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Abstract
D-amino acids are ubiquitous in nature and their function in microorganisms is an ongoing areas of interest. In bacteria, D-Glu and D-Ala are associated with peptidoglycan cell wall, while other non-canonical D-amino acids (NCDAAs) are implicated in a variety of processes. Vibrio cholerae’s broad-spectrum racemase, BsrV, produces NCDAAs that affect peptidoglycan structure and strength in stationary phase. Orthologs of BsrV are found in several members of the Vibrionaceae, and I investigated the role of BsrV in Vibrio fischeri. A V. fischeri bsrV mutant had reduced D-amino acid production, attenuated growth in low-salt media, and subtly altered peptidoglycan structure. The bsrV mutant was unaffected in its symbiosis with Euprymna scolopes but out-competed the wild type when cultured in a high-salt medium, revealing a fitness cost to harboring bsrV. This study illustrates distinct functions for BsrV between similar organisms and provides a foundation for additional research on BsrV-produced D-amino acids.