An embedded-atom-method potential for tantalum ͑Ta͒ has been carefully constructed by fitting to a combination of experimental and density-functional theory ͑DFT͒ data. The fitted data include the elastic constants, lattice constant, cohesive energy, unrelaxed vacancy formation energy, and hundreds of force data calculated by DFT for a variety of structures such as liquids, surfaces, clusters, interstitials, vacancies, and stacking faults. We also fit to the cohesive energy vs volume data from the equation of state for the body-centered-cubic ͑bcc͒ Ta and to the calculated cohesive energy using DFT for the face-centered-cubic ͑fcc͒ Ta structure. We assess the accuracy of the new potential by comparing several calculated Ta properties with those obtained from other potentials previously reported in the literature. In many cases, the new potential yields superior accuracy at a comparable or lower computational cost.

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Nine moderately alkalitolerant thermophilic bacteria with similar properties were isolated from water and soil samples obtained from Yellowstone National Park. These Gram-type-positive, rod-shaped bacteria produce cells with primary branches. The cells are peritrichous and exhibit only slight tumbling motility. At 60°C the pH range for growth is 6.9 to 10.3, and the optimum pH is 8.5. At pH 8.5 the temperature range for growth is 34 to 66OC, with an optimum temperature of 57OC. The strains are mainly proteolytic. The fermentation products from yeast extract are acetate, C02, and H,. Fumarate added to minimal medium containing yeast extract is stoichiometrically converted to succinate, indicating that it is used as an alternative electron acceptor. The DNA G+C content is 33 to 34 mol%. On the basis of its unique properties, such as branch formation, growth at alkaline pH values at elevated temperatures, and the relative distance of its 16s rRNA sequence from those of other known bacteria, we propose that strain JWIYL-l3ST (T = type strain) and eight similar strains represent a new genus and species, Anaerobrancu horikoshii. Strain JWW-138 is designated the type strain of the type species, A. horikoshii, which was named in honor of Koki Horikoshi, a pioneer in the field of alkaliphilic bacteria.There has been increasing interest in alkaliphilic bacteria in recent years. The reasons for this include potential industrial applications that require enzymes that are stable at a high pH values (pH 9.5 and above) and at temperatures above 50°C (10, 11,20,30). These applications include the use of proteases and xylanases for a nonchlorine bleaching process in the pulp and paper industry. Alkaliphilic bacteria have been isolated from a variety of environments. Most of these isolates, including Bacillus alcalophilus (39, belong to the genus Bacillus, and the optimum pH values of these organisms are between 10 and 11.5. Thus, most of the current information concerning alkaliphiles and pH-stable industrial enzymes has been obtained through studies of these aerobic organisms (11,14, 15). Among the anaerobes, many of the alkalitolerant organisms that have been isolated are Archaea (20). These include methanogens such as Methanobacterium alcaliphilum (42), Methanobacterium arbophilicum (43), and Methanococcus vannielii (33), which have optimum pH values ranging from 7.0 to 9.0, and halophilic methanogens such as Methanohalophilus zhilinae, which has the highest optimum pH reported for a member of the Archaea (pH 9.2) (23). Very little is known about the anaerobic alkalitolerant (eu)bacteria, which include one unnamed anaerobe (31) and four unnamed halophilic mesophiles that grow at pH values between 6.5 and 10.0 (20). One facultative anaerobe, Amphibacilhs xylanus, which grows at pH values between 8.0 and 10.0 (25), has also been described.Only a few of the known alkaliphiles are also (moderate) thermophiles. The highest recorded growth temperature for an aerobic alkaliphilic Bacillus strain is 57°C (11). Among the Archaea, Meth...

More than 40 isolates of a novel, ubiquitous, proteolytic, moderately alkaliphilic, thermophilic obligate anaerobe were obtained from geothermally and anthropogenically heated environments and mesobiotic environments located on three continents. Whole-cell protein sodium dodecyl sulfate gel electrophoresis revealed that most of these organisms are very similar. Eight of the isolates were characterized in detail; this analysis included 16s ribosomal DNA sequence analysis. The cells of those organisms are (depending on the isolate) 0.5 to 0.8 pm in diameter and 1.5 to 13 pm long, exhibit tumbling motility, and have a positive Gram stain reaction. The temperature range for growth is 43" to 75°C (optimum temperature, 66"C), and the pH range for growth is 5.4 to 9.5 (optimum pH, 8.2); the shortest doubling time is around 10 min. Yeast extract is required for growth, and (depending on the strain) glucose, sucrose, fructose, galactose, and ribose are utilized. The fermentation products from glucose in the presence of yeast extract are CO,, H2, acetate, formate, and ethanol. The G+C content is 30 to 31 mol%. On the basis of these properties, which differentiate these strains from all alkalitolerant thermophiles described previously, and the results of a comparison of the 16s ribosomal DNA sequences of these organisms with previously described sequences, we propose that our isolates be placed in a single species of the new genus Therrnobrachiurn; strain JWm-NZ35 is the type strain of the the type species, Them0 brachiurn celere.There are relatively few alkaliphilic environments that occur naturally (13, 34). The most common and best-studied alkaliphilic environments are the soda lakes and deserts that have pH values of 10 to 11.5 (10). These environments usually result from the presence of large amounts of sodium carbonate and other salts (17). However, alkaline conditions can also be found in niches of other environments in which the pH of a microenvironment can be different from the pH of the environment as a whole (17).Only a few thermophiles are able to grow at pH values of more than 9.0 (31). Aside from characterizations of recently described anaerobic alkalithermophiles (5,14, 15,34), our knowledge of alkaliphilic bacteria is based mainly on the characteristics of Bacillus species (13, 20, 21). In this paper, we describe a novel, ubiquitous, moderately alkaliphilic, anaerobic thermophile, Thermobrachium celere, which was isolated from samples obtained from various mesobiotic and thermobiotic environments on three continents; the pH values of these samples ranged from 4.8 to 9.0. MATERIALS AND METHODSSample collection. Separated and mixed sediment and water samples were obtained from various locations by completely filling 100-to 500-ml sterile glass jars which had been flushed with nitrogen and were sealed with butyl rubber stoppers. Although the samples were kept at temperatures below 10°C as much as possible during transport to the laboratory in Athens, Ga., they were temporarily exposed to ambient temperatures f...

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