engleski

mutS-Dependent GASP Phenomenon in Mixed Cultures of Escherichia coli and Salmonella enterica

The major mechanisms of microbial genome ecological specialization are the loss of preexisting genes or gene activities during evolution. The ability of Escherichia coli to grow during carbon starvation in stationary phase has been termed the Growth Advantage in Stationary Phase (GASP) phenotype. The GASP phenomenon has been observed in range of microorganisms, including clinical isolates of E. coli and S. enterica. The occurrence of mutators among isolates of E. coli and S. enterica is up to 10%. The resulting mutants with increased fitness express GASP phenotype enabling them to grow and displace the parent as the majority population. The amount of MutS, homodimer which binds to mismatched bases, is strongly down regulated as E. coli cells enter stationary phase. During the prolonged stationary phase decreased amounts of MutS contributed to the increased mutagenesis resulting in mutator phenotype. The aim of our investigation was to analyze the mixed populations of E. coli K12 and S. enterica serovar Typhimurium during the prolonged period of carbon starvation due to the evaluation of the GASP phenomenon and its dependents of mutS gene. The mixture of one-day-old culture of S. enterica and ten-day-old cells of E. coli as minority showed the GASP phenomenon when they are resistant to a growth inhibitor (nalidixic acid or streptomycin). The same results were obtained when the mixture consisted of S. enterica as a minority cells. On the other hand, in mixed population of mutS mutants of both bacteria, in various ratios and age, only abortive GASP phenotype was observed. In addition, in the cells with GASP phenotype the chromosomal rearrangements were determined by PFGE.

Escherichia coli; Salmonella enterica; mutS mutants; GASP phenotype

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