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Abstract
A new species of coccoid methanogen was isolated from the surface sediments of Tar Pit Lake at the LaBrea Tar Pits in Los Angeles, Calif. Surface colonies of strain ZT (= OGC 1T) (T = type strain) were tan, circular, clear, and convex with entire edges. The cells were irregular, nonmotile, and coccoid (diameter, 0.4 to 2.0 µm) and grew by producing methane from H2-CO2 or formate but not from methanol, methylamines, or acetate. They exhibited a negative Gram reaction, had protein cell walls, and were susceptible to lysis by sodium dodecyl sulfate. They grew over a narrow pH range (pH 6.5 to 7.5), with fastest growth near pH 7, and they were mesophilic (growth was most rapid at 37°C). Cells grew fastest with 15 g or less of NaCl per liter of medium. We propose that this isolate be named as a new species of methanogen, Methanocorpusculum labreanum, with strain Z (= Oregon Graduate Center Collection strain OGC 1 = DSM 4855) as the type strain.
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