INVOLVEMENT OF pbpE IN THE OSMOADAPTATION OF Bacillus subtilis

MARIA MERCEDES PALOMINO; CARMEN SANCHEZ RIVAS; SANDRA RUZAL

Pinamar Buenos Aires Argentina

Congreso; XLI Reunion Anual de SAIB (Sociedad Argentina de Investigaci¨®n y Biologia Molecular); 2005

SAIB

  INVOLVEMENT OF pbpE IN THE OSMOADAPTATION OF Bacillus subtilis Palomino M. M, Sanchez Rivas C, Ruzal S. M. Dpto. Qu¨ªmica Biol¨®gica, FCEN-UBA. Argentina. E-mail: mpalomino@qb.fcen.uba.ar B. subtilis cultures submitted to an osmotic stress increased its cell wall. Its structure was essentially due to the activity of several penicillin binding proteins (PBP). PBP4* is an endopeptidase involved in the peptidoglycan (PG) synthesis, coded by the pbpE gene. pbpE-lacZ fusions were studied. The wild type strain showed an increased transcriptional activity during stationary phase (5X)  and an upper induction in a high salt medium (25X). In order to discriminate if this effect was due to the elevated osmolarity and/or to sporulation, cultures in sporulation repressed media were studied. The same level of induction was observed, discarding a sporulation effect. Moreover, the ¦¤pbpE strain was much more osmosensitive than the wild type strain. In addition, no defects in sporulation were observed in this mutant, suggesting that PBP4* might play a role in the osmotolerance only. Whole cells and walls from the wild type and ¦¤pbpE strains grown in low and high salt conditions were prepared and susceptibility to mutanolysin (a muropeptidase) studied. Whole cells obtained from high salt medium, showed an increased lytic sensitivity for both strains. Their purified cells-walls showed a higher resistance. Biochemical analysis of the PG, to examine the pentapeptide composition and the degree of crosslinking, were undertaken to study the role of PBP4* in high salt grown.