Responses of Pseudomonas putida to phenol-induced metabolic and stress signals
Date
2008-10-30T13:21:53Z
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Abstract
Käesolev doktoriväitekiri keskendub erinevatele signaalidele, mida tajub mullabakter Pseudomonas putida kokkupuutes aromaatse süsinikuühendiga fenool. P. putida on võimeline kasutama fenooli ainsa süsiniku- ja energiaallikana plasmiidse pheBA operoni ja kromosomaalse katehholi lagundamist võimaldava raja koosavaldumisel. Töö esimeseks eesmärgiks oli selgitada, milliste mehhanismide abil toimub pheBA promootorilt lähtuva transkriptsiooni pärssimine erinevates kasvukeskkondades. Keskonnas toimuvate muutuste tunnetamiseks kasutavad bakterid kahekonponendilisi signaaliülekande süsteeme. Minu teiseks töö eesmärgiks oli uurida signaaliülekande süsteemi ColRS rolli bakteris P. putida, täpsemalt selle seost rakkude fenoolitaluvusega.
Doktoritöö osas, mis puudutab fenooli lagundamist võimaldavate geenide ekspressiooni, selgus, et aminohapete juuresolekul toimub pheBA operoni ekspressiooni pärssimine Crc valgu vahendusel. Uurimistöö teise osa andmed viitavad selle, et ColRS süsteem reguleerib bakterirakkude membraani läbitavust ja osaleb seetõttu fenoolitolerantsuse tagamises. Lisaks näitavad töö tulemused, et funktsionaalse ColRS süsteemi puudumine põhjustab rakkudele stressi ka glükoosi tardsöötmel. Kokkuvõtvalt näitasid käesoleva töö tulemused, et fenoolist tulenevad signaalid bakteris P. putida sõltuvad tugevalt nii fenooli kontsentratsioonist kui ka teistest keskkonnatingimustest.
This study concentrates on different phenol-induced signals that are sensed by soil bacterium Pseudomonas putida. P. putida is able to degrade a wide variety of aromatic compounds. Coordinated expression of the plasmid-originated pheBA genes and the chromosomal catechol degradation pathway enables P. putida to degrade phenol and use it as a growth substrate. First, the study focuses on the mechanisms, which negatively affect transcription of the phenol degradation operon in P. putida. Many bacterial adaptive responses to environmental changes are controlled by two-component signal transduction systems. To unravel the function of ColRS two-component signal transduction pathway, the second part the thesis concentrates on the elucidation of the functions of the ColRS system and particularly on its role in phenol tolerance of P. putida. Study of regulation of phenol degradation genes showed that repressive effect on expression of pheBA genes caused by amino acids in the growth medium is mediated by Crc protein. In the second part of my thesis I show that ColRS system participates in phenol tolerance of P. putida and in addition the colR-deficient strain experiences serious stress on glucose medium. Altogether the study shows, that the nature of the phenol-induced signals, which are sensed by P. putida, strongly depend on the concentration of phenol in the medium as well as other growth conditions.
This study concentrates on different phenol-induced signals that are sensed by soil bacterium Pseudomonas putida. P. putida is able to degrade a wide variety of aromatic compounds. Coordinated expression of the plasmid-originated pheBA genes and the chromosomal catechol degradation pathway enables P. putida to degrade phenol and use it as a growth substrate. First, the study focuses on the mechanisms, which negatively affect transcription of the phenol degradation operon in P. putida. Many bacterial adaptive responses to environmental changes are controlled by two-component signal transduction systems. To unravel the function of ColRS two-component signal transduction pathway, the second part the thesis concentrates on the elucidation of the functions of the ColRS system and particularly on its role in phenol tolerance of P. putida. Study of regulation of phenol degradation genes showed that repressive effect on expression of pheBA genes caused by amino acids in the growth medium is mediated by Crc protein. In the second part of my thesis I show that ColRS system participates in phenol tolerance of P. putida and in addition the colR-deficient strain experiences serious stress on glucose medium. Altogether the study shows, that the nature of the phenol-induced signals, which are sensed by P. putida, strongly depend on the concentration of phenol in the medium as well as other growth conditions.