Timecourse analysis of photosynthetic microbial communities that degrade cellulose and fix nitrogen

Tuesday, 16 December 2014
Anna Knapp1, Radmer van der Heyde1, Michael Sheets1, Lin Zhang2,3, Yazhou Wang4, Xiao Liu4, Beth Slikas5, Linda A Amaral-Zettler5 and Jean Huang1, (1)Organization Not Listed, Washington, DC, United States, (2)Woods Hole Oceanographic Inst, Woods Hole, MA, United States, (3)Univ Massachusetts Lowell, Lowell, MA, United States, (4)University of Massachusetts Lowell, Lowell, MA, United States, (5)Marine Biological Lab, Woods Hole, MA, United States
Cellulose is an abundant polymer derived from plant matter and it is also a nitrogen poor resource. Nutrient cycling is carried out by microbial communities in nature, and bacteria that degrade cellulose must be able to obtain a source of fixed nitrogen for growth. We used light wavelength selection to enrich for a series of anoxygenic photosynthetic microbial communities from marine and freshwater environments that degrade cellulose and fix nitrogen. This research examines how the communities carry out these processes. We compare community composition and metabolite production measured using high performance liquid chromatography and gas chromatography over time of growth of the communities. A freshwater community grown at 590nm showed the highest metabolic rates. Acetate and propionate reached maximum concentration at around day 4 and hydrogen concentrations peaked at 5uM on day 6 at stationary phase. There was no methane production by this culture suggesting methanogens were not present or inactive. In contrast, methanogenesis was very active in another freshwater community grown at 760/940nm. This culture showed acetate and propionate accumulation and hydrogen gas concentrations that decreased over time as well suggesting that hydrogenotrophic methanogenesis was occurring. A similar trend was observed in a marine community grown at 470nm. This work can enable determination of factors important for efficient community nutrient cycling and understanding of community dynamics. Future work will be done to determine the roles of the individual species of bacteria within the communities and to investigate the potential of these communities in biofuel production.