ColR-ColS signalling system and transposition of Tn4652 in the adaptation of Pseudomonas putida
Date
2010-12-22
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Abstract
Kõik elusorganismid peavad ellujäämise nimel kohanema ümbritseva keskkonnaga, mis võib pidevalt muutuda. Bakterid on silmale nähtamatud ainuraksed organismid, kes suudavad ellu jääda ka nii äärmuslikes tingimustes nagu kuumaveeallikad, ookeani süvikud, polaarjää jne. Bakteriperekond Pseudomonas on tuntud oma hea kohanemisvõime poolest, mis laseb neil asustada erinevaid keskkondi nagu muld, vesi, taimed, loomad ja ka inimene. Nimetatud perekonna liikmed suudavad kohaneda ka antibiootikumidega, mis tekitab probleeme nüüdisaegses meditsiinis. Pseudomonas aeruginosa on osutunud ravile allumatuks bakteriks, kuna suudab taluda mitmeid antibiootikume. Mikroobi kohanemine keskkonnaga toimub läbi füsioloogiliste või geneetiliste muutuste. Bakteriraku füsioloogias toimuvaid muutusi kutsuvad esile erinevad signaalsüsteemid, mis tajuvad keskkonna vaheldumist. Geneetiline kohandumine uute tingimustega on pikaajalisem ja järglastele edasi kanduv, kuna muutused toimuvad organismi genoomis. Käesolev töö on keskendunud bakteriperekonna Pseudomonas osava kohanemise tagamaade selgitamisele ohutu keskkonnabakteri Pseudomonas putida näitel. Antud töö uurib signaalsüsteemi, mida on seostatud mitmesuguste protsessidega nagu virulentsuse, mutatsiooniprotsesside, antibiootikumide ja raskemetallide resistentsusega ning mikroobi võimega asustada taimejuuri. Minu tööst selgub, et uuritud signaaliraja peamiseks märklauaks on bakterirakku ümbritsev membraan, kusjuures mõjutatud on nii membraanis paiknevad valgud kui ka lipiidid ja samuti rakku toetav sein ning kaitsev kapsel. Need tulemused selgitavad, kuidas suudab üks signaalirada vahendada muutusi erinevates protsessides ja seeläbi osaleda bakteriraku kohanemises.
Survival of living organisms depends on their ability to adjust to the environment. Bacteria are unicellular organisms occupying harsh environments including extreme temperature, acid, pressure, etc. Pseudomonas genus is extraordinary because its ability to adapt as the representatives of this family are found in soil, water, or colonising organisms such as plants, animals and humans. Most notorious member of the family is Pseudomonas aeruginosa who can cope with several antibiotics and thus causes clinical problems to humans. Bacterial adjustment to environment can be either physiological or genetic. Physiological adaptation takes place during the lifetime of an organism and is mediated through some kind of signalling systems that monitor environmental conditions. Genetic adaptation is maintained in a population over many generations as it occurs through the changes in the genome. This thesis studied the mechanisms of physiological and genetic adaptation of Pseudomonas bacteria, whereas the human friendly species P. putida was used for the safety measures. This thesis concentrated on a conserved signalling system regulating various processes of Pseudomonas bacteria such as root colonisation, virulence, resistance to heavy metals and some antibiotics, phenol tolerance, mutational processes, and cell death. My work revealed the connection between such different processes. Namely, the current signalling system is regulating membrane functioning and thus can be considered as the sentinel of bacterial cell envelope. Different membrane compartments are affected, for example membrane proteins and lipids, as well as the peptidoglycan cell wall and polysaccharide capsule explaining how one signalling system can affect several aspects of bacterial adaptation and fitness.
Survival of living organisms depends on their ability to adjust to the environment. Bacteria are unicellular organisms occupying harsh environments including extreme temperature, acid, pressure, etc. Pseudomonas genus is extraordinary because its ability to adapt as the representatives of this family are found in soil, water, or colonising organisms such as plants, animals and humans. Most notorious member of the family is Pseudomonas aeruginosa who can cope with several antibiotics and thus causes clinical problems to humans. Bacterial adjustment to environment can be either physiological or genetic. Physiological adaptation takes place during the lifetime of an organism and is mediated through some kind of signalling systems that monitor environmental conditions. Genetic adaptation is maintained in a population over many generations as it occurs through the changes in the genome. This thesis studied the mechanisms of physiological and genetic adaptation of Pseudomonas bacteria, whereas the human friendly species P. putida was used for the safety measures. This thesis concentrated on a conserved signalling system regulating various processes of Pseudomonas bacteria such as root colonisation, virulence, resistance to heavy metals and some antibiotics, phenol tolerance, mutational processes, and cell death. My work revealed the connection between such different processes. Namely, the current signalling system is regulating membrane functioning and thus can be considered as the sentinel of bacterial cell envelope. Different membrane compartments are affected, for example membrane proteins and lipids, as well as the peptidoglycan cell wall and polysaccharide capsule explaining how one signalling system can affect several aspects of bacterial adaptation and fitness.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
dissertatsioonid, bioloogia, bakterid, bakterid, kohastumine, Pseudomonas putida