Microbial sulfate reduction by Desulfovibrio is an important source of hydrogen sulfide from a large swine finishing facility.

There is still a lack of understanding of H2S formation in agricultural waste, which leads to poor odour prevention and control. Microbial sulfate reduction is a major process contributing to sulfide formation in natural and technogenic environments with high sulfate and low oxygen concentration. Agricultural waste can be considered a low-sulfate system with no obvious input of oxidised sulfur compounds. The purpose of this study was to characterise a microbial community participating in H2S production and estimate the microbial sulfate reduction rate (SRR) in manure slurry from a large-scale swine finishing facility in Western Siberia. In a series of manure slurry microcosms, we identified bacterial consortia by 16S rRNA gene profiling and metagenomic analysis and revealed that sulfate-reducing Desulfovibrio were key players responsible for H2S production. The SRR measured with radioactive sulfate in manure slurry was high and comprised 7.25 nmol S cm-3 day-1. Gypsum may be used as a solid-phase electron acceptor for sulfate reduction. Another plausible source of sulfate is a swine diet, which often contains supplements in the form of sulfates, including lysine sulfate. Low-sulfur diet, manure treatment with iron salts, and avoiding gypsum bedding are possible ways to mitigate H2S emissions from swine manure.

Thermophilic Chloroflexi Dominate in the Microbial Community Associated with Coal-Fire Gas Vents in the Kuznetsk Coal Basin, Russia.

Thermal ecosystems associated with areas of underground burning coal seams are rare and poorly understood in comparison with geothermal objects. We studied the microbial communities associated with gas vents from the coal-fire in the mining wastes in the Kemerovo region of the Russian Federation. The temperature of the ground heated by the hot coal gases and steam coming out to the surface was 58 °C. Analysis of the composition of microbial communities revealed the dominance of Ktedonobacteria (the phylum Chloroflexi), known to be capable of oxidizing hydrogen and carbon monoxide. Thermophilic hydrogenotrophic Firmicutes constituted a minor part of the community. Among the well-known thermophiles, members of the phyla Aquificae, Deinococcus-Thermus and Bacteroidetes were also found. In the upper ground layer, Acidobacteria, Verrucomicrobia, Actinobacteria, Planctomycetes, as well as Proteobacteria of the alpha and gamma classes, typical of soils, were detected; their relative abundancies decreased with depth. The phylum Verrucomicrobia was dominated by Candidatus Udaeobacter, aerobic heterotrophs capable of generating energy through the oxidation of hydrogen present in the atmosphere in trace amounts. Archaea made up a small part of the communities and were represented by thermophilic ammonium-oxidizers. Overall, the community was dominated by bacteria, whose cultivated relatives are able to obtain energy through the oxidation of the main components of coal gases, hydrogen and carbon monoxide, under aerobic conditions.