THE ACID-INDUCED AUTOLYSIS IS COME-MEDIATED BY A QUORUM SENSING-INDEPENDENT PATHWAY IN PNEUMOCOCCUS

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

Rosario, Santa Fe. Argentina

Congreso; XLII Annual Meeting Argentine Society for Biochemistry and Molecular Biology (SAIB); 2006

Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB)

In pneumococcus, a quorum-sensing system controls the development competence at pH 7.8. The competence-stimulating peptide (CSP) is a cell-density signal secreted by an ABC transporter (ComAB), and its accumulation in the extracellular space is sensed by a transmembrane histidin kinase (ComD). Upon CSP-binding, ComD phosphorilates a response regulator (ComE), activating the transcription of the competence genes. We demonstrated that autolysis is triggered by acidic stress at pH 5.6 and mediated by ComE. However, competence is abolished at pH < 6.8, suggesting that ComE has another function in the acid-induced lysis. Here, we studied the connection between ComE and the quorum-sensing system under acidic conditions. To block the CSP circuit, we constructed the comA::km strain, which lysed at pH 5.6 as the wild-type strain (WT), but the lysis of the comA::ery/ comE::km mutant was inhibited, indicating ComE regulation by a quorum sensing independent pathway. To investigate the putative phosphorylation state of ComE at pH 5.6, we generated the hyperphosphorylating comDT233I mutant, which lysed more rapidly than WT, but the lysis of the ComDT233I/ comE::km mutant was not blocked at pH 5.6. These results suggest that ComE-P is necessary for the acid-induced lysis, but if ComE is absent, ComD could phosphorylate another protein (by a signal pathway known as ?crosstalk?) to induce lysis.