Proposal Defense: Lauren Speare

A proposal defense from UNC Marine Sciences graduate student, Lauren Speare. Presented by the UNC at Chapel Hill Department of Marine Sciences. The location of this event will be in seminar room G201 on the ground floor of Murray Hall on UNC-CH campus in Chapel Hill, NC. This event will be held on Monday, April 1st at 2:00pm. This seminar will also be broadcast live to both UNC’s Institute of Marine Sciences room 222 and online via Zoom.

Seminar Title: Essential elements for prey selection and T6SS-killing in a host-mucus like environment

Abstract: Bacteria form important associations with eukaryotic hosts and can critically impact host health by performing critical services such as directing host development and defense against infection. Many host-associated bacteria encode an arsenal of interbacterial killing mechanisms that they use to compete for limited space within host tissue. One such mechanism is the type VI secretion system (T6SS), a widely distributed, contact-dependent killing mechanism that acts as a molecular syringe to deliver toxic effector proteins from an “inhibitor” cell into a “prey” cell, resulting in growth inhibition or cell death if the prey lacks the appropriate immunity protein. Recent work has revealed T6SS-encoding bacteria target specific prey populations for killing, however the mechanisms used to target prey warrant further investigation. Previous work using in vitro coincubation assays on agar surfaces has uncovered valuable information on T6SS structure and dynamics. However, these conditions do not accurately reflect the physical environment experienced by many host-associated microbes, which is often a highly viscous mucus matrix. This condition forces contact between inhibitor and prey cells, making it difficult to study factors facilitating cell-cell contact between competing genotypes. The goal of my dissertation work is to use the symbiosis established between the Euprymna scolopes squid and Vibrio fischeri bacteria to as a model system to study the molecular mechanisms driving prey choice and T6SS-killing under host-mucus like conditions. Using a new in vitro coincubation assay which mimics the high viscosity mucus-like environment experienced by V. fischeri during host colonization, I propose to comprehensively identify and characterize essential genes for prey selection and T6SS-killing using two complementary methods. First, I will use a systematic, targeted mutation approach to investigate the extent to which a putative lipoprotein encoded on the V. fischeri T6SS2 genomic island mediates inhibitor-prey contact. The second approach will use strains identified in a genome wide transposon mutagenesis screen to characterize essential elements for T6SS activity and identify factors encoded by prey cells that are targeted by inhibitor cells. These findings will provide a valuable and comprehensive model of T6SS activity, as well as critical knowledge of how inhibitor cells interact with and target prey populations for competition under broadly conserved host-mucus like conditions.