Project description:Comparison of the Streptococcus pneumoniae D39 spxB- mutant vs D39. For DNA microarray analysis, D39 wild-type and two independently obtained D39spxB- mutants were grown as four, two and two biological replicates, respectively, in Glc-M17 under semi-aerobic conditions and harvested at an OD595 of approximately 0.25 (mid-exponential). The RNA of both D39spxB- strains was compared to D39 and the combined data was analyzed. All other procedures regarding microarray analyses were done as described before. A gene was considered differentially expressed when the fold change was ≥ 2, ≤ 0.5, with a Bayes p ≤ 0.00001 and when at least 7 measurements were available.
Project description:The catalase-negative, facultative anaerobe Streptococcus pneumoniae D39 is naturally resistant to hydrogen peroxide (H2O2) produced endogenously by pyruvate oxidase (SpxB). Here, we investigate the adaptive response to endogenously produced H2O2. We show that lactate oxidase, which converts lactate to pyruvate, positively impacts pyruvate flux through SpxB and that ∆lctO mutants produce significantly lower H2O2. In addition, both the SpxB and pyruvate dehydrogenase complex (PDHC) pathways contribute to acetyl-CoA production during aerobic growth, and the pyruvate format lyase (PFL) pathway is the major acetyl-CoA pathway during anaerobic growth. Microarray analysis of the D39 strain cultured under aerobic vs. strict anaerobic conditions show up-regulation of spxB, a rhodanese-like protein (spd0091), tpxD, sodA, piuB, piuD and an Fe-S protein biogenesis operon under H2O2-producing conditions. Proteome profiling of H2O2-induced sulfenylation reveals that sulfenylation levels correlate with cellular H2O2 production, with endogenous sulfenylation of ≈50 proteins. Deletion of tpxD increases cellular sulfenylation 5-fold and has an inhibitory effect on ATP generation. Two major targets of protein sulfenylation are glyceraldehyde-3-phosphate dehydrogenase (GapA) and SpxB itself, but also include pyruvate kinase, LctO, AdhE and acetate kinase (AckA). Sulfenylation of GapA is inhibitory, while the effect on SpxB activity is negligible, consistent with this cell-abundant protein functioning as a “sink” for endogenous H2O2. Strikingly, four enzymes of capsular polysaccharide biosynthesis are sulfenylated, as are enzymes associated nucleotide biosynthesis via ribulose-5-phosphate. We propose that LctO/SpxB-generated H2O2 functions as a signaling molecule to down-regulate capsule production and drive altered flux through sugar utilization pathways.
Project description:Comparison of the Streptococcus pneumoniae D39 spxB- mutant vs D39. For DNA microarray analysis, D39 wild-type and two independently obtained D39spxB- mutants were grown as four, two and two biological replicates, respectively, in Glc-M17 under semi-aerobic conditions and harvested at an OD595 of approximately 0.25 (mid-exponential). The RNA of both D39spxB- strains was compared to D39 and the combined data was analyzed. All other procedures regarding microarray analyses were done as described before. A gene was considered differentially expressed when the fold change was M-bM-^IM-% 2, M-bM-^IM-$ 0.5, with a Bayes p M-bM-^IM-$ 0.00001 and when at least 7 measurements were available. One condition design comparision of two strains including a dye swap.
