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Mutations causing requirements for histidine, purine, and vitamin B12 were obtained in strain PS of Methanococcus voltae (archaebacteria) upon irradiation with UV or gamma rays. The first two miutations were shown to revert at low frequencies and were used to demonstrate the occurrence of transformation with homologous, wild-type DNA. The transformation rates obtained for these presumably chromosomal markers were in the range of 2 to 10O transformants per ,ug of DNA. Mutants resistant to 2-bromoethanesulfonate and to 5-methyl-DL-tryptophan were also isolated.

An acetate-fermenting strain of Methanosarcina was isolated from an acetate enrichment culture inoculated with anaerobic sludge from a waste treatment digestor. In pure culture, this organism fermented acetate in the absence of added hydrogen at rates comparable in magnitude to those found in digestor systems. This rate was significantly higher than previously obtained for pure cultures of this genus. Mineral components of yeast extract were highly stimulatory for cultures growing on methanol. Comparable stimulation was not observed for cultures growing on acetate. Labeling studies indicated that acetate was converted to methane and CO2 as predicted by previous studies on mixed cultures. Total oxidation or reduction of acetate was not the mechanism of conversion of acetate to methane by the pure culture. The ability of this strain to form colonies or to produce methane from acetate was apparently influenced by the choice of substrate and conditions used for growing the inoculum.

An anaerobic, extremely thermophilic, xylanolytic, non-spore-forming bacterium was isolated from a sediment sample taken from Owens Lake, California, and designated strain OLT (T = type strain). Strain OLT had a Gramnegative reaction and occurred as short rods which sometimes formed long chains containing a f e w coccoid cells. It grew a t 50-80 "C, with an optimum a t 75 "C. The pH range for growth was 55-900 with an optimum a t about pH 7.5. When grown on glucose a t optimal conditions, its doubling time was 7-3 h. In addition to glucose, the isolate utilized sucrose, xylose, fructose, ribose, xylan, starch, pectin and cellulose. Yeast extract stimulated growth on carbohydrates but was not obligately required. The end products from glucose fermentation were lactate, acetate, ethanol, H, and CO, . The G+C content of strain OLT was 36.6 mol%. The 165 rDNA sequence analysis indicated that strain OLT was a member of the subdivision containing Gram-positive bacteria with DNA G+C content of less than 55 mol% and clustered with members of the genus Caldicellulosiru~ tor. Because s tra i n OLT is p h y log ene t ica I I y and p he no typ ica I I y different from other members of this genus, it is proposed to designate this isolate Caldicellulosiruptor owensensis sp. nov. Strain OLT is the type strain (= ATCC 7001673.

An acetate enrichment culture was initiated by inoculating anaerobic sludge Viologen dye inhibition of methane formation by Methanobacillus omelianskii. J. Bacteriol. 87:993-998. on July 31, 2020 by guest http://aem.asm.org/ Downloaded from

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A strictly anaerobic, moderately halophilic, gram-negative, rod-shaped bacterium was isolated from Great Salt Lake, Utah, sediments and designated GSLST (T = type strain). Strain GSLST grew optimally at pH 6.7 to 7.0 but had a very broad pH range for growth (pH 5.8 to 10.0). The optimum temperature for growth was 37"C, and no growth occurred at 15 or 55°C. The optimum salt concentration for growth was 10%. Strain GSLST required yeast extract and Trypticase peptone to ferment carbohydrates, pyruvate, and glycine betaine. Strain GSLST was resistant to penicillin, D-cycloserine, tetracycline, and streptomycin. The G+C content of this isolate was 31 mol%. The fermentation products from glucose utilization were acetate, butyrate, lactate, CO,, and H,, and in addition strain GSLST fermented glycine betaine to acetate and trimethylamine. All of these traits distinguish this organism from all previously described halophilic anaerobes. The 16s rRNA gene sequence of strain GSLST was found to be similar to, but also significantly different from, the 16s rRNA sequences of Haloanuerobium sahugo and Haloanaerobium praevalens. Therefore, strain GSLST ( = DSM 827ST) is described as a new species, Haloanaerobium alcaliphilum.

Methanosarcina barkeri strain 227 maintained on an acetate medium for 2 years was found to possess hydrogenase, methylcoenzyme M methylreductase, coenzyme F420, and coenzyme M. The levels of these constituents in acetate-grown cells were similar to those found in cells of the same strain grown on methanol or hydogen and carbon dioxide.