Emendation of the Genus Thermobacteroides: Thermobacteroides proteolyticus sp. nov., a Proteolytic Acetogen from a Methanogenic Enrichment

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Abstract
Thermobacteroides proteolyticus sp. nov. was isolated from a methanogenic enrichment culture inoculated from a thermophilic digestor (55°C) that was fermenting tannery wastes and cattle manure. The cells were anaerobic, gram-negative, nonsporeforming, nonmotile rods that were 0.5 μm wide and 1 to 6 μm long. At the end of logarithmic growth, they were pleomorphic, with some filamentous cells. The deoxyribonucleic acid base composition was 45 mol% guanine plus cytosine. The temperature optimum was 63°C (growth range 35, to 75°C); the pH optimum was 7.5 (growth range, pH 5.0 to 8.5). The growth substrates used included yeast extract, peptone, casein, gelatin, and Trypticase peptone. Fructose, glucose, maltose, sucrose, and mannose were weakly used as growth substrates; however, addition of yeast extract and either rumen fluid or Trypticase peptone stimulated utilization of these carbohydrates. Acetate, H2, and CO2 were the major products of growth in medium containing gelatin or glucose. The cells were resistant to kanamycin. The type strain is strain BT (= ATCC 35242).