LOPEZ, R.*; WATSON, KJ; NISHIGUCHI, MK: Molecular Mechanisms for Host Specificity in the Sepiola-Vibrio Mutualism

The Hawaiian bobtail squid Euprymna scolopes (Cephalopoda: Sepiolidae) and its luminous bacterial symbiont, Vibrio fischeri, provides a novel system for studying the interactions and evolutionary development of animal/bacterial associations. Previous studies have indicated that strain specificity exists, where native Vibrio strains outcompete non-native strains during colonization of the squid light organ. Although this specificity can be demonstrated at the physiological level, little is known whether host-specificity may be used by native strains to facilitate light organ infection. In other bacterial models such as Escherichia coli and Pseudomonas aeruginosa, expression of protein adhesive factors aid in host specificity. We are using PCR to determine presence or absence of four different adhesion operons [pap (pyelonephritis-associated pili), afa (afimbrial adhesin), sfa (S-fimbriae adhesin), pil (type IV methylphenylalanine pilins)] within native and non-native symbiotic Vibrios and related free-living strains. Regions of the papC gene have been successfully amplified in several strains and phylogenetically analyzed to determine relatedness to other pathogenic bacteria. These adhesin related genes have been compared within and between symbiont competent Vibrios in order to perform site-directed mutagenesis of these potential adhesion gene(s) for the creation of non-native mutants that are able to infect squid light organs as efficiently as native strains.