MIP: Symbionts and Signaling: Quorum Sensing Among Sponge-Associated Bacteria

Indiana University, Bloomington IN

Investigators

Abstract

Marine sponges have proven to be a rich source for novel pharmaceuticals such as anticancer drugs and antibiotics. These simple animals also harbor a vast, yet stable population of symbiotic microorganisms that are often the source for the medicinally active compounds. In addition to generating useful metabolites for the host animal these microbes can also perform other important functions, including acquisition of limiting nutrients and protection against harmful disease agents. The microbial communities within sponges are complex and diverse, representing many different types of microbes with a great range of capabilities. As with most complex microbial communities, there is virtually no understanding of the factors and mechanisms that establish and stabilize the microbiota in sponges. For marine sponges, it is unclear how specific microbes are introduced and maintained in the face of the huge volume of microbe-containing seawater surrounding them, and how the appropriate balance of different microbes is fostered within the sponge tissue. One mechanism by which bacteria coordinate their activities is through the exchange of chemical signals. Over recent years it has become clear that many bacteria can "converse" through different chemical languages, and that this microbial conversation can have a major impact on microbial community function. In a related NSF Microbial Observatory project, a large group of sponge-associated microbes has been found to produce a specific family of communication signals called acyl-homoserine lactones (AHLs), known to regulate diverse processes including antibiotic synthesis, nutrient acquisition, and microbial gene exchange in other bacteria. AHLs are prime candidates for factors that shape the sponge community and facilitate coordination of microbial activities. This study will test the pervasiveness and importance of these signaling mechanisms for the well-characterized microbial communities of several shallow-water, tropical sponges. Advanced chemical, biochemical, molecular, microscopic and microbiological analyses will be applied to determine the extent to which these indigenous microorganisms communicate within the sponge, the functions under control of the signaling, and the connection to important attributes of the sponge, including production of novel metabolites. The study will provide broad insights into the ways that microbial communities proliferate and mature during host association, the regulation of microbial activity to promote symbiosis rather than disease, and the functional relationships between these microbes and the sponge. In a wider sense, this study will advance understanding of complex symbiotic processes and contribute to knowledge on signaling in interactions between bacteria and their hosts. This interdisciplinary project involves three different laboratories with different areas of expertise, and will train graduate students and postdoctoral researchers in ways that bridge the traditional areas of chemistry, ecology and molecular microbiology. Undergraduate student participation is also an important component of the study. In addition to undergraduate research assistants, the project also includes support for continuation of the successful Summer Microbiology and Research Training (SMaRT) course that offers a two week intensive laboratory research experience for minority students at the Center of Marine Biotechnology in Baltimore. This course provides students with a realistic research experience focused on sponge microbial communities, in close collaboration with the research scientists, postdoctoral researchers and graduate students.