The acidic stress-induced lysis is mediated by StkP and CiaRH in Streptococcus pneumoniae

PIÑAS G; ALBARRACIN ORIO A; CORTES P; ECHENIQUE J

Mar del Plata

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2007

We have described that acidic stress triggers autolysis in S. pneumoniae and that this process is mediated by the response regulator ComE, through a quorum sensing (QS) independent pathway. This constitutes a novel function of ComE, since it has been implicated in the regulation of competence development at alkaline pH, through a QS mechanism. In the present work, we studied the contribution of CiaRH two-component system and the StkP serine/threonine kinase in the acidic stress-induced lysis (ASIL), since they can regulate the comCDE operon and are involved in resistance to several types of stress and lytic conditions. We observed that ciaR and ciaH mutants lysed more rapidly than wild type strain (wt). Double ciaR/comE or ciaH/comE mutants were as susceptible to ASIL as the ciaR or ciaH mutants, indicating that CiaRH protects cells from ASIL by a ComE-independent pathway. Analysis of the stkP mutant showed that ASIL was blocked, and a similar phenotype was observed in stkP/ciaR or stkP/ciaH mutants. To investigate whether StkP was involved in the ComE-mediated ASIL pathway, we constructed a stkP/cup3 mutant, since strain cup3 has high levels of comE transcripts and shows accelerated lysis. Interestingly, ASIL was also abolished in the stkP/cup3 mutant. We conclude that StkP is necessary for the induction of ASIL by participating in both ComE and CiaRH regulatory pathways