1st Place: Screening a novel symbiont-mediated antibacterial mechanism from the termite gut

The eastern subterranean termite, Reticulitermes flavipes, is a valuable model to study symbiotic functions that help provide defense against invading microbes. The symbionts of termites have been associated with digestion, pathogen protection, and mediating other host physiologies. Recently, our lab discovered the presence of a type VI secretion system (T6SS) in a native isolate from the termite gut (Serratia sp.). T6SSs are molecular machines embedded in the cell wall of some bacteria that target nearby cells. Upon contact, the T6SS delivers effector proteins, like toxins and cell manipulators, into the target cell resulting in cell death. Preliminary data in our lab suggests that symbionts with this secretion system outcompete one termite pathogen, Serratia marcescens, in vitro. We hypothesize that the type VI secretion system found in gut-associated Serratia is necessary for R. flavipes to outcompete opportunistic bacterial pathogen, Serratia marcescens, in vitro. To test this hypothesis, we plan to target and study one of the main structural components of the T6SS, the hcp gene, using site-directed mutagenesis. Then, we will repeat our co-culture competitions assays to determine if the T6SS is necessary to outcompete the termite pathogen in vitro. These assays will be analyzed using a chi-square test with the null hypothesis that Serratia isolates and the termite pathogen will grow in a 50:50 ratio.