Location: Bioenergy Research Unit
Title: Quantitative real-time PCR analyses of sulfate-reducing bacteria in swine manure and the inhibitory effects of condensed tannins Authors
Submitted to: Microbial Ecology International Symposium
Publication Type: Abstract Only
Publication Acceptance Date: August 22, 2008
Publication Date: N/A
Technical Abstract: Odorous chemicals produced by anaerobic bacteria in stored swine manure are a nuisance and potential health hazard. One of the more odorous compounds is hydrogen sulfide (H2S), produced primarily by sulfate-reducing bacteria (SRB). However, little is known about these bacteria in stored swine manure. A quantitative real-time PCR approach was developed to target and quantify the SRB population in manure. This assay specifically targeted the conserved dsrA gene of SRB, which encodes a key enzyme involved in sulfate respiration and production of H2S. Degenerate primer sets amplifying dsrA genes were used to detect three different groups of SRB, and the products were quantified using SYBR Green. Sequenced clones isolated from swine manure were most similar to Desulfovibrio sp. and Desulfobulbus sp., and it was discovered that the populations of these SRB differed within different manure ecosystems. This approach was then applied to study the effect of condensed tannins on SRB populations and the production of H2S in swine manure. Swine manure was treated with and without 0.5% w/v condensed tannins and incubated anaerobically for 28 days. H2S production was measured with a gas analyzer, and aliquots of manure were removed periodically for qRT-PCR of the different populations of SRB. Addition of condensed tannins reduced the numbers of Desulfobulbus-like Group 1 SRB by 96%, and this reduction correlated with a 98% reduction in H2S production over the course of the study. This research demonstrates that condensed tannins can suppress H2S production and reduce levels of SRB in swine manure.