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2865491 
Journal Article 
Homologous recombination is facilitated in starving populations of Pseudomonas putida by phenol stress and affected by chromosomal location of the recombination target 
Tavita, K; Mikkel, K; Tark-Dame, M; Jerabek, H; Teras, R; Sidorenko, J; Tegova, R; Tover, A; Dame, RT; Kivisaar, M 
2012 
1 
Mutation Research
ISSN: 0027-5107
EISSN: 1873-135X 
737 
1-2 
12-24 
English 
22917545 
WOS:000309636900003 
Homologous recombination (HR) has a major impact in bacterial evolution. Most of the knowledge about the mechanisms and control of HR in bacteria has been obtained in fast growing bacteria. However, in their natural environment bacteria frequently meet adverse conditions which restrict the growth of cells. We have constructed a test system to investigate HR between a plasmid and a chromosome in carbon-starved populations of the soil bacterium Pseudomonas putida restoring the expression of phenol monooxygenase gene pheA. Our results show that prolonged starvation of P. putida in the presence of phenol stimulates HR. The emergence of recombinants on selective plates containing phenol as an only carbon source for the growth of recombinants is facilitated by reactive oxygen species and suppressed by DNA mismatch repair enzymes. Importantly, the chromosomal location of the HR target influences the frequency and dynamics of HR events. In silico analysis of binding sites of nucleoid-associated proteins (NAPs) revealed that chromosomal DNA regions which flank the test system in bacteria exhibiting a lower HR frequency are enriched in binding sites for a subset of NAPs compared to those which express a higher frequency of HR. We hypothesize that the binding of these proteins imposes differences in local structural organization of the genome that could affect the accessibility of the chromosomal DNA to HR processes and thereby the frequency of HR. 
Homologous recombination in stationary-phase bacteria; Pseudomonas putida; Reactive oxygen species; Phenol stress; Nucleoid-associated proteins; Accessibility of chromosomal DNA