Abstract
Complications arising from antibiotic-resistant bacteria are becoming a major issue in modern medicine. Members of drug-resistant Enterobacteriaceae spp. include opportunistic pathogens (e.g., Salmonella spp.) that are among the leading causes of morbidity and mortality worldwide, and outgrowth of these bacteria is considered a strong indicator of intestinal dysbiosis. Microcins (small antimicrobial peptides) produced by some gut commensals can potentially cure these conditions by inhibiting select enteric bacteria and have been proposed as a viable alternative to antibiotic treatment. To explore the applicability of microcins as clinically relevant molecules, I developed a genetically engineered proof-of-concept probiotic to inhibit Salmonella spp. via microcin H47 production, when in an environment with tetrathionate, a molecule produced in the mammalian inflamed gut during the course of a Salmonella infection. This plasmid-based E. coli probiotic revealed interesting contradictions within the microcin literature, leading to the necessity to purify and characterize microcin H47,which was done for the first time as a part of this work. Purified microcin H47 was utilized in minimum inhibitory concentration assays, demonstrating an unrealized broad spectrum of activity. The pipeline utilized for this overproduction was done in a modular fashion, allowing for the subsequent purification of a microcin only speculated to exist, known as microcinI47. Finally, these two microcins, both characterized as catechol microcins, were produced from an array of vectors towards the purpose of optimization for in vivo experimentation in mouse models of gastrointestinal colonization by antibiotic resistant enteric bacteria.