Selection of host specific genes in environmentally transmitted mutualism

ARRA Awards to NMSU: Michele Nichiguchi

Agency: NIH/DHHS
PI: Michele Nishiguchi
Title: Selection of host specific genes in environmentally transmitted mutualism
Period: 9/1/2009-8/31/2011
Mutualistic associations between bobtail squids and their luminescent bacterial symbionts (genus Vibrio) make excellent models to study the evolution of animal-bacterial associations. Since symbiotic bacteria are transmitted through the surrounding seawater to new hosts with every generation, it provides a unique opportunity to resolve how the ecology of free-living bacteria effects the make-up of these squid-luminous bacterial partnerships, particularly with respect to factors such as genome evolution. Since Vibrio bacteria are quite easily adaptable to changing environmental conditions, this may lead to the possibility of range expansion of these bacteria to different squid populations, and may eventually lead to the evolution of new species of Vibrio. Using a bioinformatics approach, this supplemental proposal will examine changes that have occurred between symbiotic, free-living, and experimentally evolved Vibrio strains by comparing whole genomes and constructing networks based on the type of strain and the conditions as to how that strain was derived. The main hypothesis is to ascertain whether genes responsible for environmental success or those related to symbiotic competency (in either a native or non-native host) are important for the formation of a successful symbiosis, and if these genes or gene families are linked due to the nature of transmission (environmental). We will use an integrated bioinformatics approach, by combining genome sequencing, phylogenetic comparisons, and the formation of gene networks that integrate gene “hot spots” or areas under positive selection. Understanding beneficial microbes and their interactions with animals provides a foundation for determining the impact on the host, and whether evolved strains can become more infectious. This has direct applicability for approaching similar questions with other closely related pathogens (i.e., Vibrio cholerae, V. parahaemolyticus), and will lead to our understanding of how environmental reservoirs have become so important in the detection and diagnosis of pathogenic outbreaks.