Education

Ph.D. Scripps Institution of Oceanography, UCSD

Research interests

Research in my laboratory is centered on the physiology, ecology, and evolution of symbiotic associations between bacteria and marine bivalves. These include endosymbioses which allow hydrothermal vent and hydrocarbon seep bivalves to "eat" hydrogen sulfide and methane (natural gas), and endosymbioses which allow other bivalve species to survive on a diet composed entirely of wood. Molecular approaches are emphasized for examining questions of host-symbiont interactions from both physiological and evolutionary perspectives. Areas of investigation include host-symbiont recognition, coregulation, and coevolution, as well as the mechanisms and consequences of symbiont transmission.

Ongoing projects:

1) Investigation of host and symbiont co-speciation using comparative molecular phylogenetic analysis. Members of the bivalve families Mytilidae, Vesicomyidae, Solemyidae and the superfamily Lucinacea and their respective symbionts are currently under investigation. This project is geared toward elucidating the origins and evolution of these ancient symbiotic associations and assessing the effects of these symbioses on the evolution of the symbiotic partners. Current investigations involve comparative phylogenetic analysis of homologous genes and spacers of the rRNA operons in hosts and symbionts.

2) Investigation of the mechanisms of symbiont transfer and the mutual influence of the symbiotic partners on the development and physiological functions of the symbiosis. These investigations center on bacterial endosymbioses found in the wood boring clams of the families Teredinidae (shipworms) and Pholadidae (subfamily Xylopagainae). Among our goals are to determine the diversity that exists within these symbiont populations, to identify biomarker sequences specific for individual symbiont strains, and to track uptake and transmission of symbionts by using in situ hybridization techniques to detect and localize these specific biomarker sequences in the animal tissues and/or the surrounding environment.

3) We are using molecular and biochemical methods to isolate, identify, localize, and characterize genes and enzymes involved in digestion of wood by shipworms. Our goal is to elucidate the mechanism of cellulose degradation by shipworms and to describe the role of the symbionts and the hosts in this process.

It is clear that no organism grows in a vacuum. Virtually all animals have specific bacterial associates that profoundly influence their survival in both positive and negative ways. The symbioses described above provide fascinating model systems for examining the physiological ecology and evolution of specific animal bacterial associations.

Publications

• Organ. 2000 Sep 28;42(3):199-206.
• Evol. 2000 Apr;15(1):25-33.
• mussels take wooden steps to deep-sea vents? Nature. 2000 Feb
• 17;403(6771):725-6.
• and Synechococcus (Cyanobacteria). J Mol Evol. 1998 Feb;46(2):188-201.
• washingtona. Biol Bull. 1997 Apr;192(2):253-61.
• Proc Natl Acad Sci U S A. 1995 Oct 10;92(21):9598-602.

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