A novel alkaliphile was isolated from a drain of a fish processing plant. The isolate grew at a pH range of 7-10. Cells were Gram-positive, facultatively aerobic, motile rods with peritrichous flagella. Colonies were orange or yellow in colour. Catalase and oxidase reactions were positive. The isolate grew in 0-12 % NaCl but not above 15 % NaCl. Its cell extract exhibited 567 times higher catalase activity than an Escherichia coli cell extract. The major cellular fatty acids were iso-C 13 : 0 , anteiso-C 13 : 0 , iso-C 15 : 0 , iso-C 16 : 0 , iso-C 17 : 0 , anteiso-C 17 : 0 and iso-C 17 : 1 . Its DNA G+C content was 46?7 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing and chemotaxonomic data indicated that strain T-2-2 T is a member of the genus Exiguobacterium. DNA-DNA hybridization revealed a low relatedness of the isolate to several phylogenetic neighbours (less than 25 %). On the basis of phenotypic characteristics, phylogenetic data and DNA-DNA relatedness data, the isolate merits classification as a novel species, for which the name Exiguobacterium oxidotolerans sp. nov. is proposed. The type strain is T-2-2 T (=JCM 12280 T =NCIMB 13980 T ).There are micro-organisms living in environments of extreme temperature, pH, salinity and hydropressure (Horikoshi & Grant, 1991). These micro-organisms have apparently acquired the ability to survive under such environmental conditions through long-term evolutionary processes, and they possess specific mechanisms for survival in such extreme environments. Among such adaptational processes, not only the micro-organisms themselves might be affected by environmental conditions and induced to acquire adaptation-suitable features, but so too might production of organic molecules within the micro-organisms, such as enzymes and proteins that sustain their metabolism. Although H 2 O 2 production and interaction with micro-organisms often occur in nature (Haas & Goebel, 1992), there have been only a few reports of specific micro-organisms that inhabit environments with hyperoxidative stress caused by factors such as high H 2 O 2 concentrations (Yumoto et al., 1999).Aerobic organisms normally possess specific enzymes to eliminate H 2 O 2 , which are produced extracellularly as well as intracellularly. Catalase is one such well-known enzyme. It has been reported that catalase plays an important role in certain micro-organisms in obtaining niches in host cells. For example, in Vibrio fischeri, catalase KatA is required for its colonization of the light organ of squid (Visick & Ruby, 1998). The production of catalase and H 2 O 2 has been reported in several other cases of either parasitic or symbiotic relationships between microorganisms and their host (Katsuwon & Anderson, 1992;Rocha et al., 1996). If there is a micro-organism that is able to survive in an environment with high H 2 O 2 concentrations, it can be expected that this micro-organism will possess an enzyme (e.g. catalase) exhibiting a high H 2 O 2 -degrading ability. In the present study, we isolated a mic...

A heterotrophic nitrifying bacterium, designated strain DA2 T , was isolated from a microbiological agent for enhancing microbial digestion in sewage treatment tanks. Cells of strain DA2 T were Gram-positive, facultatively anaerobic, sporulating rods that were motile by means of peritrichous flagella; they were able to grow at pH 5-8. The major isoprenoid quinone of strain DA2 T was menaquinone-7 (MK-7) and its cellular fatty acid profile consisted mainly of iso-C 15 : 0 (18.6 %) and anteiso-C 15 : 0 (69.1 %). The DNA G+C content was 54.1 mol%. 16S rRNA gene sequence phylogeny suggested that strain DA2 T is a member of the genus Brevibacillus, with highest sequence similarities (in parentheses) to the type strains of Brevibacillus choshinensis (99.7 %), B. formosus (99.4 %), B. brevis (99.4 %), B. agri (99.0 %), B. reuszeri (98.8 %), B. parabrevis (98.7 %), B. centrosporus (98.6 %), B. limnophilus (97.4 %), B. panacihumi (97.3 %) and B. invocatus (97.3 %). DNA-DNA hybridization showed less than 60 % relatedness between strain DA2 T and type strains of the most closely related species given above. Given the significant differences in phenotypic and chemotaxonomic characteristics, and phylogenetic analysis based on the 16S rRNA sequence and DNA-DNA relatedness data, the isolate merits classification as a novel species, for which the name Brevibacillus nitrificans is proposed; the type strain of this species is DA2 T (5JCM 15774 T 5NCIMB 14531 T ).

A psychrotolerant and H2O2-resistant bacterium, Exiguobacterium oxidotolerans T-2-2T, exhibits extraordinary H2O2 resistance and produces catalase not only intracellularly but also extracellularly. The intracellular and extracellular catalases exhibited the same enzymatic characteristics, that is, they exhibited the temperature-dependent activity characteristic of a cold-adapted enzyme, their heat stabilities were similar to those of mesophilic enzymes and very high catalytic intensity. In addition, catalase gene analysis indicated that the bacterium possessed the sole clade 1 catalase gene corresponding to intracellular catalase. Hence, intracellular catalase is secreted into the extracellular space. In addition to intracellular and extracellular catalases, the inner circumference of the cells showed the localization of catalase in the mid-stationary growth phase, which was observed by immunoelectron microscopy using an antibody against the intracellular catalase of the strain. The cells demonstrated higher catalase activity in the mid-stationary growth phase than in the exponential growth phase. The catalase localized in the inner circumference can be dissociated by treatment with Tween 60. Thus, the localized catalase is not tightly bound to the inner circumference of the cells and may play a role in the oxidative defense of the cells under low metabolic state.

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