Numerous symbiotic associations between chemotrophic bacteria and marine bivalves have been identified over the last three decades. Most are associations with thiotrophic (sulfur-oxidizing) bacteria, but methanotrophic (methane-oxidizing) and dual symbiosis of thiotrophic and methanotrophic bacteria have also been reported from deep-water bivalves. This laboratory has recently found bacterial endosymbionts in lucinid bivalves from shallow seagrass beds of Florida and the Bahamas that indicate a dual system in Phacoides pectinatus hosts. This project will take advantage of the availability of these bivalves to (1) resolve the phylogeny of genes associated with thiotrophic and methanotrophic bacterial metabolism from P. pectinatus hosts, and (2) use this genomic information to develop a combination of fluorescence in situ hybridization (FISH) technologies, microautoradiography and secondary ion mass spectroscopy to assess endosymbiont abundance and sulfide and methane utilization in the same animals. The multidisciplinary findings will not only provide insight into this novel bivalve symbiosis, but will have the potential to transform the field of symbiosis biology. Because lucinids substantially impact the productivity and diversity of seagrass beds and other nearshore marine environments, with abundances of up to 1500 individuals/m2, this research will improve understanding of methane cycling in climatically sensitive, nearshore marine systems, and should have broad implications for coastal resource management decisions in threatened coastal settings. The research will directly contribute to an enriching research and educational opportunity for women and minority students that are underrepresented in STEM areas. The findings will be used to develop online grade-appropriate science-education modules on 'animal-bacterial partnerships' for the K-12 science-education community.
