engleski

Moderate Growth Advantage in Stationary Phase (GASP) phenomenon of enterobacteria over Lactobacillus brevis L62 in mixed cultures

The ability of Escherichia coli to grow for a long period of time, over five years, during carbon starvation has been termed Growth Advantage in Stationary Phase (GASP) phenotype. This phenomenon has been observed in gram-negative and gram-positive bacteria. GASP phenomenon is due to various beneficial mutations in two global regulators of transcription of rpoS and/or lrp genes, as well as rearrangements involving IS5 insertion sequences. The purpose of our investigation was to analyze mixed populations of Lactobacillus brevis L62 and E. coli or Salmonella enterica serovar Typhimurium during the prolonged period of carbon starvation due to the evaluation of their interaction and GASP phenomenon. 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. According to previous analysis of the competition growth of E. coli, mutants can result in four GASP phenotypes, however we noticed a new phenotype that we named moderate. This new class is characterized by GASP mutants of enterobacteria which are capable of outgrowing the younger lactobacillus culture and than coexist together. From fifth to eleventh day of growth, cells in mixed culture of S. enterica and L. brevis showed firm coexistence in range of 109 and 108 CFU ml-1, respectively. Studying cell trait in mixed bacterial cultures during prolonged starvation gives us a new insight into their interaction and evolution.

Lactobacillus brevis; enterobacteria; moderate GASP phenomenon

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