PARENT SESSION
Symposium 13: Interdisciplinary Challenges in the Biogeosciences
Organized by: L Hedin and R Jackson
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Oglethorpe Auditorium.
Microbial diversity in functional guilds: Does diversity matter in ecosystem function?
Ward, Bess*,1, Jackson, George2, 1 Princeton University, Princeton, NJ2 Texas A&M University, College Station, TX
ABSTRACT- Complex biogeochemical cycles, such as the microbially mediated nitrogen cycle, are deceptively simple when viewed in terms of the net chemical transformations they include. For example, the oxidation of ammonium to nitrite or the denitrification of nitrate to N2, can be determined from the net nitrogen fluxes measured using geochemical methods. Every biologically mediated process in a particular environment can be ascribed to the activity of an enzyme, encoded by a functional gene (e.g., ammonia monooxygenase, amoA, or nitrite reductase, nirS). Sequence analysis of such genes from the environment reveals a vast diversity within functional guilds; many different variants or alleles of the same functional genes are seen to be associated with each biogeochemical transformation. We are investigating the extent to which this genetic diversity is important in determining or regulating the overall rates of biogeochemical processes. In order to compare diversity/function relationships among sites and times, it is necessary to assess the degree to which the total diversity of the environment has been sampled. The results of our comprehensive diversity analysis of genes involved in nitrification and denitrification have been used to assess the shape of the 'species' abundance curve for functional genes. While the range of sequence diversity varies significantly between genes (e.g., amoA vs. nirS), their abundances appear to be lognormally distributed and should allow us to assess the main features of the community composition in relation to environmental variables and function. The initial development of DNA microarrays used to evaluate the microbial assemblage along a gradient of measured biogeochemical transformation rates within Chesapeake Bay will be presented.
Key words: ecosystem function, microbial diversity, DNA microarrays