Characterization of an exclusion mechanism in an integrative and conjugative element in Bacillus subtilis

Abstract

Horizontal gene transfer is the acquisition of new genetic material that can confer novel phenotypes to bacteria and contribute to their evolution. Conjugation is an important mechanism of horizontal gene transfer that involves the direct transfer of DNA between two cells and is mediated by mobile genetic elements encoding type IV secretion systems. Conjugative elements prevent redundant transfer by a mechanism known as exclusion that inhibits their cognate secretion systems. Exclusion is prevalent among conjugative elements, suggesting it is advantageous and potentially essential. Yet very few exclusion mechanisms are characterized, and the advantages they provide are not well understood. My work characterizes the exclusion mechanism of an integrative and conjugative element found in a Gram-positive bacterium. In combination with several other studies, my results point to a potentially conserved mechanism and novel benefits of this phenomenon, furthering our understanding of how mobile genetic elements regulate their transfer, impact their bacterial hosts, and mediate horizontal gene transfer.