Madison, Wisconsin 53706, VSA

Natuurlike Hulpbronne Ekologie Laboratorium, Colorado State University, Fort Collins, Colorado 80523-1499 VSA

Departement Ekologie, Evolusie en Mariene Biologie, Universiteit van Kalifornië Santa Barbara, Santa Barbara, Kalifornië 93106 VSA

Departement Grondkunde, Universiteit van Wisconsin, Madison, Wisconsin 53706 VSA

Natural Resources Ecology Laboratory, Colorado State University, Fort Collins, Colorado 80523-1499 VSA

Abstrak

Mikroörganismes het 'n verskeidenheid evolusionêre aanpassings en fisiologiese akklimatiseringsmeganismes wat hulle in staat stel om te oorleef en aktief te bly in die lig van omgewingsstres. Fisiologiese reaksies op stres het koste op organisatoriese vlak wat kan lei tot 'n veranderde ekosisteemvlak C, energie en voedingsvloei. Hierdie grootskaalse impakte spruit uit direkte effekte op aktiewe mikrobes se fisiologie en deur die samestelling van die aktiewe mikrobiese gemeenskap te beheer. Ons kyk eers na 'n paar algemene aspekte van hoe mikrobes omgewingstres ervaar en hoe hulle daarop reageer. Ons bespreek dan die impak van twee belangrike ekosisteemvlak stressors, droogte en bevriesing, op mikrobiese fisiologie en gemeenskapsamestelling. Selfs as die reaksie van die mikrobiese gemeenskap op stres beperk is, is die fisiologiese koste van grondmikrobes groot genoeg om groot verskuiwings in die toewysing en lot van C en N. te veroorsaak, byvoorbeeld, sodat mikrobes die osmoliete kan sintetiseer wat hulle nodig het om enkele droogte-episode kan hulle tot 5% van die totale jaarlikse netto primêre produksie in grasveld-ekosisteme verbruik, terwyl akklimatisering aan vriestoestande Arktiese toendragronde verander van immobilisering van N gedurende die groeiseisoen na mineralisering gedurende die winter. Ons stel voor dat die meer effektiewe integrasie van mikrobiese ekologie in ekosisteem-ekologie 'n meer volledige integrasie van mikrobiese fisiologiese ekologie, bevolkingsbiologie en proses-ekologie sal vereis.


Inhoud

Diere wysig

Mense wysig

Menslike fisiologie poog om die meganismes te verstaan ​​wat werk om die menslike liggaam aan die lewe en funksionering te hou, [4] deur middel van wetenskaplike ondersoek na die aard van meganiese, fisiese en biochemiese funksies van mense, hul organe en die selle waaruit hulle saamgestel is. Die hoofvlak van fokus van fisiologie is op die vlak van organe en sisteme binne sisteme. Die endokriene en senuweestelsels speel groot rolle in die ontvangs en oordrag van seine wat funksie in diere integreer. Homeostase is 'n belangrike aspek met betrekking tot sulke interaksies binne plante sowel as diere. Die biologiese basis van die studie van fisiologie, integrasie verwys na die oorvleueling van baie funksies van die stelsels van die menslike liggaam, sowel as die gepaardgaande vorm daarvan. Dit word bereik deur kommunikasie wat op 'n verskeidenheid maniere plaasvind, beide elektries en chemies. [6]

Veranderinge in fisiologie kan die geestelike funksies van individue beïnvloed. Voorbeelde hiervan is die uitwerking van sekere medikasie of toksiese vlakke van stowwe. [7] Gedragsverandering as gevolg van hierdie stowwe word dikwels gebruik om die gesondheid van individue te bepaal. [8] [9]

Baie van die grondslag van kennis in menslike fisiologie is deur diere-eksperimentering verskaf. As gevolg van die gereelde verband tussen vorm en funksie, is fisiologie en anatomie intrinsiek gekoppel en word dit in tandem bestudeer as deel van 'n mediese kurrikulum. [10]

Plante wysig

Plantfisiologie is 'n subdissipline van plantkunde gemoeid met die funksionering van plante. Naverwante velde sluit in plantmorfologie, plantekologie, fitochemie, selbiologie, genetika, biofisika en molekulêre biologie. Fundamentele prosesse van plantfisiologie sluit in fotosintese, asemhaling, plantvoeding, tropismes, nastiese bewegings, fotoperiodisme, fotomorfogenese, sirkadiese ritmes, saadontkieming, dormansie en huidmondjiesfunksie en transpirasie. Absorpsie van water deur wortels, produksie van voedsel in die blare, en groei van lote na lig is voorbeelde van plantfisiologie. [11]

Selle wysig

Alhoewel daar verskille is tussen diere-, plant- en mikrobiese selle, kan die basiese fisiologiese funksies van selle verdeel word in die prosesse van seldeling, seldeling, selgroei en selmetabolisme.

Vergelykende fisiologie Edit

Met betrekking tot evolusionêre fisiologie en omgewingsfisiologie, oorweeg vergelykende fisiologie die diversiteit van funksionele eienskappe oor organismes heen. [12]

Die klassieke era Edit

Die studie van menslike fisiologie as 'n mediese veld het sy oorsprong in die klassieke Griekeland, in die tyd van Hippokrates (laat 5de eeu v.C.). [13] Buite die Westerse tradisie kan vroeë vorme van fisiologie of anatomie gerekonstrueer word dat dit omtrent dieselfde tyd in China, [14] Indië [15] en elders teenwoordig was. Hippokrates het sy oortuigingsisteem, die teorie van humors, geïnkorporeer, wat uit vier basiese stowwe bestaan ​​het: aarde, water, lug en vuur. Elke stof is bekend vir die ooreenstemmende humor: onderskeidelik swart gal, slym, bloed en geel gal. Hippokrates het ook 'n paar emosionele verbande opgemerk met die vier humorsinne, waarop Claudius Galenus later sou uitbrei. Die kritiese denke van Aristoteles en sy klem op die verhouding tussen struktuur en funksie was die begin van die fisiologie in Antieke Griekeland. Net soos Hippokrates, het Aristoteles oorgegaan tot die humoristiese teorie van siekte, wat ook uit vier primêre eienskappe in die lewe bestaan: warm, koud, nat en droog. [16] Claudius Galenus (ongeveer 130-200 nC), bekend as Galen van Pergamum, was die eerste om eksperimente te gebruik om die funksies van die liggaam te ondersoek. Anders as Hippokrates, het Galen aangevoer dat humorale wanbalanse in spesifieke organe, insluitend die hele liggaam, geleë kan wees. [17] Sy wysiging van hierdie teorie het dokters beter toegerus om meer presiese diagnoses te maak. Galen het ook afgespeel van Hippokrates se idee dat emosies ook aan die humor gekoppel is, en die idee van temperamente bygevoeg: sanguine stem ooreen met bloed flegmaties is gekoppel aan slym geel gal is verbind met choleriese en swart gal stem ooreen met melancholie. Galen het ook gesien hoe die menslike liggaam bestaan ​​uit drie verbind stelsels: die brein en senuwees, wat verantwoordelik is vir die gedagtes en gewaarwordinge van die hart en are, wat lewe en die lewer en are gee, wat toegeskryf kan word aan voeding en groei. [17] Galen was ook die stigter van eksperimentele fisiologie. [18] En vir die volgende 1 400 jaar was Galeniese fisiologie 'n kragtige en invloedryke hulpmiddel in medisyne. [17]

Vroeë moderne tydperk Edit

Jean Fernel (1497–1558), 'n Franse geneesheer, het die term "fisiologie" bekendgestel. [19] Galen, Ibn al-Nafis, Michael Servetus, Realdo Colombo, Amato Lusitano en William Harvey word beskou as belangrike ontdekkings in die sirkulasie van die bloed. [20] Santorio Santorio in 1610's was die eerste om 'n toestel te gebruik om die polsslag te meet (die pulsilogium), en 'n termoskoop om temperatuur te meet. [21]

In 1791 beskryf Luigi Galvani die rol van elektrisiteit in senuwees van ontleedde paddas. In 1811 het César Julien Jean Legallois respirasie in dieredisseksie en letsels bestudeer en die middelpunt van asemhaling in die medulla oblongata gevind. In dieselfde jaar het Charles Bell werk voltooi aan wat later bekend sou word as die Bell-Magendie-wet, wat funksionele verskille tussen dorsale en ventrale wortels van die rugmurg vergelyk het. In 1824 het François Magendie die sensoriese wortels beskryf en die eerste bewys gelewer van die serebellum se rol in ekwilibrasie om die Bell-Magendie-wet te voltooi.

In die 1820's het die Franse fisioloog Henri Milne-Edwards die idee van fisiologiese verdeling van arbeid bekendgestel, wat toegelaat het om "lewende dinge te vergelyk en te bestudeer asof hulle masjiene is wat deur die industrie van die mens geskep is." Geïnspireer in die werk van Adam Smith, het Milne-Edwards geskryf dat die "liggaam van alle lewende wesens, hetsy dier of plant, soos 'n fabriek lyk. Waar die organe, vergelykbaar met werkers, onophoudelik werk aan die verskynsels wat die lewe van die individu." In meer gedifferensieerde organismes kan die funksionele arbeid tussen verskillende instrumente of sisteme verdeel word (deur hom genoem as klere). [22]

In 1858 het Joseph Lister die oorsaak van bloedstolling en ontsteking bestudeer wat na vorige beserings en chirurgiese wonde ontstaan ​​het. Hy het later antiseptika in die operasiesaal ontdek en geïmplementeer, en gevolglik het die sterftesyfer weens chirurgie met 'n aansienlike hoeveelheid verlaag. [23]

Die Fisiologiese Vereniging is in 1876 in Londen gestig as 'n eetklub. [24] Die American Physiological Society (APS) is 'n nie-winsgewende organisasie wat in 1887 gestig is. Die Genootskap is "toegewy aan die bevordering van onderwys, wetenskaplike navorsing en verspreiding van inligting in die fisiologiese wetenskappe." [25]

In 1891 het Ivan Pavlov navorsing gedoen oor "voorwaardelike reaksies" wat honde se speekselproduksie in reaksie op 'n klokkie en visuele stimuli behels het. [23]

In die 19de eeu het fisiologiese kennis vinnig begin ophoop, veral met die verskyning van die Sel-teorie van Matthias Schleiden en Theodor Schwann in 1838. [26] Dit het radikaal gestel dat organismes bestaan ​​uit eenhede wat selle genoem word. Claude Bernard (1813–1878) se verdere ontdekkings het uiteindelik gelei tot sy konsep van milieu interieur (interne omgewing), [27] [28], wat later deur die Amerikaanse fisioloog Walter B. Cannon in 1929 as 'homeostase' aangeneem en as 'homeostase' voorgestel sou word. Met homeostase bedoel Cannon 'die handhawing van bestendige toestande in die liggaam en die fisiologiese prosesse waardeur dit gereguleer word. " [29] Met ander woorde, die liggaam se vermoë om sy interne omgewing te reguleer. William Beaumont was die eerste Amerikaner wat die praktiese toepassing van fisiologie gebruik het.

Negentiende-eeuse fisioloë soos Michael Foster, Max Verworn en Alfred Binet, gebaseer op Haeckel se idees, het uitgebrei wat bekend geword het as "algemene fisiologie", 'n verenigde wetenskap van lewe gebaseer op die selaksies, [22] later herdoop in die 20ste eeu as selbiologie. [30]

Laatmoderne tydperk Edit

In die 20ste eeu het bioloë begin belangstel in hoe ander organismes as mense funksioneer, wat uiteindelik die velde van vergelykende fisiologie en ekofisiologie voortgebring het. [31] Belangrike figure in hierdie velde sluit in Knut Schmidt-Nielsen en George Bartholomew. Mees onlangs het evolusionêre fisiologie 'n duidelike subdissipline geword. [32]

In 1920 het August Krogh die Nobelprys gewen omdat hy ontdek het hoe bloedvloei in kapillêre gereguleer word. [23]

In 1954 het Andrew Huxley en Hugh Huxley saam met hul navorsingspan die glyfilamente in skeletspier ontdek, vandag bekend as die glyfilamentteorie. [23]

Onlangs was daar intense debatte oor die lewenskragtigheid van fisiologie as 'n dissipline (Is dit dood of lewend?). [33] [34] As fisiologie deesdae miskien minder sigbaar is as tydens die goue eeu van die 19de eeu, [35] is dit grootliks omdat die veld geboorte gegee het aan sommige van die aktiefste gebiede van die huidige biologiese wetenskappe, soos as neurowetenskap, endokrinologie en immunologie. [36] Verder word fisiologie steeds dikwels gesien as 'n integrerende dissipline, wat data wat uit verskeie verskillende domeine kom, saamgevoeg kan word tot 'n samehangende raamwerk. [34] [37] [38]

Vroue in fisiologie Redigeer

Aanvanklik was vroue grootliks uitgesluit van amptelike betrokkenheid by enige fisiologiese samelewing. Die American Physiological Society, byvoorbeeld, is in 1887 gestig en het slegs mans in sy geledere ingesluit. [39] In 1902, the American Physiological Society elected Ida Hyde as the first female member of the society. [40] Hyde, a representative of the American Association of University Women and a global advocate for gender equality in education, [41] attempted to promote gender equality in every aspect of science and medicine.

Soon thereafter, in 1913, J.S. Haldane proposed that women be allowed to formally join The Physiological Society, which had been founded in 1876. [42] On 3 July 1915, six women were officially admitted: Florence Buchanan, Winifred Cullis, Ruth C. Skelton, Sarah C. M. Sowton, Constance Leetham Terry, and Enid M. Tribe. [43] The centenary of the election of women was celebrated in 2015 with the publication of the book "Women Physiologists: Centenary Celebrations And Beyond For The Physiological Society." (ISBN 978-0-9933410-0-7)

Prominent women physiologists include:

    , the first woman president of the American Physiological Society in 1975. [44] , [45] along with husband Carl Cori, received the Nobel Prize in Physiology or Medicine in 1947 for their discovery of the phosphate-containing form of glucose known as glycogen, as well as its function within eukaryoticmetabolic mechanisms for energy production. Moreover, they discovered the Cori cycle, also known as the Lactic acid cycle, [46] which describes how muscle tissue converts glycogen into lactic acid via lactic acid fermentation. was rewarded the 1983 Nobel Prize in Physiology or Medicine for the discovery of genetic transposition. McClintock is the only female recipient who has won an unshared Nobel Prize. [47] , [48] along with George Hitchings and Sir James Black, received the Nobel Prize for Physiology or Medicine in 1988 for their development of drugs employed in the treatment of several major diseases, such as leukemia, some autoimmune disorders, gout, malaria, and viral herpes. , [49] along with Richard Axel, received the Nobel Prize in Physiology or Medicine in 2004 for their discovery of odorant receptors and the complex organization of the olfactory system. , [50] along with Luc Montagnier, received the Nobel Prize in Physiology or Medicine in 2008 for their work on the identification of the Human Immunodeficiency Virus (HIV), the cause of Acquired Immunodeficiency Syndrome (AIDS). , [51] along with Carol W. Greider[52] and Jack W. Szostak, was awarded the 2009 Nobel Prize for Physiology or Medicine for the discovery of the genetic composition and function of telomeres and the enzyme called telomerase.

There are many ways to categorize the subdisciplines of physiology: [53]


6: Microbial Physiology - Biology

The sequences of close to 30 microbial genomes have been completed during the past 5 years, and the sequences of more than 100 genomes should be completed in the next 2 to 4 years. Soon, completed microbial genome sequences will represent a collection of >200,000 predicted coding sequences. While analysis of a single genome provides tremendous biological insights on any given organism, comparative analysis of multiple genomes provides substantially more information on the physiology and evolution of microbial species and expands our ability to better assign putative function to predicted coding sequences.

Perhaps no other field of research has been more energized by the application of genomic technology than the field of microbiology. Five years ago, The Institute for Genomic Research published the first complete genome sequence for a free-living organism, Haemophilus influenzae (1). Since then, 27 more microbial genome sequences (2-28) and 3 lower eukaryotic chromosome sequences (29-31) have been published, and at least three times that many sequencing projects are under way. Several important human pathogens are included: Helicobacter pylori (7, 19), Borrelia burgdorferi (12), Treponema pallidum (16), Mycobacterium tuberculosis (15), Rickettsia prowazekii (18), and Chlamydia species (17, 20) the simplest known free-living organism, Mycoplasma genitalium (2) the model organisms, Escherichia coli (8) and Bacillus subtilis (10) Aquifex aeolicus (13) and Thermotoga maritima (21), two thermophilic bacterial species that may represent some of the deepest branching members of the bacterial lineage five representatives of the archaeal domain (3, 9, 11, 14, 28) and the first eukaryote, Saccaromyces cerevisiae (6).

Comparative Genomics

Figure 1. Comparison of amino acid frequency in microbial genomes as a function of % guanine + cytosine (G+C). Panel A: amino acids represented by GC-rich codons panel B: amino acids represented by.

Genomic analyses show a tremendous variability not only in prokaryotic genome size but also in guanine plus cytosine (GC) content, from a low of 29% for B. burgdorferi (12) to a high of 68% for M. tuberculosis (15). The more than twofold difference in GC content affects the codon use and amino acid composition of species. For example, glycine, alanine, proline, and arginine, represented by GC-rich codons, are found at a much higher frequency in the predicted open reading frames from GC-rich genomes (Figure 1). Similarly, isoleucine, phenylalanine, tyrosine, methionine, and aspartic acid, represented by adenine plus thymine (A+T)-rich codons, are found at a higher frequency in the predicted open reading frames from AT-rich genomes. Genome organization also varies among microbial species, from single circular chromosomes to the most unusual situation seen with B. burgdorferi, whose genome is composed of an

1 Mbp (million base pairs) linear chromosome and 21 linear and circular extrachromosomal elements.

Results from the completed prokaryotic genome sequences show that almost half of predicted coding regions identified are of unknown biological function (Table). More unexpectedly, approximately one-quarter of the predicted coding sequences in each species are unique, with no appreciable sequence similarity to any other known protein sequence. These data indicate large areas of microbial biology yet to be understood and suggest that in the microbial world the idea of a model organism may not be valid.

Figure 2. Comparison of the number of predicted coding sequences assigned to biological role categories in seven bacterial and archaeal species.

Functions can be assigned to coding regions by making generalizations about proteins. The number of genes involved in certain functions (transcription and translation, for example) is quite similar, even when genome size differs by fivefold or more (Figure 2). This suggests that a basic complement of proteins is required for certain cellular processes. In contrast, the number of proteins in other function categories--such as biosynthesis of amino acids, energy metabolism, transporters, and regulatory functions--can vary and often increases with genome size (Figure 2). A substantial proportion of the larger microbial genomes represent paralogous genes, that is, genes related by duplication rather than by vertical descent. With few exceptions, the number of total genes that are members of paralogous gene families increases from approximately 12% to 15% in genomes of 1 Mbp up to approximately 50% in genomes of > 3 Mbp. For a given organism, as genome size increases so do functional diversity and biochemical complexity. The one exception with regard to gene duplications is B. burgdorferi, where nearly half the genes in its 1.5-Mbp genome are paralogs. Most paralogous genes in B. burgdorferi are plasmid-encoded genes, many of which are putative lipoproteins. The reason for the large number of paralogous genes in this organism is not known.

The study of transport proteins in prokaryotic species elucidates the relationship between genome size and biological complexity. The ability to discriminate and transport appropriate compounds is an essential function of cell membranes and their resident proteins. The fidelity of these transport reactions is particularly critical at the cytoplasmic membrane of prokayotes since this is the primary barrier that separates the physiologic reactions of the cytosol from the external environment. Many bacterial pathogens face astounding chemical and biological challenges from their host environment (e.g., the extreme acidity of the gastrointestinal tract challenges H. pylori ). In each host-pathogen relationship, the microbial membrane system contributes to the cell's strategy for energy production and carbon fixation while maintaining ionic homeostasis so that the enzymatic activities of the cytosol can proceed. In addition, all species encode proteins to expel toxic ions (particularly metals) and metabolites.

With complete genome sequences, evaluating the quantity and contribution of solute traffic across the membrane boundaries of pathogenic organisms is now possible. Comparisons between 11 sequenced bacterial pathogens (Table) indicate that approximately 6% of each genome encodes proteins (holoenzymes and subunits) involved in solute transport. This percentage is likely an underestimate since many of the gene products annotated as hypothetical proteins have hydropathy profiles reflective of known transporters. Genome size and the number of transport systems are directly related the greatest number, 53, is annotated in the M. tuberculosis genome, and the smallest, 12, is found in the sequence of M. genitalium. Bacterial pathogens are heterotrophs therefore, most of their import systems are used for the uptake of organic compounds (carbohydrates, organic alcohols, acids, amino acids, peptides, and amines). M. tuberculosis is the exception it has 18 annotated transporters for organic substrates and 34 for the movement of ions. In this genome, there are nine copies of a P-type ATPase with a predicted substrate specificity for divalent cations. Whether this reflects a physiologic specialization allowing M. tuberculosis to be more resilient in its host environment is unknown.

Figure 3. Comparison of the transport proteins in two human respiratory pathogens, Haemophilus influenzae en Mycobacterium pneumoniae.

Underlying these general trends are some unique genomic solutions to niche selection and species survival. Two pathogens, H. influenzae en M. pneumoniae, both infect the respiratory tract, yet their strategies for acquiring solutes are distinct (Figure 3). In H. influenzae, the genes encoding transporters show a marked diversification. For example, in systems for amino acid uptake there are transporters for 13 different amino acids as well as proteins for the import of small peptides. These uptake systems work with several metabolic pathways for de novo amino acid synthesis. H. influenzae therefore employs a battery of redundant processes that allow it to optimize survival.

Daarenteen het die M. pneumoniae genome encodes only three transporters with substrate specificity for amino acids. This species, which may have evolved through reductive evolution from a gram-positive ancestor, has discarded all of the genes' encoding enzymes for amino acid biosynthesis (32). Instead of presenting a diverse group of porters for amino acid import, M. pneumoniae presents transport proteins with relatively broad substrate specificity: an oligopeptide transporter a system for the aromatic residues tryptophan, tyrosine, and phenylalanine and the spermidine/putrescine porter. M. pneumoniae uses a generalist strategy of maintaining proteins that are more versatile because of their broad substrate range. These same principles, diversification and redundancy, are repeated in the transport systems for carbohydrates (Figure 3).

In each analyzed genome, transport capacity appears to regulate the metabolic potential of that organism and dictates the range of tissues where a species can reside. Global analysis of transporters within a genome leads to several conclusions of practical consequence. First, culturing of pathogenic organisms is essential for understanding their physiology and for evaluating therapeutic agents. For species such as T. pallidum that have not yet successfully been grown in vitro, transporter analysis provides a clear starting point for the development of a defined culture medium based on information about the range of substrates a given cell can import and metabolize (16). Second, knowledge of transport processes and metabolic pathways they sustain provides novel solutions to the development of antimicrobial agents. An integrated view of cellular biochemistry enables selection of the pathway(s) essential for cell viability. Third, comparisons between genomes elucidate the diverse survival strategies found in pathogens with distinct evolutionary histories.

In addition to transport proteins, other membrane proteins in human pathogens play important roles in cell adhesion and as potential antigenic targets. Perhaps not surprisingly, in most human pathogens whose genome sequencing has been completed, mechanisms for generating antigenic variation on the cell surface have been proposed as a result of genome analysis. The following mechanisms for generating antigenic variation have been described: slipped strand mispairing within DNA sequence repeats found in 5-intergenic regions and coding sequences as described for H. influenzae (1), H. pylori (7), and M. tuberkulose (15) recombination between homologous genes encoding OSPs, as described for M. genitalium (2), M. pneumoniae (5), and T. pallidum (16) and clonal variability in surface-expressed proteins, as described for Plasmodium falciparum (29) and possibly B. burgdorferi (12). Studies of clinical isolates of some species have demonstrated phenotypic variation in the relevant cell surface proteins (33), suggesting that (at least for human pathogens) evolution of antigenic proteins occurs in real time, as cell populations divide.

The Institute for Genomic Research has recently launched the Comprehensive Microbial Resource (CMR), a database designed to facilitate comparative genomic studies on organisms whose genome sequencing has been completed. CMR ( http://www.tigr.org ) includes the sequence and annotation of each of the completed genomes and associated information (such as taxon and Gram stain pattern) about the organisms, the structure and composition of their DNA molecules (such as plasmid vs. chromosome and GC content), and many attributes of the protein sequences predicted from the DNA sequence (such as pI and molecular weight). With CMR, a user can query all the genomes at once or any subset of them, as well as make complex queries based on any properties of the organism or genome. CMR can be used to mine the completed genomes in ways not possible with single genome databases, furthering the progress of comparative genomics.

Evolutionary Studies of Complete Genomes

Studies of complete genomes have provided an unprecedented window into the evolution of life on this planet. For example, analysis of bacterial, archaeal, and eukaryotic genomes has confirmed the uniqueness of the archaeal lineage. Comparative studies of genome sequences have also revealed that lateral gene transfer has been very common over evolutionary time, occurring between both close and distant relatives (21). While the value of genome sequences in studies of evolution has been widely applauded, evolutionary analysis, which can provide great insight into genome sequences, is less well appreciated.

In any comparative biological study, an evolutionary perspective allows one to focus not only on characterizing the similarities and differences between species but also on explaining how and why those similarities and differences may have arisen (34). One area in genome analysis where an evolutionary perspective is useful is in distinguishing similarities due to homology (i.e., common ancestry) from those due to convergence (i.e., a separate origin). An example of the uses of distinguishing convergence from homology is the study of ribosomal RNA (rRNA) genes, which have been cloned from thousands of species comparisons of these gene sequences are used extensively in evolutionary studies of these species. In early studies of rRNA sequences, most thermophiles were noted to have rRNA genes with high GC content relative to mesophiles. Since the rRNA genes in these thermophiles were similar in sequence and not just GC content, many of the thermophiles (e. g., the bacterial genera Aquifex en Thermotoga) were considered closely related. However, recent studies show that these genera are not closely related and the similarities in their rRNA genes are due to convergence (35). The most likely theory is that, to be stable at high temperatures, rRNAs need high GC contents, and therefore, even unrelated thermophiles will have similar sequences because many positions in the rRNA gene will converge to G or C (36). Finding this convergence explains the selective constraints on rRNA genes and shows that these genes may not be the best markers for evolutionary studies of species.

A highly practical use of evolutionary analysis in genome studies is predicting the function of genes (37). Predictions of gene function, a key step in the annotation of genomes, help researchers decide what types of experiments might be useful for a particular species or even a particular gene. Predictions are frequently made by assigning the uncharacterized gene the annotated function of the gene it is most similar to (similarity is measured by a database searching program such as BLAST). However, such predictions are frequently inaccurate because the annotated function may not be the best match (which would lead to error propagation if only the best match were used) and sequence similarity is not the best predictor of function. Several studies have shown that information about the evolutionary relationships of the uncharacterized gene can greatly improve predictions of function. For example, many gene families have undergone gene duplication. Since gene duplication is frequently accompanied by divergence of function, identifying the duplicate lineage (or orthology group) of a particular gene can greatly improve predictions of the gene's function. One orthology identification method is a clustering system developed by Tatusov et al. (38). This method (COG , for clusters of orthologous groups) classifies groups of genes by levels of sequence similarity. Although rapid and accurate in many cases, a clustering method such as COG does not always accurately infer the evolutionary history of genes. For this reason, and because orthologs do not always have the same function, we have developed a phylogenetic-tree-based function prediction method. This method involves inferring the evolutionary relationships of genes and then overlaying onto this history any experimentally determined functions of the genes. For uncharacterized genes, predictions are made according to their position in the tree relative to genes with known functions and according to evolutionary events (such as gene duplications) that may identify groups of genes with similar functions (39). Whatever method is used, information about the evolution of a gene can greatly improve function predictions.

Characterizing the evolutionary history of a particular gene is useful for other reasons. Identifying gene duplication events can provide insight into the mechanisms of gene duplication between genomes (e. g., proximity, age). Comparisons of the evolutionary history of different gene families can be used to infer recombination patterns within species as well as lateral gene transfers between species. While the likelihood of extensive gene transfers between species has thrown our concepts of the evolutionary history of species into disarray (21), identifying particular gene transfer events can be of great practical use. For example, there is a good correlation between regions of genomes responsible for pathogenicity and regions that have undergone lateral gene transfer (40). In analysis of eukaryotic genomes, identifying genes in the nucleus that have been transferred from the organellar genomes can best be done by phylogenetic analysis. Genes derived from the mitochondrial genome should branch most closely with genes from alpha-Proteobacteria, and genes derived from the chloroplast genome should branch most closely with cyanobacterial genes. In most cases, nuclear genes derived from these organelles still encode proteins that function in the organelles.

Evolutionary analysis is also very important for inferring gene loss. For example, we have used phylogenomic analysis to show that the mismatch repair genes MutS en MutL have been lost separately in multiple pathogenic species (e. g., H. pylori, M. tuberkulose, M. genitalium, en M. pneumoniae) (37). Several studies have shown that defects in mismatch repair increase pathogenicity, probably because these defects increase the mutation rate, which allows faster evolutionary response to immune systems and other host defenses. With more and more completed genome sequences, finding any other genes that may have been consistently lost in pathogenic species or strains will be possible. Identifying gene loss can also be useful in making function predictions for genes or species. For example, genes with a conserved association with each other might be lost as a unit--if one is lost, there is probably not much reason for the others to persist. The correlated presence and absence of genes constitute the basis of the phylogenetic profiles method of Pellegrini et al. (41), a very important tool in predicting functions.

The study of the evolutionary relationship of the M. tuberkulose complex has been greatly enhanced by the availability of two complete sequences from different strains (15 and www.tigr.org) and most sequences from the M. bovis genome ( http://www.sanger.ac.uk ). The H37Rv laboratory strain of M. tuberkulose was first isolated in 1905 and has been passed for many decades substantial differences have been demonstrated between recent clinical isolates and genomes of laboratory strains with long histories of passage. A highly infectious clinical isolate of M. tuberkulose, CDC1551, was involved in a recent cluster of tuberculosis cases in the United States (42). Whole genome analysis of single nucleotide polymorphisms, insertions and deletions, and gene duplications provides comparisons that were previously unobtainable. Studies examining a limited set of M. tuberkulose genes from various strains suggest a limited sequence diversity between strains and in the complex, with a nucleotide polymorphism rate of approximately 1 in 10,000 bp (43). Detailed comparison of strains H37Rv and CDC1551 indicates a higher frequency of polymorphism, approximately 1 in 3,000 bp, with approximately half the polymorphism occurring in the intergenic regions. In other words, 50% of the polymorphisms are in 10% of the genome. While this rate is higher than that suggested (43), it still represents a lower nucleotide diversity than found in limited comparisons from other pathogens.

Examination of insertion and deletion events and gene duplication between species and strains allows insight into the evolutionary relationship of the M. tuberkulose kompleks. For example, a phospholipase C region, present in CDC1551 and absent in H37Rv, is also present in M. bovis. The simplest explanation for this is that the common ancestor of M. tuberkulose en M. bovis contained this region, and the region was subsequently deleted in the H37Rv lineage.

Figure 4. Polymorphic insertions in Mycobacterium tuberculosis. A genomic region containing membrane lipid protein genes likely to have arisen through gene duplication. H37Rv contains two genes (Rv2543 en Rv2544), while the homologous region.

Membrane lipid proteins are identified by a unique signature sequence that is the target for a specific lipoprotein signal peptidase and that allows the cleaved protein product to attach by cysteinyl linkage to a glyceride-fatty acid lipid. Among the genes encoding membrane lipid proteins in strain H37Rv are two in tandem (Rv2543 and Rv2544). Nucleotide identity of >85% suggests that these two genes arose through duplication. The homologous genome region in strain CDC1551 contains the orthologs MT2618 and MT2620, respectively, as well as a third gene, MT2619, which by sequence similarity appears to represent an additional duplication (Figure 4). The increased induction of cytokines by CDC1551 is associated with the membrane lipid component (42). Modification of the lipid component by various protein components may contribute to differences in the immune response to M. tuberculosis infection in the host.

These examples illustrate how evolutionary information can benefit genome analysis. Complete genome sequences are also very useful. Gene loss, for example, cannot be readily identified without knowing the complete genome sequence of an organism. Since there are feedback loops between evolutionary and genome analyses, combining them into a single composite phylogenomic analysis may be advantageous (37, 44). As more and more genomes are completed, the benefits of combined evolutionary and genome analysis should become even more apparent.

Dr. Fraser is president and director of the Institute for Genomic Research. She is involved in genome analysis of microbial species and the use of comparative genome analysis in elucidating species diversity.


Tobias Dörr, Partick J. Moynihan, Christoph Mayer

Bacterial cells are encased in a cell wall, which is required to maintain cell shape and to confer.

Keywords: Bacterial cell wall,­Peptidoglycan synthesis,­cell wall dynamics,­Cell wall turnover,­Cell wall modification,­Peptidoglycan recycling,­Autolysins,­Cell wall degradation,­antibiotic target


Biology jobs

The Sr. Scientist will lead biology discovery efforts supporting structure-based drug discovery in targeted oncology programs.

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  • Salary commensurate with experience.
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Reproductive medicine, biology, and genetics.

Postdoctoral Researcher (m/f/d) autoimmunity and aging

BioMed X Institute will establish a new research group in the field of autoimmunity and aging

Biologist

  • 11785 Beltsville Drive, Beltsville, Maryland 20705
  • $103,690 to $134,798 per year
  • Food and Drug Administration / Center for Tobacco Products

This Direct-Hire position is in the Food and Drug Administration and is located in the Center for Tobacco Products (CTP), Office of Science (OS)

Postdoctoral Position – Influence of Diet & Exercise on the Sperm Epigenome

  • San Antonio, Texas
  • Commensurate with experience
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College of Sciences, Department of Biology - McCarrey Lab

Postdoctoral fellowship in cancer computational biology

After your PhD in bioinformatics, data analysis or theory, how about exploring quantitative principles to explain and treat tumor heterogeneity?

Postdoctoral Associate

  • Albany, New York (US)
  • Commensurate with experience
  • Research Foundation for SUNY

Research Foundation for SUNY is seeking a Postdoctoral Associate to contribute to our research program in bacterial population genomics and evolution.

Postdoc in Synthetic Biology of Natural Products

  • Denmark (DK)
  • Agreement with the Danish Confederation of Professional Associations
  • DTU

If your field of expertise is within natural products, chemistry, discovery or biosynthesis - this is your chance.

Postdoc in Yeast Synthetic Biology

  • Denmark (DK)
  • Collective agreement with the Danish Confederation of Professional Associations
  • [email protected]

Do you want freedom and funding to break new ground to the benefit of mankind? If your field of expertise is within metabolic engineering/synthetic.

Postdoctoral Fellow

The Subramanian group seeks highly motivated Postdoctoral candidates interested in autoimmunity, infectious disease and host-pathogen interactions.

Postdoctoral Fellow

The Subramanian group seeks a computationally-oriented Postdoctoral Fellow interested in immunology, infectious disease and host-pathogen interactions

Postdoctoral Researcher - Bioinformatics

  • San Francisco, Kalifornië
  • Commensurate with experience
  • University of California, San Francisco (UCSF)

The lab of Professor Nevan Krogan at the University of California, San Francisco

Postdoctoral Position (m/f/d) Protective Tissue Factors in Autoimmune Diseases

  • Heidelberg, Baden-Württemberg (DE)
  • Competitive salaray
  • BioMed X Research Institute

3D tissue modelling and cell culture (spheroids, organoids, hydrogels, bio-scaffolds, organ-on-a-chip/microfluidics / bioprinting-based tissue models)

Postdoctoral scholars working on transcriptional and epigenetic control of metabolism

  • Berkeley, California (US)
  • The annual salary range for this position is $54,430 to $58,608 with generous benefits
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Transcriptional and epigenetic basis of adipose metabolic control using mouse models and mechanistic studies in vitro and in vivo.

Postdoctoral Research Associate Position

  • Chicago, Illinois
  • Appointments and salary are commensurate with research experience
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Postdoctoral Research Associate position is available immediately for a highly motivated individual to investigate.

Postdoctoral Associate (Epigenetics of Aging and Cancer) Adams Lab

Dr. Adams’ lab investigates the impact of chromatin and epigenetics on cellular senescence, aging and cancer.

Post-doctoral fellowship in genetics and functional genomics of cardiovascular disease

  • Stanford, California (US)
  • Minimum $65,500 + benefits, commensurate with experience.
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Seeking highly collaborative postdoctoral fellows with experience in transcriptional regulatory mechanisms, cell biology and cardiovascular disease.

Postdoctoral Researcher

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Rosenthal laboratory of the Bell Center at the Marine Biological Laboratory (MBL) in Woods Hole, MA.

Postdoctoral Researcher

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The Center for Translational Research in Infection and Inflammation (CTRII) located within Tulane University School of Medicine

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The Postdoctoral Research Associate in biological sciences for fundamental research on pain in rodents.

Faculty Positions in Synthetic Biology, Microbial Physiology and Ecology, Biochemistry

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  • International competitive salary
  • Northeastern University

Faculty Positions in Synthetic Biology, Microbial Physiology and Ecology, Biochemistry Electrobiomaterials Institute at Northeastern University inv.

Faculty Positions in Synthetic Biology, Microbial Physiology and Ecology, Biochemistry

  • Shenyang, Liaoning (CN)
  • Competitive salary and fringe benefits
  • Northeastern University

Faculty Positions in Synthetic Biology, Microbial Physiology and Ecology, Biochemistry Electrobiomaterials Institute at Northeastern University inv.


What is Microbial Diversity?

Microbes are one of the dominant life forms which occur in the universe, but most of us are ignorant of their true profile. This is perhaps because they are so tiny as to be visible to the naked eye. For this reason only, they remained unknown till about 300 years ago.

Microbiology is the study of living organisms of microscopic size which include bacteria, fungi, algae, protozoa and infectious agents at the border line of life that are called viruses. This science is concerned with their form, structure, reproduction, physiology, metabolism and classification.

It includes their distribution in nature, their relationship with each other and other living organisms, their effects on human beings and other animals and plants. Again, it comprises their ability to make physical and chemical changes in the environment and their relationship to physical and chemical agents.

Since these organisms are out of sight of the common man for many reasons, their contributions not only to our lives but also to this earth have not been properly appreciated. The only aspect of their myriad actions that gets highlighted is their potential to cause misery, disease and injury.

On the other hand, they are closely associated with the health and welfare of human beings. Microbes are involved in the making of curd, cheese, butter, and wine, in the production of antibiotics like penicillin, manufacture of organic acids, alcohols and processing of domestic and industrial wastes. Rarely, a moment passes when the beneficial or harmful effect of microbes does not influence the mankind.

Microbes are typically unit or multicultural microscopic organisms, which are cosmopolitan in their distribution, i.e. they are widely distributed in air, water, soil, sea, mountains, hot springs and also in bodies of living plants and animals including the human.

They are present profusely in the natural and manmade world. These organisms have a high degree of adaptability. Thus, the microbes constitute the world of their own, full of uniqueness from various biological view points.

Microorganisms are exceptionally attractive models for studying fundamental life processes. They can be easily grown in culture tubes or flasks, thereby requiring less space and maintenance than larger plants and animals.

Their growth rate is very fast and also they reproduce at brisker pace than many other life forms. For example, under suitable conditions, some species of bacteria can undergo almost 100 generations in 24-hour period. The metabolic processes of microbes follow the pattern that occurs in higher plants and animals.

The unicellular yeasts utilize glucose in essentially the same manner as cells of mammalian tissue, the same system of enzymes are also involved. The energy liberated in the breakdown of glucose is trapped and later used for the vital activities of the cells, whether they are bacteria, yeast, protozoa or muscle cells.

Plants are characterized by their ability to utilize the solar energy, where as the animals require chemical substances for their life processes. In this respect, some microbes are like plants, others like animals and certain others have the unique ability to behave as plants as well as animals.

In microbiology, the organisms can be studied in great detail and their life processes can be observed while they are actively metabolizing, growing, reproducing, aging and dying. By modifying their environment, their metabolic activities can be altered, growth becomes regulated and it may even change their genetic patterns. All these can study without causing any harm to the organism.


Kyk die video: Класс Млекопитающие анатомия, физиология. Биология 7 класс #39. Инфоурок (September 2022).