The role of metal ion homeostasis in regulating bacterial capsule production - Project Summary/Abstract Capsular polysaccharide (CPS) produced by pathogenic bacteria is a key virulence determinant for bacterial survival in the human host, but knowledge of how CPS production is regulated remains limited. Given the need for pathogenic bacteria to modulate CPS expression (thickness) among various host niches during disease progression, we postulate here that available environmental factors such as metal ion micronutrients can influence CPS production. The long-term goal is to help develop alternative metal-based antimicrobial therapeutics for clinical treatment of bacterial diseases in humans. The overall objectives in this application, which constitute the first step toward attainment of the long-term goal, are to identify the molecular mechanisms by which cellular metal ion ratios, specifically manganese (Mn), zinc (Zn), and calcium (Ca), influence CPS production, while increasing exposure of undergraduates to research and enhancing Idaho State University’s biomedical research enterprise. The central hypothesis is that metal ion micronutrients regulate CPS biogenesis via direct modulation of enzyme activity in pathogenic bacteria using Streptococcus pneumoniae (Spn) as a Gram-positive model bacterium. The rationale for this project is that a mechanistic understanding of how cellular metal ion ratios regulate CPS expression levels would provide new opportunities for the subsequent identification and development of targets for the design of novel interventions to treat human pathogenic bacterial infections. To attain the overall objectives, we will pursue the following specific aims: 1) Identify the mechanism(s) whereby bioavailable Mn/Zn ratios affect CPS production; and 2) Determine the role of Ca in Mn homeostasis and CPS biogenesis. The first aim will assess the physiological and biochemical impact of bioavailable Mn/Zn ratios on several Mn-utilizing enzymes involved in various arms of the Spn CPS biosynthetic pathway. The second aim will assess the impact of Ca/Mn ratios on the intracellular metal landscape and CPS biosynthesis in coordination with RNAseq and proteomic analysis. The overall approach combines classical microbiology techniques with modern day applications that span the interface of biology and chemistry, thereby exposing undergraduates to interdisciplinary research techniques. The research proposed in this application is innovative, in the applicant’s opinion, because it represents a substantive departure from the status quo by focusing on the impact of overall cellular metal ion micronutrient ratios and their capacity to regulate bacterial CPS biogenesis. The research proposed will also further the understanding of how cellular metal ion availability serve as signaling factors that influence global cellular changes and cellular programing during pathogenesis. The proposed research is significant because it is expected to provide a strong foundation for subsequent future design of mechanistic and alternative metal- based drug development strategies to combat human bacterial pathogens prone to exhibiting multidrug resistance.
