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Molecular Analysis of Geographic Patterns of Eukaryotic Diversity in Antarctic Soils. Blair Lawley, 2004.We describe the application of molecular biological techniques to estimate eukaryotic diversity (primarily fungi, algae, and protists) in Antarctic soils across a latitudinal and environmental gradient between approximately 60 and 87°S . The data were used to (i) test the hypothesis that diversity would decrease with increasing southerly latitude and environmental severity, as is generally claimed for "higher" faunal and plant groups, and (ii) investigate the level of endemicity displayed in different taxonomic groups . Only limited support was obtained for a systematic decrease in diversity with latitude, and then only at the level of a gross comparison between maritime (Antarctic Peninsula/Scotia Arc) and continental Antarctic sites . While the most southerly continental Antarctic site was three to four times less diverse than all maritime sites, there was no evidence for a trend of decreasing diversity across the entire range of the maritime Antarctic (60 to 72°S) . Rather, we found the reverse pattern, with highest diversity at sites on Alexander Island (ca . 72°S), at the southern limit of the maritime Antarctic . The very limited overlap found between the eukaryotic biota of the different study sites, combined with their generally low relatedness to existing sequence databases, indicates a high level of Antarctic site isolation and possibly endemicity, a pattern not consistent with similar studies on other continents . Molecular Analysis of the Gene Encoding a Novel Cold-Adapted Chitinase (ChiB) from a Marine Bacterium, Alteromonas sp . Strain O-7. Hideyuki Orikoshi, 2003.The chitinase B (ChiB) secreted by Alteromonas sp . strain O-7 was purified, and the corresponding gene (chiB) was cloned and sequenced . The open reading frame of the chiB gene encodes a protein of 850 amino acids with a calculated molecular mass of 90,223 Da . ChiB is a modular enzyme consisting of two reiterated domains and a catalytic domain belonging to chitinase family 18 . The reiterated domains are composed of chitin-binding domain (ChtBD) type 3 and two fibronectin type III (Fn3)-like domains . Expression plasmids coding for ChiB or deletion derivatives thereof were constructed in Escherichia coli . Deletion analysis showed that the ChtBD of ChiB plays an important role in efficient hydrolysis of insoluble chitin . The optimum pH and temperature of ChiB were 6.0 and 30°C, respectively . The enzyme showed relatively high catalysis, even at low temperatures close to 0°C, and remarkable thermal lability compared to ChiA and ChiC, which are the mesophilic chitinases of the same strain . The kcat/Km value for the ChiB reaction at 10°C was about 4.7 times higher than that of ChiC . These results suggest that ChiB is a cold-adapted enzyme . The RNA transcript of chiB was induced by 1% GlcNAc, and along with a rise in temperature, the RNA transcript showed a tendency to decrease . Thus, among the ChiA, ChiB, and ChiC chitinases, production of ChiB may be advantageous for the strain, allowing it to easily acquire nutrients from chitin and to survive in cold environments . Behavior of Psychrotrophic Lactic Acid Bacteria Isolated from Spoiling Cooked Meat Products. Yoshikatsu Hamasaki, 2003.Three kinds of lactic acid bacteria were isolated from spoiling cooked meat products stored below 10°C . They were identified as Leuconostoc mesenteroides subsp . mesenteroides, Lactococcus lactis subsp . lactis, and Leuconostoc citreum . All three strains grew well in MRS broth at 10°C . In particular, L . mesenteroides subsp . mesenteroides and L . citreum grew even at 4°C, and their doubling times were 23.6 and 51.5 h, respectively . On the other hand, although the bacteria were initially below the detection limit (<10 CFU/g) in model cooked meat products, the bacterial counts increased to 108 CFU/g at 10°C after 7 to 12 days .
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