Moorella stamsii sp nov., a new anaerobic thermophilic hydrogenogenic carboxydotroph isolated from digester sludge

A novel anaerobic, thermophilic, carbon monoxide-utilizing bacterium, strain E3-O-T, was isolated from anaerobic sludge from a municipal solid waste digester. Cells were straight rods, 0.6-1 mu m in diameter and 2-3 mu m in length and grew as single cells or in pairs. Cells formed round terminal endospores. The temperature range for growth was 50-70 degrees C, with an optimum at 65 degrees C. The pH range for growth was 5.7-8.0, with an optimum at 7.5. Strain E3-O-T had the ability to ferment various sugars, such as fructose, galactose, glucose, mannose, raffinose, ribose, sucrose and xylose, producing mainly H-2 and acetate. In addition, the isolate was able to grow with CO as the sole carbon and energy source. CO oxidation was coupled to H-2 and CO2 formation. The G +C content of the genomic DNA was 54.6 mol%. Based on 16S rRNA gene sequence analysis, this bacterium is most closely related to Moorella glycerini (97% sequence identity). Based on the physiological features and phylogenetic analysis, it is proposed that strain E3-O-T should be classified in the genus Moorella as a representative of a novel species, Moorella stamsii. The type strain of Moorella stamsii is E3-O-T (=DSM 26271(T)=CGMCC 1.5181(T)).