Effect of F0.F1-ATPase mutants on the acid-induced autolysis in pneumococcus.

PIÑAS GE; CORTES PR; ALBARRACIN ORIO AG; ECHENIQUE J

Cataratas Iguazu

Congreso; XL Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular,; 2004

SAIB

We have described that acidic stress in pneumococcus induced two different cellular processes. First, this pathogen induces an acid tolerance response (ATR), and after triggers a programmed cell death or autolysis. Recently, we also demonstrated the involvement of F0.F1-ATPase in the ATR mechanism by characterization of atp mutants (Cortes et al., poster presentation). This enzyme facilitates the extrusion of protons from the cell cytoplasm, preventing a drop in the intracellular pH in bacteria. With the purpose to evaluate the F0.F1-ATPase effect on acidinduced autolysis, wild-type cells were incubated at pH 7,6 with 10 μM DCCD, an specific inhibitor of this enzyme that blocks its H+-translocating activity. We found that DCCD-induced autolysis was similar to that one produced by acidic shock. To confirm the role of this enzyme in the acid-induced autolysis, two F0.F1-ATPase mutants were incubated at pH 5,6 and 37ºC for 6 hours. We observed that the atpC G47V strain, which showed an increased ATR, presented no lysis after 6 hours of incubation. On the contrary, the atpC V48L strain, which had a decreased ATR, showed an early induction of autolysis compared with the wild type strain. According to these data we conclude that functionality of the F0.F1- ATPase is required for preventing autolysis induced by acidic stress. Work is in progress to study the checkpoints by which pneumococcus, cultured under acidic conditions, pass from ATR to autolysis, or omit ATR producing directly autolysis.