Programmed cell death in Streptococcus pneumoniae is induced by acidic stress and regulated by quorum sensing.

PIÑAS GE; CORTES PR; ECHENIQUE J

Bariloche

Congreso; XXXIX Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2003

SAIB

In bacteria, programmed cell death mainly lead to cellular lysis, and plays an important role in certain developmental process. In S. pneumoniae, lysis is produced by the major autolysin LytA. Our studies on acid tolerance response (Cortes et al., poster presentation) showed that log-phase cells lysed when cultured at pH 5.6 after 3 Hs of incubation at 37oC. With the aim to understand the mechanism of acid-induced autolysis, we analysed mutants with an altered lytic phenotype. Previously, we have described a serine threonine kinase, StkP, whose mutant stkP::km showed autolysis in log-phase and to be essential for competence development activating comCDE transcription (Echenique et al., in revision). We analysed the impact of stkP::km mutant in acidinduced autolysis, and it showed early autolysis compared with wild-type. Considering that comCDE transcription is not activated in the stkP::km mutant, we expected that comE::km mutant should present the same phenotype. Interestingly, this mutant presented no lysis at pH 5.6, however ciaR::spc, a response regulator mutant that present hyper-expression of comCDE, lysed as early as stkP::km. These results allow us to conclude that programmed cell death is induced by an environmental condition like low pH, and it?s controlled by a quorum sensing mechanism as ComCDE. We also propose that StkP had a protector role against acid-induced autolysis, independently of ComCDE pathway.