RNA Helicase Mediates Competitive Fitness of <i>Listeria monocytogenes</i> on the Surface of Cantaloupe
2018
Robert Price | Cameron Parsons | Sophia Kathariou
<i>Listeria monocytogenes</i> is a foodborne pathogen that is implicated in numerous outbreaks of disease (listeriosis) via fresh produce. The genetic features of <i>L. monocytogenes</i> that allow adherence and growth on produce remain largely uncharacterized. In this study, two non-motile transposon mutants were characterized for attachment, growth, and survival on the surface of cantaloupe rind. One of the mutants, L1E4, harbored a single transposon insertion in a DEAD-box RNA helicase gene (<i>lmo0866</i> homolog), while the other, M1A5, harbored an insertion in a gene from a flagellum biosynthesis and chemotaxis gene cluster (<i>lmo0694</i> homolog). When inoculated alone, neither mutant was significantly impaired in growth or survival on the surface of cantaloupe at either 25 or 37 °C. However, when co-inoculated with the wildtype parental strain, the RNA helicase mutant L1E4 had a clear competitive disadvantage, while the relative fitness of M1A5 was not noticeably impacted. Genetic complementation of L1E4 with the intact RNA helicase gene restored relative fitness on cantaloupe. The findings suggest that the DEAD-box RNA helicase encoded by the <i>lmo0866</i> homolog is critical for relative fitness of <i>L. monocytogenes</i> on cantaloupe. Mutant L1E4 was pleiotropic, being not only non-motile but also cold-sensitive and with reduced hemolytic activity, warranting further studies to elucidate the role of this helicase in the competitive fitness of <i>L. monocytogenes</i> on produce.
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