Central role of manganese in regulation of stress responses, physiology, and metabolism in Streptococcus pneumoniae

The importance of Mn²⁺ for pneumococcal physiology and virulence has been studied extensively. However, the specific cellular role(s) for which Mn²⁺ is required are yet to be fully elucidated. Here, we analyzed the effect of Mn²⁺ limitation on the transcriptome and proteome of Streptococcus pneumoniae D39. This was carried out by comparing a deletion mutant lacking the solute binding protein of the high-affinity Mn²⁺ transporter, pneumococcal surface antigen A (PsaA), with its isogenic wild-type counterpart. We provide clear evidence for the Mn²⁺-dependent regulation of the expression of oxidative-stress-response enzymes SpxB and Mn²⁺-SodA and virulence-associated genes pcpA and prtA. We also demonstrate the upregulation of at least one oxidative- and nitrosative-stress- response gene cluster, comprising adhC, nmlR, and czcD, in response to Mn ²⁺ stress. A significant increase in 6-phosphogluconate dehydrogenase activity in the psaA mutant grown under Mn²⁺-replete conditions and upregulation of an oligopeptide ABC permease (AppDCBA) were also observed. Together, the results of transcriptomic and proteomic analyses provided evidence for Mn²⁺ having a central role in activating or stimulating enzymes involved in central carbon and general metabolism. Our results also highlight the importance of high-affinity Mn²⁺ transport by PsaA in pneumococcal competence, physiology, and metabolism and elucidate mechanisms underlying the response to Mn²⁺ stress.