Effects of a Double Mutation sbmA tolC on the Physiology of Escherichia coli

VALLEJOS ALICIA, SOCIAS SERGIO BENJAMIN, SALOMÓN RAÚL A.

San Miguel de Tucumán

Congreso; Reunión Anual de la Sociedad Argentina de MIcrobiología; 2011

  E. coli inner-membrane protein SbmA transports the peptide antibiotics microcin B17, J25 and bleomycin to the cell cytoplasm. In addition, the outer membrane-protein TolC is an essential component of several efflux pumps in E coli. We have previously demonstrated that an E coli K12 double mutant sbmA tolC carrying a Tn10 transposon, which should confer high resistance totetracycline, is hypersusceptible to that antibiotic. Several studies of this double mutant showed that it presents a deficient growth in solid medium even in the absence of tetracycline, forming small colonies compared to the parental control strain MC4100. In addition, a sbmA tolC double mutant rapidly loses viability four to five days after entry in stationary phase at 37ºC. Curiously, this phenotype was not observed when the cultures were grown at 30ºC but was enhanced at 42ºC, suggesting that the growth temperature markedly affects the double mutant physiology. Interestingly, this death phenotype in stationary phase is reversed by a diffusible peptide factor, which is present in the stationaryphase supernatants from liquid cultures of laboratory strains of E. coli K-12. Ours present efforts are aimed at clarifying the mechanism by which the high temperature affects the ability of the double mutant to form colonies, as well as purifying and characterizing the putative E. coli quorum sensing factor.