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...

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