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

Abstract

Bacteria require Copper (Cu) as an essential trace element to support cell processes; however, excess Cu can intoxicate bacteria. Here, we characterize the cop operon in group B Streptococcus (GBS), and establish its role in evasion of Cu intoxication and the response to Cu stress on virulence. Growth of GBS mutants deficient in either the copA Cu exporter, or the copY response regulator, were severely compromised in Cu-stress conditions. GBS survival of Cu stress reflected a mechanism of CopY activation of the CopA efflux system. However, neither mutant was attenuated for intracellular survival in macrophages. Analysis of global transcriptional responses to Cu by RNA-sequencing revealed a stress signature encompassing homeostasis of multiple metals. Genes induced by Cu stress included putative metal transporters for manganese import, whereas a system for iron export was repressed. In addition, copA promoted the ability of GBS to colonize the blood, liver and spleen of mice following disseminated infection. Together, these findings show that GBS copA mediates resistance to Cu intoxication, via regulation by the Cu-sensing transcriptional repressor, copY. Cu stress responses in GBS reflect a mis-metallation transcriptional signature that heightens virulence and represents an important part of the bacteria's ability to survive in different environments.

Regulatory cross-talk supports resistance to Zn intoxication in Streptococcus

“…Comparing to WT in identical conditions, copY -GBS had elevated levels of Zn, Cu, Mn, Fe and Mg within its cells. This broad level of mis-management of intracellular metal homeostasis in copY -GBS is specific to Zn stress compared to Cu stress [20]. Thus, copY-mediated control of metal homeostasis in GBS extends beyond that of Cu, and enables the bacteria to manage the intracellular pools of multiple metals.…”

“…We recently defined the role of copY in regulating responses of GBS to Cu stress via control of copA [20], and sczA in regulating Zn stress via czcD [21]. Here, to examine cross-control of metal efflux pathways by non-cognate regulators, we compared the growth and metal stress resistance phenotypes of GBS mutants deficient in copY or sczA using defined in vitro conditions of either Cu stress (for sczA -) or Zn (for copY -) stress.…”

“…The copyright holder for this preprint (which this version posted July 26, 2021. ; https://doi.org/10.1101/2021.07. 26.453799 doi: bioRxiv preprint 5 repressing copA via CopY to drive Cu export from the cell [20], and by activating czcD via SczA to regulate intracellular Zn levels [21], respectively.…”

“…A system for Zn efflux uses a Zn-specific transcriptional response regulator, sczA, to control a Zn efflux transporter, encoded by czcD [15,19]. These two systems of copA-copY and czcD-sczA for Cu and Zn export, respectively, have recently been characterized in group B Streptococcus (GBS), which responds to excess Cu and Zn by de-repressing copA via CopY to drive Cu export from the cell [20], and by activating czcD via SczA to regulate intracellular Zn levels [21], respectively.…”

The copper resistome of group B Streptococcus reveals insight into the genetic basis of cellular survival during metal ion stress

“…Several systems additional to the cop operon based on efflux proteins, including P-type ATPases are also described, and these contribute to bacterial resistance to metal stress for several pathogens, as reviewed elsewhere (5). Streptococcus agalactiae, also known as group B 5 Streptococcus (GBS) is an opportunistic bacterial pathogen of humans and animals for which a discrete genetic system for cellular management of Cu homeostasis based on the cop operon was recently described (12). The GBS cop operon regulates Cu import and export by responding to excess Cu and derepressing copA via CopY to drive Cu export from the cell (12).…”