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Most of the bacteria live in unstable environments and their successful survival requires adaptive responses to constantly changing conditions. Bacteria use two-component signal transduction pathways to sense the external environment and to coordinate cellular events according to changing conditions. Mostly, the signals from environment change the expression of genes involved in regulation of physiology. However, genetic adaptation is also shown to be regulated by signal transduction network. The idea of genetic change as a regulated biological function is quite recent and fundamentally different from thinking about genetic change as the stochastic processe. Therefore, this field of studies is highly debated and full of controversies. Our previous study has shown that activity of P. putida transposon Tn4652 depends on physiological state of the host being activated in the stationary phase. Our recent investigation has revealed the importance of ColR-ColS two-component signal transduction system in activation of transposition of Tn4652 in starving P. putida. Moreover, our unpublished results suggest that ColRS might be involved in more general regulation of mutational processes because ColR seems to be necessary also in accumulation of point mutations. Therefore, we hypothesize that ColRS two-component system may regulate some DNA metabolism gene(s). So far, the signal molecule sensed by ColS and the target genes of ColR are not identified. We are intending to enlighten molecular mechanisms underlying the ColR-ColS-regulated DNA rearrangements in P. putida. We plan to identify of target genes regulated by ColR-ColS two-component system and study the target site selection of Tn4652 which is hypothesized to be regulated by ColR. We will examine whether ColR is responsible for triggering of transposition and other mutational processes specifically under stressful conditions. Also, we intend to test the hypothesis that ColR might be involved in bacterial communication. Results obtained from the proposed studies would widen our awareness of bacterial signal transduction network regulating genetic adaptation of bacteria. |