PT - JOURNAL ARTICLE AU - Lauren Speare AU - Madison Woo AU - Anne K. Dunn AU - Alecia N. Septer TI - A large lipoprotein mediates target specificity for T6SS-dependent killing AID - 10.1101/2021.04.26.440508 DP - 2021 Jan 01 TA - bioRxiv PG - 2021.04.26.440508 4099 - http://biorxiv.org/content/early/2021/04/26/2021.04.26.440508.short 4100 - http://biorxiv.org/content/early/2021/04/26/2021.04.26.440508.full AB - Interbacterial competition is prevalent in host-associated microbiota, where it can shape community structure and function, impacting host health in both positive and negative ways. However, the factors that permit bacteria to discriminate among their various neighbors for targeted elimination of competitors remain elusive. We identified a specificity factor in Vibrio species that is used to target specific competitors for elimination. Here, we describe this specificity factor, which is associated with the broadly-distributed type VI secretion system (T6SS), by studying symbiotic Vibrio fischeri, which use the T6SS to compete for colonization sites in their squid host. We demonstrate that a large lipoprotein (TasL) allows V. fischeri cells to restrict T6SS-dependent killing to certain genotypes by selectively integrating competitor cells into aggregates while excluding other cell types. TasL is also required for T6SS-dependent competition within juvenile squid, indicating the adhesion factor is active in the host. Because TasL homologs are found in other host-associated bacterial species, this newly-described specificity factor has the potential to impact microbiome structure within diverse hosts.Competing Interest StatementThe authors have declared no competing interest.