Detection of purple sulfur bacteria in purple and non-purple dairy wastewaters

Purple sulfur bacteria (PSB) in livestock wastewaters use reduced sulfur compounds and simple volatile organics as growth factors. As a result, the presence of PSB in manure storage ponds or lagoons is often associated with reduced odors. In this study, our objectives were to use molecular- and culture-based techniques to evaluate the occurrence of PSB in eight dairy wastewater ponds and identify physiochemical properties that might cause blooms to occur. Community DNA was extracted from composited wastewater samples, then the PufM gene and a conservative sequence for Chromatiaceae were amplified. Analysis of the 16S rRNA genes from denaturing gradient gel electrophoresis (DGGE) bands indicated that all of the dairy wastewater ponds contained sequences that matched with Thiocapsa roseopersicina, with sequences from a few ponds also matching with Marichromatium sp., Thiolamprovum pedioforme, and Thiobaca trueperi. PufM sequences amplified from pure and enrichment cultures were most similar to T. roseopersicina, indicating that it may be the dominant PSB in all wastewaters investigated. Purple wastewater ponds were also found to have the highest salinity, nitrogen, total and volatile solids, and chemical oxygen demand, suggesting that these factors might enhance PSB blooms. While not all ponds were phototrophic as determined visually and via a carotenoid assay, PSB could be enriched from the wastewaters, thus finding methods to enhance their growth in non-purple ponds should be investigated further