Research Interests

Marine Microbiology and the Discovery of New Drugs

The major focus of research in my laboratory is the investigation of symbiotic bacteria associated with marine invertebrates, in particular, sponges. Many important compounds with pharmaceutical potential have been discovered in sponges and other invertebrates. In some cases, the compounds of interest are produced, not by the sponges themselves, but by bacteria associated with the sponges. We are identifying many of the bacteria present in sponges even if we cannot grow them, by cloning the genes encoding the 16S ribosomal RNA from these sponges. We can then rationally select culture conditions to be able to grow a higher proportion of the bacteria and, hopefully, find the ones that produce important compounds. We have isolated a Micromonospora sp. strain M42 from the Indonesian sponge Acanthostrongylophora that produces manzamine A, an antimalarial compound found in this sponge. We also succeeded in isolating symbiotic Vibrio sp. that produce kahalalide F, a promising anti-cancer compound first found in the Hawaiian mollusk Elysia rufescens. These projects are in collaboration with Dr. Mark Hamann at the School of Pharmacy, University of Mississippi.

We also have research projects in the important first stage of the drug discovery process, focusing on discovery of unusual marine bacteria that have a high potential of producing novel products. A major part of my research program is the study of actinomycetes from the marine environment. Actinomycetes are very important in terms of production of bioactive compounds, for example more that two-thirds of antibiotics come from this single group of bacteria. Actinomycetes are generally thought of as soil microbes. Soils from around the world have been searched by pharmaceutical companies for novel actinomycetes, but these searches are now resulting in rediscovery of previously investigated actinomycetes. However, we have been finding an interesting and diverse assemblage of novel actinomycetes in the marine environment.

The overall aim of this research is to improve knowledge of marine microbial ecology in order to more efficiently be able to isolate marine bacteria which produce important bioactive compounds that can be used as antibiotics and anti-cancer drugs.

Diversity and function of microbial symbionts

All forms of higher life involve interactions between eukaryotes and prokaryotes. Sponges are the most primitive multicellular eukaryotic organisms and provide an excellent model system for understanding evolution of complex symbiotic interactions. Microbial communities associated with marine sponges are remarkably diverse, include novel bacteria not found in other ecosystems and closely related sponges have similar microbial communities. We are studying the diversity and functions of these communities. We have succeeded in maintaining sponges in captivity for two years and have monitored shifts in the microbial communities in aquaculture. The role of symbiotic bacteria in nitrogen fixation is under investigation. Signaling compounds produced by sponge-associated bacteria are being investigated with our collaborator Dr. Clay Fuqua at Indiana University.