Detection of Purple Sulfur Bacteria in Purple and Non-purple Dairy Wastewaters.

The presence of purple bacteria in manure storage lagoons is often associated with reduced odors. In this study, our objectives were to determine the occurrence of purple sulfur bacteria (PSB) in seven dairy wastewater lagoons and to identify possible linkages between wastewater properties and purple blooms. Community DNA was extracted from composited wastewater samples, and a conservative 16S rRNA gene sequence within and genes found in both purple sulfur and nonsulfur bacteria was amplified. Analysis of the genes indicated that all of the lagoons contained sequences that were 92 to 97% similar with . Sequences from a few lagoons were also found to be similar with other PSB, such as sp. (97%), (93-100%), and (95-98%). sequences amplified from enrichment and pure cultures were most similar to (93-96%). Carotenoid pigment concentrations, which were used as an indirect measure of purple bacteria levels in the wastewaters, were found to be positively correlated with salinity, nitrogen, total and volatile solids, and chemical oxygen demand; however, salinity could be the dominant factor influencing purple blooms. Due to the detection of PSB sequences in all lagoons, our findings suggest that the non-purple lagoons may have been purple in the past or may have the potential to become purple in the future.