Characterization of a novel bacteriumoriginating from a biogas process

Abstract: An anaerobic bacterium, isolated from an enrichment culture originating from a biogas reactor operating at high ammonia conditions, was characterised via various tests. An analysis of the 16S rRNA gene confirmed that the closest relative was Desulfotomaculum halophilum with 92,5 % similarity. The isolated bacterium had a narrow substrate range and only used three compounds for growth, which of pyruvate was the optimal, used as a substrate for most inoculations in this study. Lactate was also tested as substrate, together with sulphate to evaluate if the isolate could use it as an electron acceptor. Neither of those inoculations formed growth. The bacterium ferments pyruvate and acetate are formed. It is a gram positive mesophilic bacterium and growth was measured between 25 °C and 38.5 °C. It grows well in high concentrations of ammonia, tested up to 0.24 M, and can also grow in high sodium salinity, here tested until 0.18 M. Microscopic analyses showed that the cells are rod shaped and they move by twisting around. The described bacterium is most likely a new species.