Bacillus as a Heterologous Platform for Peptide Drug Discovery

The rising incidence of resistance to current antibiotics has become one of the world’s leading health problems. Nationally, at least 2 million people are infected with antibiotic-resistant bacteria, and there are over 23,000 deaths each year from antibiotic resistant infections. Natural products are a rich source of novel compounds for antibiotic development that can help circumvent antibiotic resistance. Bacteria have already selectively developed these molecules for that very purpose. At subinhibitory concentrations, natural product antibiotics can cause developmental and physiological responses in bacteria. This research focuses on harnessing the biosynthetic potential of one bacterial genus, Bacillus, to discover new antibiotic natural products and understand the broader roles these compounds play in bacterial communication. We use a combination of coculture, fluorescent transcriptional reporter assays, and MALDI-TOF IMS to identify and characterize the thiocillins and the broader thiopeptide family as chemical signals that induce biofilm formation in Bacillus subtilis. Biofilm production is an important bacterial defense. We probe into the mechanism of this thiocillin signaling activity in relation to antibiosis. We further pursue an intensive bioinformatics analysis of genus Bacillus to measure its chemical diversity and better understand the role of its specialized metabolites. We uncovered the biosynthetic machinery for a set of highly-conserved compounds across the Bacillus genus that play either known or currently unknown roles in signaling and bacterial development within Bacilli. We ascribe a signaling role to the highly-conserved alkylpyrone biosynthesis pathway in Bacillus. Additionally, we identify a number of unique, weakly conserved natural product biosynthesis pathways scattered across all species. The unique pathways offer leads for identifying new, distinct natural products that could exhibit previously unknown biological activities. To access the new pathways we identify in our bioinformatics analysis, we develop a heterologous expression platform that would allow us to rapidly move entire biosynthetic pathways into the host organism, Bacillus subtilis. Using a Bacillus based platform allows for rapid cloning and expression of peptides, and circumvents many challenges in the field. We develop tools that will enable future efforts to discover, characterize, and modify natural product antibiotics in Bacillus subtilis.Doctor of Philosoph