Fis regulates Pseudomonas putida biofilm formation by controlling the expression of lapA
Kuupäev
2018-05-17
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Bakterid elavad looduses valdavalt biofilmis, pinnale kinnituvate bakterite kogumis. Biofilmis elamisel on bakterite jaoks mitmeid eeliseid. Biofilmis elavad bakterid on kahjulike keskkonnamõjude eest paremini kaitstud ja heades tingimustes aitab pinnale kinnitumine nendesse tingimusesse jäädagi. Biofilm ei ole kasulik mitte ainult bakteritele, vaid paljud biofilmi moodustavad bakterid on vajalikud ka taimedele. Üheks selliseks bakteriks on Pseudomonas putida, mida uurin oma doktoritöös. P. putida moodustab biofilmi taime juurtel ja kaitseb taimi, ka põllumajanduslikult olulisi kultuure, haigustekitajate eest ning soodustab nende kasvu.
Käesoleva töö käigus leiti juhuslikult, et P. putida biofilmi mõjutab bakteri keskne regulaatorvalk Fis. Kui bakterid satuvad headesse tingimustesse, siis Fis-i roll on suunata nad kiirelt kasvama ja kui toitained saavad otsa, siis aeglustada kasv jälle maha. Me nägime, et liiga palju Fis-i tootvad bakterid ei suuda ringi liikuda. Sealt tekkis kahtlus, et äkki nad ei liigu sellepärast, et jäävad hoopis paigale ja moodustavad biofilmi. See teooria osutus tõeseks ja püstitas kohe järgmise küsimuse, kuidas Fis suunab bakterid biofilmi moodustama? Me leidsime, et Fis soodustab ühe väga suure kleepvalgu tootmist. See kleepvalk, LapA, on biofilmi tekkeks väga oluline, kuna võimaldab bakteritel nii pinnale kui teineteisega kleepuda. Käesolevas töös näitasime, et Fis seondub kahes kohas lapA geeni ette ja just neid kohti kasutades soodustab LapA tootmist. Lisaks kirjeldasime need kohad (promootorid), kust algab lapA mRNA tootmine. Kui tavaliselt on ühel geenil üks või kaks promootorit, siis lapA geenil on neid lausa kuus.
Kokkuvõttes lõi see töö uusi teadmisi P. putida biofilmi regulatsioonist ja aitab seega paremini mõista selle kasuliku mullabakteri elu väga olulist etappi.
Biofilms are the prevailing lifestyle of bacteria in most natural environments. This is because living in a biofilm gives bacteria a number of advantages. When the environment is hazardous, residing in a biofilm protects them; and when conditions are favourable, biofilm is a way to settle down and not be carried away from the good life. Biofilm is not only useful for bacteria but many biofilm-forming bacteria are also beneficial for plants. One of those beneficial bacteria is Pseudomonas putida, the focus of this thesis. P. putida forms biofilm on roots of plants, including agriculturally important crops, protecting them against disease-causing microorganisms and promoting plant growth. During this work, it was discovered that P. putida’s biofilm is regulated by the central regulator protein Fis. Fis is the regulator that starts fast growth in good conditions and when nutrients deplete, decelerates growth. We saw that bacteria producing elevated levels of Fis were unable to move around. This prompted the idea that maybe they are not moving because they are settling down and forming biofilm. This idea proved true and raised the next question, how does Fis lead the bacteria to form biofilm? We found that Fis upregulates the production of a huge adhesion protein. This protein, LapA, is a key factor for biofilm formation as it enables bacteria to stick both to surfaces and to one another. In this work, we show that Fis binds upstream of the lapA gene in two positions and utilizes these sites to boost the production of LapA. We also described the location of the promoter sites where the production of lapA mRNA is initiated. While many genes have one or two promoter, lapA has surprisingly many – six. Altogether, this work shed light onto P. putida biofilm regulation and thus helps us better understand a very important stage in this beneficial soil bacterium’s life.
Tartu Ülikool. Loodus- ja täppisteaduste valdkond
Biofilms are the prevailing lifestyle of bacteria in most natural environments. This is because living in a biofilm gives bacteria a number of advantages. When the environment is hazardous, residing in a biofilm protects them; and when conditions are favourable, biofilm is a way to settle down and not be carried away from the good life. Biofilm is not only useful for bacteria but many biofilm-forming bacteria are also beneficial for plants. One of those beneficial bacteria is Pseudomonas putida, the focus of this thesis. P. putida forms biofilm on roots of plants, including agriculturally important crops, protecting them against disease-causing microorganisms and promoting plant growth. During this work, it was discovered that P. putida’s biofilm is regulated by the central regulator protein Fis. Fis is the regulator that starts fast growth in good conditions and when nutrients deplete, decelerates growth. We saw that bacteria producing elevated levels of Fis were unable to move around. This prompted the idea that maybe they are not moving because they are settling down and forming biofilm. This idea proved true and raised the next question, how does Fis lead the bacteria to form biofilm? We found that Fis upregulates the production of a huge adhesion protein. This protein, LapA, is a key factor for biofilm formation as it enables bacteria to stick both to surfaces and to one another. In this work, we show that Fis binds upstream of the lapA gene in two positions and utilizes these sites to boost the production of LapA. We also described the location of the promoter sites where the production of lapA mRNA is initiated. While many genes have one or two promoter, lapA has surprisingly many – six. Altogether, this work shed light onto P. putida biofilm regulation and thus helps us better understand a very important stage in this beneficial soil bacterium’s life.
Tartu Ülikool. Loodus- ja täppisteaduste valdkond
Kirjeldus
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Märksõnad
biological film, bacterial proteins, transcription factors