After a brief exposition to glucose, Thiobacillus acidophilus was isolated from a culture of iron-grown T. ferrooxidans. Physicochemical analysis of its DNA showed a G+C content of 62.9-63.2%. The new isolate grows best at 25-30 degrees C and at pH 3.0. Growth is possible between pH 1.5 and 6.0. Thiobacillus acidophilus is apparently strictly aerobic. Ammonium salts are the only suitable source of nitrogen. The bacterium is a facultative autotroph. In addition to elemental sulfur, it obtains energy from organic compounds such as D-glucose, D-galactose, D-fructose, D-mannitol, D-xylose, D-ribose, D-arabinose, L-arabinose, sucrose, sodium citrate, malic acid,dl-aspartic acid, and dl-glutamic acid. Thiobacillus acidophilus possesses the key enzymes of the tricarboxylic acid (TCA) cycle including NAD-and NADP-linked isocitric dehydrogenase and alpha-ketoglutarate dehydrogenase, and the key enzymes of the hexose monophosphate pathway (glucose-6-phosphate and 6-phosphogluconate dehydrogenase, and fructose 1,6-diphosphate aldolase). NADH oxidase has been found in particulate fraction of extracts. Rhodanese and thiosulfate oxidase have also been detected.

An acidophilic, disulfide-oxidizing, mesophilic, aerobic bacterium was isolated from wastewater sludge. The new organism is a gram-positive sporulated rod. It can use elemental sulfur and pyrite as sole energy sources and grows on organic substrates such as glutamate and glucose. It also grows on the following organic sulfur substrates: oxidized and reduced glutathione, cysteine, cystine, and dithio(bis) benzothiazole and clearly shows a preference for disulfide bond-containing substrates. The optimal pH of growth is between 1.5 and 2.5, depending on the substrate used, and the growth temperature range varies from 4 to 40°C, with an optimal value at 35°C. The G+C chromosomal DNA content was measured at 53 A 1 mol%. Phylogenetic analysis of 16s genes coding for rRNA sequences places the new isolate in the genus Sulfobacillus. In addition, unique phenotypic and physiologic characteristics and DNA homology values assign the isolate to a new species in the genus. Therefore, this new isolate has been named Sulfobacillus disulJidooxidans and has been assigned ATCC number 51911.Many facultatively heterotrophic bacteria are known for their ability to grow under highly acidic conditions. Some of these within the genera Sulfolobus (5) and Acidianus (31) are extremely thermophilic archaebacteria. They obtain their energy by the oxidation or reduction of elemental sulfur or from organic substrates. Others are mesophilic gram-negative bacteria belonging to the genus Acidiphilium (2, 18) and are able to use organic substrates at pH 3.0 or belong to the genus Thiobacillus, such as Thiobacillus acidophilus (17), which is also known for its ability to grow with elemental sulfur or glucose at pH 2.5.However, the only acidophilic, facultatively autotrophic, gram-positive, spore-forming bacillus so far characterized is Sulfobacillus thermosu&dooxidans (16), together with two subspecies ("themzotolerans" and "asporogenes") that do not produce spores (19). Golovacheva and Karavaiko (16) first described the genus Sulfobacillus in 1978 as gram-positive, sporeforming bacteria growing on elemental sulfur, ferrous iron, and other metal sulfides. The rod-shaped cells were described as fairly pleomorphic. The spores were spherical or slightly oval, terminal, subterminal, or paracentral. S. therrnosulfdooxidans is a typical acidophilic, thermotolerant, and facultatively autotrophic bacterium. Since then, four isolates which are gramvariable, thermotolerant acidophiles have been recovered from mines: ALV (27), BC (27), C-MT1(15), and TH3 (4), and have been described as belonging presumably to this genus. Some other gram-positive bacteria from the genus Alicyclobacillus (7-9) can also grow under acidic conditions, but they are heterotrophic bacteria.This work reports on the isolation and characterization of a new facultatively autotrophic, mesophilic, acidophilic, grampositive, spore-forming bacterium (SD-11) that could belong to the genus Sulfobacillus. MATERIALS AND METHODSBacterial strains and culture conditions. The acidophilic strain SD-1...

The microbiological oxidation of ferrous iron in batch and continuous systems has been investigated in relation to uranium extraction from a low-grade ore by Thiobacillus ferrooxidans. The influence of the parameters, agitation, and aeration on oxygen saturation concentration, rate of oxygen mass transfer, and rate of ferrous iron oxidation was demonstrated. The kinetic values, Vmax and K were determined using an adapted Monod equation for different dilution rates and initial concentrations of ferrous iron. The power requirements for initial leaching conditions were also calculated. Uranium extraction as high as 68% has been realized during nine days of treatment. Regrinding the leach residue and its subsequent leaching yielded 87% uranium solubilization.

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A /8-lactamase isolated from a strain of Bacteroides fragilis subsp. fragilis possessed hydrolytic activity toward cefotaxime. This antibiotic was degraded to a lower extent than was cephalothin, cephaloridine, and cefamandole, whereas cefoxitin remained unaffected by the enzyme. Kinetic parameters V. and Km for cefotaxime were calculated at 0.172 ,umol/min and 1.1 x 10-2 mM, respectively.Cefotaxime is a new semisynthetic cephalosporin, which has been introduced mainly because ofits potent activity against gram-negative bacilli (3,5,12,13,15 RESULTSThe ultraviolet absorption spectrum of cefotaxime before and after degradation by ,8-lactamase of B. fragilis is presented in Fig. 1