The mutualistic association between sepiolid squids (Mollusca: Cephalopoda) and their Vibrio symbionts is an experimentally tractable model to study the evolution of animal and bacterial associations at various levels of interaction (genetics, physiology, population ecology). Since symbiotic bacteria are environmentally transmitted to new hosts with every generation, it provides an opportunity to resolve how the ecology of the free-living symbiont affects the architecture of bacterial-host interactions. Bacteria encounter potentially conflicting selective pressures, competing with one another to colonize and persist in the sepiolid light organ, but also competing for scarce resources in the environment outside the squid. A hierarchy of colonization exists, where particular V. fischeri strains out-compete other V. fischeri strains for colonization of their native squid partner, and abiotic factors such as water and temperature can affect the fitness of different strains. Genetic factors that contribute to intra-strain variations in fitness have not been elucidated, and neither have the genetic factors that likely contribute to intra-strain fitness in the environment. The following project will examine how genes that are highly-expressed exclusively in sea water or expressed exclusively in the light organ contribute to bacterial fitness. The present proposal is an extension of the current work in my laboratory, and focuses on four specific goals: i) Characterize environmentally-relevant phenotypes of strains with null mutations in highly-expressed, variable genes. ii) Determine whether a mutant strain complemented with the wild-type operon from the same strain is fit for environmental persistence (free-living) than the same strain complemented with the operon from a different strain. iii) Examine whether symbiotic strains with specific variable loci complemented with the wild-type operon or gene from the same strain are fit for host colonization than the same strain complemented with the operon/gene from a different strain. iv) Measure whether symbiotic genes are found in pathogenicity islands through whole genome comparisons, and demonstrate positive selection of these genes compared to normal housekeeping genes.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Enhancement Award (SC1)
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Special Emphasis Panel (ZGM1-MBRS-2 (MV))
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Hall, Robert H
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New Mexico State University Las Cruces
Schools of Arts and Sciences
Las Cruces
United States
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Chavez-Dozal, Alba; Gorman, Clayton; Nishiguchi, Michele K (2015) Proteomic and metabolomic profiles demonstrate variation among free-living and symbiotic vibrio fischeri biofilms. BMC Microbiol 15:226
Chavez-Dozal, Alba A; Gorman, Clayton; Lostroh, C Phoebe et al. (2014) Gene-swapping mediates host specificity among symbiotic bacteria in a beneficial symbiosis. PLoS One 9:e101691
Soto, William; Rivera, Ferdinand M; Nishiguchi, Michele K (2014) Ecological diversification of Vibrio fischeri serially passaged for 500 generations in novel squid host Euprymna tasmanica. Microb Ecol 67:700-21
Soto, William; Nishiguchi, Michele K (2014) Microbial experimental evolution as a novel research approach in the Vibrionaceae and squid-Vibrio symbiosis. Front Microbiol 5:593
Chavez-Dozal, Alba; Gorman, Clayton; Erken, Martina et al. (2013) Predation response of Vibrio fischeri biofilms to bacterivorus protists. Appl Environ Microbiol 79:553-8
Guerrero-Ferreira, Ricardo; Gorman, Clayton; Chavez, Alba A et al. (2013) Characterization of the bacterial diversity in Indo-West Pacific loliginid and sepiolid squid light organs. Microb Ecol 65:214-26
Chavez-Dozal, Alba; Hogan, David; Gorman, Clayton et al. (2012) Multiple Vibrio fischeri genes are involved in biofilm formation and host colonization. FEMS Microbiol Ecol 81:562-73
Soto, W; Punke, E B; Nishiguchi, M K (2012) Evolutionary perspectives in a mutualism of sepiolid squid and bioluminescent bacteria: combined usage of microbial experimental evolution and temporal population genetics. Evolution 66:1308-21
Zamborsky, D J; Nishiguchi, M K (2011) Phylogeographical patterns among Mediterranean sepiolid squids and their Vibrio symbionts: environment drives specificity among sympatric species. Appl Environ Microbiol 77:642-9
Chavez-Dozal, Alba; Nishiguchi, Michele K (2011) Variation in biofilm formation among symbiotic and free-living strains of Vibrio fischeri. J Basic Microbiol 51:452-8

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