A two-component system controls H2O2 production that affects intracellular survival of Streptococcus pneumoniae

Buenos Aires

Encuentro; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

SAIB

Streptococcus pneumoniae is a main bacterial pathogen thatusually colonizes the upper respiratory tract, but the transitionmechanism from colonization to invasion of epithelial cells is notyet completely understood. Previously, we described that intracellularsurvival and acidic stress-induced lysis are controlled by theComE response regulator, which also regulates competence development.Here, we demonstrated that a phosphomimetic formof ComE increased its DNA-binding affinity, while non-phosphorylatableComE mutant displayed a lower DNA affinity. By moleculardynamic simulation, we predicted that ComE phosphorylationinduces conformational changes in the DNA-binding domain of thisregulator. To identify the ComE-regulated genes under acidic conditions,we performed a comparative transcriptomic analysis betweenthe non-phosphorylatable (np) mutant and wild type (wt) forms ofComE. We detected a differential expression of 104 genes involvedin different cellular processes suggesting that this pathway inducesglobal changes in response to acidic stress. In the np mutant, therepression of spxB (which encodes for pyruvate oxidase) correlatedwith a decreased H2O2 production, whereas the overexpression ofmurN (which encodes for A peptidoglycan branched peptide synthesisprotein) correlated with an increased resistance to antibiotic-inducedlysis induced by cell wall antibiotics, with this phenotype beingcompatible with cell wall alterations. Furthermore, we found thatthe np mutant displayed a blocked acidic stress-induced lysis, whilethe acid tolerance response was augmented compared with wt. Wethink that these phenotypes might account for the increased survivalin pneumocytes of the np mutant. We propose that the ComEpathway controls the stress response, thus affecting the intracellularsurvival of S. pneumoniae in pneumocytes, one of the first barriersthat this pathogen must cross to establish an infection.