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Functional and Genetic Analysis of Microbial Communities in the Aerobic Rotational Membrane System Bioreactor.  J. Shimizu1, T. Rector2, M. Hummerick2, J. Garland2, and M. Roberts2. 1Colorado State University, Fort Collins, CO and 2Dynamac Corporation, Kennedy Space Center, FL.

    The Aerobic Rotational Membrane System (ARMS) is a reactor design under evaluation at the Kennedy Space Center for the biological treatment of urine, hygiene water, and humidity condensate in support of NASA Advanced Life Support Systems research. The proposed biological process involves coupled nitrification and denitrification in a single stage microgravity-compatible reactor where oxygen is provided to attached nitrification biofilms via hollow fiber aeration membranes. This report describes an evaluation of analytical microbiological methods for enumeration and community profiling of the ARMS reactor using the BD Oxygen Biosensor System (OBS) and Terminal Restriction Fragment Length Polymorphism (T-RFLP). The OBS assay, a method of community-level physiological profiling based upon fluorometric detection of oxygen consumption, was used to determine the functional response of heterotrophic and chemoautotrophic microorganisms (i.e., nitrifiers) in the reactor to defined resources.  Although the rate and extent of response in the OBS assay were found to be sensitive to resource concentration and inoculum density, nitrification activity was detected in membrane-attached biofilms. The T-RFLP assay, a method of community-level genetic profiling based upon PCR amplification of bacterial ribosomal DNA, was used to determine the genetic diversity and spatial heterogeneity of bacterial communities. Membrane-attached microbial communities were determined by T-RFLP profiling to share >80% similarity in replicate reactors. In combination, the OBS and T-RFLP methods enabled determination of spatial and temporal dynamics within microbial community function and structure in the ARMS reactor.