engleski

The Competition of mutS with mutT or recA Deficient Strains of Bacteria Escherichia coli and Salmonella enterica serovar Typhimurium during Prolonged Stationary Phase

Cells with mutations that deleteriously affect the fidelity of DNA replication or repair and cause an increase in the basic mutation frequency are called mutators. Numerous mutators generate a range of errors on different levels and types of effects. Three examples are mutT, mutS, and recA mutations that increase mutation frequency l000-l0000, l00, and 10-20 times, respectively. During prolonged starvation stress expressions the “ growth advantage in stationary phase” (GASP) phenotype expresses that depends on the appearance of new mutations in the population of E. coli. Three known GASP mutants, two in the global gene regulators, rpoS and lrp, and the third in sgaA gene as the result of genomic rearrangement, confer the ability of an old minority population to grow and invade a young majority population during prolonged stationary phase. The purpose of our investigation was to analyze the mixed populations of E. coli and S. enterica during the prolonged period of carbon starvation due to the evaluation of the GASP phenomenon and its dependents of functional mutS, mutT, and recA genes. In a typical GASP competition experiment, cells from a 10-day-old culture are inoculated as a numerical minority (1:10 vol/vol) into a young (1-day-old) culture. The mutant strains carry unique antibiotic resistance markers allowing each to be distinguished. When cultured under standard laboratory conditions in M9 medium, null mutations of each of the cells have no observable effect on cellular growth. Individually cultured mutant cells show similar cell yields after overnight growth and the same stationary-phase survival patterns as the wild-type. It has been observed that the mutant cells grow better in mixed populations than as monocultures. Ten-day-old mutT – bacterial cells of E. coli outgrow the young culture of mutS mutant on the second day and they show a strong GASP phenotype. After the third day, 10-day-old recA mutant of E. coli dominate the young mutS – cells of S. enterica although at the beginning the latter were in majority. Studying mutator cells in mixed bacterial cultures during prolonged starvation enables a new insight into their coexistence and interaction.

growth advantage in stationary phase; Escherichia coli; Salmonella enterica; recA gene; mutS gene; mutT gene

nije evidentirano