Catalase from the facultatively psychrophilic bacterium Vibrio rumoiensis S-1 T , which was isolated from an environment exposed to H 2 O 2 and exhibited high catalase activity, was purified and characterized, and its localization in the cell was determined. Its molecular mass was 230 kDa, and the molecule consisted of four identical subunits. The enzyme, which was not apparently reduced by dithionite, showed a Soret peak at 406 nm in a resting state. The catalytic activity was 527,500 U ⅐ mg of protein ؊1 under standard reaction conditions at 40°C, 1.5 and 4.3 times faster, respectively, than those of the Micrococcus luteus and bovine catalases examined under the same reaction conditions, and showed a broad optimum pH range (pH 6 to 10). The catalase from strain S-1 T is located not only in the cytoplasmic space but also in the periplasmic space. There is little difference in the activation energy for the activity between strain S-1 T catalase and M. luteus and bovine liver catalases. The thermoinstability of the activity of the former catalase were significantly higher than those of the latter catalases. The thermoinstability suggests that the catalase from strain S-1 T should be categorized as a psychrophilic enzyme. Although the catalase from strain S-1 T is classified as a mammal type catalase, it exhibits the unique enzymatic properties of high intensity of enzymatic activity and thermoinstability. The results obtained suggest that these unique properties of the enzyme are in accordance with the environmental conditions under which the microorganism lives.

A novel, facultatively psychrophilic alkaliphile that grows on a chemically defined medium containing n-alkanes as the sole carbon source was isolated from a drain of a fish product-processing plant. The isolate was an aerobic, non-motile, Gram-positive bacterium. The bacterium was catalase-positive and oxidase-negative. The cell wall contained meso-diaminopimelic acid, arabinose and galactose ; the glycan moiety of the cell wall contained acetyl residues. The GMC content of the DNA was 69 6 mol %. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate was closely related to members of the genus Dietzia (96 1-96 8 % similarity). Comparisons of phenotypic and chemotaxonomic characteristics between the isolate and the two known Dietzia species showed that they were very similar. However, the isolate differed from the two known Dietzia species in growth temperature range and certain physiological characteristics. DNA-DNA hybridization revealed that the isolate had 38 4 and 49 7 % relatedness, respectively, to Dietzia maris and Dietzia natronolimnaea. On the basis of the physiological and biochemical characteristics, the phylogenetic position as determined by 16S rRNA gene analysis and DNA-DNA relatedness, it is concluded that the isolate should be designated as a novel species, for which the name Dietzia psychralcaliphila sp. nov. is proposed. The type strain is ILA-1 T (l JCM

The sporicidal activity of ozone in the gas phase was investigated. Spores of six strains of Bacillus species deposited on filter paper or glass fibre filter were conditioned at different relative humidities (r.h.), and then exposed to ozone ranging in concentration from 0.5 to 3.0 mg/l at different r.h. There was a lag phase in the initial stage of exposure followed by an exponential decrease in the number of survivors with time, although no lag phase was observed with one strain. Inactivation rates increased with increasing exposure r.h. while no significant inactivation was attained at a r.h. of 50% or below. The conditioning r.h. influenced the duration of the lag phase. The D-values (decimal reduction time) in the logarithmic phase varied roughly in inverse proportion to the ozone concentration.

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...

We revealed the micromagnetic structure of an Fe thin film exchange interacting with the spins of a fully compensated (001) surface of antiferromagnetic NiO. The interface exchange interaction causes the Fe domains to follow the NiO domains. The Fe spin polarization is in plane and the spin polarization in each domain is roughly perpendicular to an easy-spin axis of the NiO. These results agree with numerically calculated spin directions. Our numerical results also show that the NiO spins at the interface cant from the easy-spin axis towards the Fe spin because of exchange coupling.