DESCRIPTION (provided by applicant): All organisms, from bacteria to humans, need to "recognize" where they are, and respond accordingly. A pathogen must sense its location in the infectious cycle, then produce factors necessary for that site while repressing synthesis of inappropriate factors. Thus, disruption of key regulatory pathways can inhibit a pathogen's ability to infect, indicating useful targets for developing novel antibiotics. In our studies of th Lyme disease bacterium, Borrelia burgdorferi, we discovered that regulation of a new DNA/RNA-binding protein named BpuR is required for mammalian infection. B. burgdorferi regulates production of BpuR, synthesizing it at low levels during mammalian infection processes, and at high levels during colonization of vector ticks. We genetically engineered B. burgdorferi to constitutively produce high levels of BpuR during murine infection, and found the mutant to be significantly impaired in its ability to colonize mice. Transcriptomic analyses (RNA-Seq) demonstrated that BpuR significantly affects expression of approximately 5% of B. burgdorferi operons, disturbing cellular levels of several known virulence factors and metabolic enzymes. We hypothesize that disruption of the processes controlling production of BpuR will significantly inhibit B. burgdorferi infection. The planned studies are designed to elucidate the mechanism by which B. burgdorferi controls expression of this critical regulatory factor, and determine how disrupting that mechanism impacts upon infection processes.