Dissertations & Theses (Open Access)

Date of Award

Spring 5-2019

Degree Name

Master of Science (MS)


Charles Darkoh, Ph.D

Second Advisor

Mary Ann Smith, Ph.D


The Accessory Gene Regulator (Agr) quorum sensing system is a cell-cell communication system that is involved in regulating various bacterial processes such as toxin production, antibiotic production, biofilm formation, and other biomolecules. Despite the importance of the Agr system to Clostridia, the similarity and diversity of the system have been overshadowed by phylum-wide investigations of individual Agr components. To determine the variability of the Agr system within and between Clostridium species, we compared the sequences of its components within and between species using bioinformatics and phylogenetic tools. Putative Agr operons were found in over 50 Clostridia species, including undescribed components in some of the species with known operons. The Agr components were mostly similar within species and in some cases, differed between other Clostridial species. Conserved residues of unknown function were also found. The prevalence of the Agr system and the identification of common motifs in its components opens up therapeutic targets to be harnessed for the development of non-antibiotic and anti-virulence therapies for pathogenic Clostridial infections.