Examination of the Cop Operon Repressor and the Effects of Copper and Zinc in Streptococcus pneumoniae

Abstract

Streptococcus pneumoniae is a Gram-positive opportunistic pathogen that typically lives asymptomatically in the human nasopharynx but can cause pneumoniae, meningitis, otitis media, and sepsis. As with any organism living within a host, S. pneumoniae must acquire all its nutrients from the host. One group of essential nutrients is metals. Metals are vital to many cellular processes where they serve as structural components or catalytic cofactors of proteins. While metals are essential for life, they can also become toxic if their concentration is not tightly regulated. Bombardment of bacteria with toxic metals is one of the strategies of the mammalian innate immune system. Two metals that are known for their antimicrobial activity are copper and zinc. The metal environment will change as the bacteria move to different host tissues or experience the host immune response. In order to overcome stresses imposed by excess metal, bacteria encode metal efflux proteins. A notable example is the cop operon, a dedicated copper export system under the control of CopY. CopY is a metal-sensitive repressor that binds more tightly to DNA in a zinc-bound state and releases from DNA upon copper binding. Due to the role of these two metals in CopY regulation and their use as antimicrobials, we studied how changes in their concentrations impact S. pneumoniae. This dissertation explores the transcriptional and metabolic profile under a range of zinc and copper concentrations. In addition, we focused on CopY as we had predicted its regulon would likely expand beyond the cop operon. However, this was not the case, and we now propose an updated consensus operator sequence for CopY. Lastly, we look at how dysregulation of the cop operon affects the cell and we present the early stages of work to predict the CopY regulon across bacteria for which a full annotated genome is available.