engleski

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

Microbial populations, faced with environmental stress, respond by activating inducible systems or, alternatively, exploit genetic processes that can help select the cells better adapted to the new environment. A subpopulation of transient hypermutators could be a source of multiple variant alleles, providing a mechanism for rapid evolution under adverse conditions. The phenomenon of the outgrowing of the more capable mutants in batch bacterial culture is called growth advantage in stationary phase (GASP) phenotype. Mutations that deleteriously affect the fidelity of DNA replication or repair cause an increase in the basic mutation frequency are called mutators. There are a number of these mutations with different levels and types of effects. Two examples are mutT mutations that increase mutation frequency 1000-10000 times and mutS mutation which cause around 100 higher mutation frequencies and generate a range of error types. The purpose of our investigation was to analyze tha mixed populations of Escherichia coli K12 and Salmonella enterica serovar Typhimurium during the prolonged period of carbon starvation due to the evaluation of the GASP phenomenon and its dependents of mutS and mutT genes. The mixture of one-day-old culture of S. enterica and ten-days-old cells of E. coli as minority showed the GASP phenomenon when they were resistant to a growth inhibitor (nalidixic acid or streptomycin). The same results were obtained when the mixture consisted of S. enterica as minority cells. On the other hand, in mixed population of mutS mutants of both bacteria, of various ratios and age, only abortive GASP phenotype was observed. The capability of GASP mutants was not observed in the mixed cultures with mutT mutation of E. coli. In addition, in the cells from prolonged stationary phase the chromosomal rearrangements were determined by PFGE.

GASP phenomenon; E. coli; genetic rearrangement

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