Different spectra of stationary-phase mutations in early-arising versus late-arising mutants of Pseudomonas putida: involvement of the DNA repair enzyme MutY and the stationary-phase sigma factor RpoS.
Stationary-phase mutations occur in populations of stressed, nongrowing, and slowly growing cells and allow mutant bacteria to overcome growth barriers. Mutational processes in starving cells are different from those occurring in growing bacteria. Here, we present evidence that changes in mutational processes also take place during starvation of bacteria. Our test system for selection of mutants based on creation of functional promoters for the transcriptional activation of the phenol degradation genes pheBA in starving Pseudomonas putida enables us to study base substitutions (C-to-A or G-to-T transversions), deletions, and insertions. We observed changes in the spectrum of promoter-creating mutations during prolonged starvation of Pseudomonas putida on phenol minimal plates. One particular C-to-A transversion was the prevailing mutation in starving cells. However, with increasing time of starvation, the importance of this mutation decreased but the percentage of other types of mutations, such as 2- to 3-bp deletions, increased. The rate of transversions was markedly elevated in the P. putida MutY-defective strain. The occurrence of 2- to 3-bp deletions required the stationary-phase sigma factor RpoS, which indicates that some mutagenic pathway is positively controlled by RpoS in P. putida.
Saumaa
Signe
S
Department of Genetics, Institute of Molecular and Cell Biology, Tartu University and Estonian Biocentre, Estonia.
Tover
Andres
A
Kasak
Lagle
L
Kivisaar
Maia
M
D001426:Bacterial Proteins / Q000502:physiology*; D001483:Base Sequence; D045647:DNA Glycosylases; D004260:DNA Repair; D004251:DNA Transposable Elements; D008969:Molecular Sequence Data; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000502:physiology*; D011401:Promoter Regions, Genetic; D016958:Pseudomonas putida / Q000235:genetics* / Q000254:growth & development; D012808:Sigma Factor / Q000502:physiology*
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase