Protective action of ppgpp on microcin j25 sensitive trains by increase of yoji export activity

MARÍA FERNANDA POMARES; RICARDO FARÍAS; RAÚL SALOMÓN; PAULA VINCENT

Mar del Plata

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología molecular; 2007

Sociedad Argentina de Investigaciones en Bioquímica y Biología molecular

Many reports have shown that ppGpp has a significant role in growth rate control and gene expression during stationary phase. MccJ25-sensitive strains exhibit an increased resistance in stationary phase. These results led us to suppose that the accumulation of ppGpp could have a protective action against the MccJ25. In fact, colony counts dropped five orders of magnitude for AB1133 in the presence of MccJ25, while AB1133 transformed with a plasmid that overproduces ppGpp (pALS13) remained unaffected. Using AB1133 rpoS::Tn10, we demonstrated that sigma factor is involved in the protective effect of ppGpp since sensitivity of this strain harboring pALS13 was similar to the strain producing normal levels of ppGpp. MccJ25 had no effect either on transcription activity or on oxygen consumption (MccJ25 targets) in sensitive strains harboring pALS13. The fusion activity of yojI (a chromosomal E. coli transporter involved in MccJ25 exportation) was recorded in the absence and in the presence of pALS13. The results showed an increment of 100% in the yojI expression in the strain harboring pALS13. Using a biossay we demonstrated that the introduction of pALS13 plasmid increment the antibiotic secretion mediate by YojI. Our results suggest that the increment in ppGpp pool promotes YojI expression which in turn keeps the intracellular concentration of MccJ25 below a toxic level.