Signals and responses of ColRS two-component system in Pseudomonas putida
Date
2020-07-10
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Abstract
Baktereid võib leida peaaegu kõikjalt. Osad neist on kohastunud elama mullas, teised jällegi veekeskkonnas, taimede pinnal, nahal või elusorganismide sees. Vabas looduses elavate bakerite elutingimused on tihti muutuvad. Näiteks temperatuur võib muutuda tundidega, toitaineid võib mõnel päeval olla külluses, teisel jällegi peaaegu üldse mitte või muutub ümbritseva keskkonna pH bakterite enda elutegevuse tõttu.
Selleks, et aru saada, millised on täpselt tingimused nende ümber, kasutavad bakterid kahest valgust koosnevaid signaaliradu. Üks valkudest, sensorvalk, paikneb enamasti bakteri pinnal ning tunnetab teatud tingimuse või signaali olemasolu. Vastusena signaali äratundmisele aktiveerib sensorvalk teise valgu, regulaatorvalgu. Regulaator asub bakteri sees ning aktiveerituna kutsub esile muutused bakteri füsioloogias muutes näiteks geenide avaldumist.
Käesolevas töös uuriti ühte taime- ja mullabakterites leiduvat kahekomponentset süsteemi – ColRS süsteemi, mis on oma nime saanud sellest, et ta aitab bakteril taimejuuri koloniseerida. Me leidsime, et mullabakteris Pseudomonas putida reageerib ColRS süsteem tsingi, raua, mangaani ja kaadmiumi liiale väliskeskkonnas. Kuigi tsink, raud ja mangaan on bakterile vajalikud metallid on nende liigne kogus kahjulik, sest metalliioonid võivad kahjustada bakteri membraani, valke või ka DNA-d. ColRS süsteemi puudumisel on P. putida oluliselt tundlikum tsingi ja raua liiale ja veidi tundlikum mangaani liiale. Seetõttu arvame, et ColRS süsteemi ülesandeks on tunnetada eelkõige tsingi ja raua liia olemasolu.
Varasemad uuringud osundasid, et ColRS süsteem on P. putida-le vajalik membraani terviklikkuse säilimiseks. Ka antud töö tulemused viitavad, et ColRS süsteemi olulisus tsingiliias peitub membraanikahjustuste ärahoidmises. ColRS süsteemi aktivatsioon kutsub P. putida-s esile vastuse, mis tagab membraani terve püsimise ning seeläbi takistab tsingi- ja rauaioonide sisenemist bakterirakku
Bacteria can be found almost everywhere. Some of them are adapted to life in soil, while others feel themselves at home in water, on plants, inside the gut or on the skin. In nature, the conditions around bacteria are constantly changing. For example, the temperature can change within hours, the nutrients can be sufficient in one day and deprived in other and the pH in the environment can be shifted due to the byproducts of the bacteria themselves. To determine the conditions around them, bacteria use signaling systems consisting of two proteins. The first protein, histidine kinase, is usually located at the surface of the bacterium and detects the presence of a certain signal or condition. In response to detecting the signal, the histidine kinase activates another protein, the response regulator. Response regulator is inside the bacterium and in an active state changes the physiology of the bacterium by altering, for example, gene expression. The focus of this thesis was one two-component system that can be found in soil and plant bacteria – the ColRS system, named after being necessary for colonizing plant roots. We found that for soil bacterium Pseudomonas putida this system detects the presence of excess amount of zinc, iron, manganese and cadmium in the extracellular environment. Although, zinc, iron and manganese are necessary for bacteria, their excess is harmful. Metal ions can damage the membrane of the bacterium, its proteins and also its DNA. If the ColRS system is absent in P. putida, it is sensitive to zinc and iron and has a slightly decreased tolerance for manganese. Therefore, we propose that the main role of the ColRS system is to sense the excess of zinc and iron. Previous studies with the ColRS system have indicated that the system is required for maintaining membrane integrity. The results of this thesis also suggest that the importance of ColRS system in zinc excess lies in preventing membrane damage. The activation of the ColRS system induces a response that helps to maintain membrane integrity and thereby prevents the metal ions from entering the cell.
Bacteria can be found almost everywhere. Some of them are adapted to life in soil, while others feel themselves at home in water, on plants, inside the gut or on the skin. In nature, the conditions around bacteria are constantly changing. For example, the temperature can change within hours, the nutrients can be sufficient in one day and deprived in other and the pH in the environment can be shifted due to the byproducts of the bacteria themselves. To determine the conditions around them, bacteria use signaling systems consisting of two proteins. The first protein, histidine kinase, is usually located at the surface of the bacterium and detects the presence of a certain signal or condition. In response to detecting the signal, the histidine kinase activates another protein, the response regulator. Response regulator is inside the bacterium and in an active state changes the physiology of the bacterium by altering, for example, gene expression. The focus of this thesis was one two-component system that can be found in soil and plant bacteria – the ColRS system, named after being necessary for colonizing plant roots. We found that for soil bacterium Pseudomonas putida this system detects the presence of excess amount of zinc, iron, manganese and cadmium in the extracellular environment. Although, zinc, iron and manganese are necessary for bacteria, their excess is harmful. Metal ions can damage the membrane of the bacterium, its proteins and also its DNA. If the ColRS system is absent in P. putida, it is sensitive to zinc and iron and has a slightly decreased tolerance for manganese. Therefore, we propose that the main role of the ColRS system is to sense the excess of zinc and iron. Previous studies with the ColRS system have indicated that the system is required for maintaining membrane integrity. The results of this thesis also suggest that the importance of ColRS system in zinc excess lies in preventing membrane damage. The activation of the ColRS system induces a response that helps to maintain membrane integrity and thereby prevents the metal ions from entering the cell.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
signal molecules, signal transduction, stress tolerance, metals