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Abstract
Most probable numbers for Syntrophomonas-like bacteria degrading stearate were 1.5 x 106 to 4.6 x 106, 2.4 × 105, and 4.6 × 102 cells per ml of municipal anaerobic digester sludge, swine waste lagoon sediment, and cow ruminai fluid, respectively. Strain SD2, which was isolated from digestor sludge in coculture with the H2-utilizing bacterium Desulfovibrio sp. strain G-11, plus sulfate, was a long-chain saturated fatty-acid-using bacterium identified as a strain of the genus Syntrophomonas. Strain SD2 differed from Syntrophomonas wolfei subsp. wolfei subsp. nov. in its usually smaller size and in its ability to catabolize C9 to C18 saturated fatty acids. It differed from Syntrophomonas sapovorans in not needing relatively high concentrations of Ca2+ and in its inability to catabolize unsaturated fatty acids, such as oleic or linoleic acid. A strain SD2 coculture was further adapted to grow on crotonate and was subsequently purified without sulfate, with cells of strain G-11 only rarely seen. A 16S ribosomal ribonucleic acid sequence analysis (H. Zhao, D. Yang, C. Woese, and M. P. Bryant, manuscript in preparation) indicated that strain SD2 is phylogenetically very closely related to S. wolfei. Thus, we propose the name Syntrophomonas wolfei subsp. saponavida for this organism (strain DSM 4212T) (T = type strain) because of its ecologically important ability to use stearate and other long-chain saturated fatty acids. Emended descriptions of the genus and species are given.
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