characterization of microorganisms in dairy wastewater storage ponds

Dairy wastewaters from storage ponds are commonly land applied to irrigate silage crops. Given that diverse microbial populations are associated with cattle feces, the objective of this study was to use a culture-independent approach to characterize Bacteria and Archaea in dairy wastewaters. Using domain-specific primers, a region of the 16S rRNA gene was amplified from pooled DNA extracts from 30 dairy wastewaters and subsequently used to create a clone library. A total of 152 bacterial clones were examined and sequence matches were affiliated with the following groups: Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, and Synergistetes. Firmicutes was identified as the largest phylum representing up to 69% of the clone sequences. Of 167 clones representing Archaea, 7 genera were found to be closely related (91–100% sequence similarity) to isolates obtained from sediments and feces. Most of the putative sequence matches (98%) represented members from the class Methanomicrobia. With respect to the archaeal clones, only one of the putative sequence matches was affiliated with a methanogenic bacterium known to inhabit the rumen. Our results suggest that the dairy wastewater ponds do not support populations of methanogenic bacteria normally found in the cattle rumen.