Community Profiling: 16S rDNA Characterization of Bacteria on Halodule wrightii using PCR-DGGE and sequencing

Seagrasses are a major source of primary productivity in coastal aquatic ecosystems. But their global decline due to anthropogenic pressures is a concern.  Increased nutrients can increase abundances epiphytes on the leaves, phytoplankton and microorganisms in reducing the photosynthetic productivity of seagrasses by shading light and decreasing gas exchange.  We hypothesize that the microbial diversity of epiphytic biofilms will reflect and change with environmental conditions, thus serving as an indicator.  Bacterial epiphyte communities attached to seagrass Halodule wrightii at two sites (East Flats, Corpus Christi Bay and Nighthawk Bay, Upper Laguna Madre) were characterized by 16S rDNA sequenced diversity using PCR-DGGE (polymerase chain reaction denaturing gradient gel electrophoresis) and a clone library.  Group specific primers for alphaproteobacteria, gammaproteobacteria, cyanobacteria, and bacteroidetes were used for PCR-DGGE. Universal primers 341f and 907r were used for the clone library. DGGE profiles show differences in bacterial diversity and richness between sites.  DNA sequences were compared to BLAST and Ribosomal Database Project II to identify the types of microorganisms present.  Results indicate the presence of methanotrophs, nitrogen fixers, nitrifiers, sulfide oxidizers, and other species indicative of an interface between aerobic and anaerobic conditions. This type of data should be useful for determining epiphyte-seagrass dynamics.