Cellular management of Zinc in group BStreptococcussupports bacterial resistance against metal intoxication and promotes disseminated infection

Abstract

Zinc (Zn) is an essential trace element for normal bacterial physiology but divergently, can intoxicate bacteria at high concentrations. Here, we define the molecular systems for Zn detoxification in Streptococcus agalactiae, also known as group B Streptococcus, and examine the effects of resistance to Zn stress on virulence. We compared the growth of wild-type bacteria and mutants deleted for the Zn exporter, czcD, and response regulator, sczA, using Zn-stress conditions in vitro. Macrophage antibiotic protection assays, and a mouse model of disseminated infection were used to assess virulence. Bacterial responses to Zn stress were defined by RNA-sequencing and qRTPCR. czcD and sczA enabled S. agalactiae to survive Zn stress, with the putative CzcD efflux system activated by SczA. Additional genes activated in response to Zn stress encompassed divalent cation transporters that contribute to regulation of Mn and Fe homeostasis. In vivo, the czcD-sczA Zn-management axis supported virulence in the blood, heart, liver and bladder. Additionally, several genes not previously linked to Zn stress in any bacterium, including, most notably, arcA for arginine deamination, were shown to mediate resistance to Zn stress; representing a novel molecular mechanism of bacterial resistance to Zn stress. Thus, S. agalactiae responses to Zn stress are controlled by sczA which regulates czcD, with additional mechanisms of resistance to Zn stress supported by arcA, encoding arginine deaminase. Management of Zn stress in S. agalactiae is important for virulence and bacterial survival in the host in the context of systemic infection.

Copper intoxication in group BStreptococcustriggers transcriptional activation of thecopoperon that contributes to enhanced virulence during acute infection

“…This may provide context for elevated mntH2 expression in the presence of modest Cu stress in our study, since Cu-bound MntR has a much lower affinity for binding its target operator sequence (14580210). We also note that mtsABC and mntH2 are also up-regulated in concert with down-regulation of Fe-transporting fetAB in response to Zn stress in GBS (49). Together, our data indicate that modulation of mtsABC, mntH2 and fetAB expression forms parts of a transcriptional signature of GBS exposed to Cu or Zn stress.…”