Extracellular proteases from 8 Antarctic psychrotolerant Pseudomonas sp. strains were purified and characterised. All of them are neutral metalloproteases, have an apparent molecular mass of 45kDa, optimal activity at 40 degrees C and pH 7-9, retaining significant activity at pH 5-11. With the exception of P96-18, which is less stable, all retain more than 50% activity after 3 h of incubation at pH 5-9 and show low thermal stability (their half-life times range from 20 to 60 min at 40 degrees C and less than 5 min at 50 degrees C). These proteases can be used in commercial processes carried out at neutral pH and moderate temperatures, and are of special interest for their application in mixtures of enzymes where final thermal selective inactivation is needed. Results also highlight the relevance of Antarctic biotopes for the isolation of protease-producing enzymes active at low temperatures.

Affiliations of the dominant culturable bacteria isolated from Potter Cove, South Shetland Islands, Antarctica, were investigated together with their production of cold-active hydrolytic enzymes. A total of 189 aerobic heterotrophic bacterial isolates were obtained at 4°C and sorted into 63 phylotypes based on their amplified ribosomal DNA restriction analysis profiles. The sequencing of the 16S rRNA genes of representatives from each phylotype showed that the isolates belong to the phyla Proteobacteria (classes Alpha- and Gamma-proteobacteria), Bacteroidetes (class Flavobacteria), Actinobacteria (class Actinobacteria) and Firmicutes (class Bacilli). The predominant culturable group in the site studied belongs to the class Gammaproteobacteria, with 65 isolates affiliated to the genus Pseudoalteromonas and 58 to Psychrobacter. Among the 189 isolates screened, producers of amylases (9.5%), pectinases (22.8%), cellulases (14.8%), CM-cellulases (25.4%), xylanases (20.1%) and proteases (44.4%) were detected. More than 25% of the isolates produced at least one extracellular enzyme, with some of them producing up to six of the tested extracellular enzymatic activities. These results suggest that a high culturable bacterial diversity is present in Potter Cove and that this place represents a promising source of biomolecules

We have studied laminated sediments from Lake Esmeralda, Vega Island, in order to reconstruct its history. We describe both inorganic and organic components of the sediment using a combination of the following analytical methods: x-ray fluorescence (XRF), x-ray diffraction (XRD), magnetic susceptibility measurement, chemical analysis for determination of cation exchange capacity, grain size determination, geochemical analyses (total inorganic carbon (TIC), total organic carbon (TOC), total sulphur (TS)), spectrophotometry, high-pressure liquid chromatography, and diatom assemblage and faunal remains characterization. The geochronology of the core was based on modelling optically stimulated luminescence ages and supported by laminae counting. The dating results imply a maximum age of ~400 years for the 177-cm long core and a period covered of ~200 years, suggesting (quasi-)annual laminae formation. Such a young age contradicts previous findings based on radiocarbon dating. Geomorphological evidence indicates that river capture isolated the lake catchment from upslope sediment delivery, effectively terminating accumulation ~230 years ago. Conversely, our short-term palaeoenvironmental record yields a subdecadal temporal resolution, which is unparalleled in comparison with other Antarctic palaeolimnological studies. Our interpretations of the geochemical and mineralogical proxy data give us insight into the past lake catchment and waterbody evolution, and lead us to recognize periods of enhanced weathering, bottom anoxia and to distinguish major lake level changes.

A marine bacterial strain, designated strain JUB59 T , was isolated from surface seawater in Antarctica and subsequently characterized. Cells were found to be Gram-negative, non-motile rods forming butyrous, shiny, yellowish orange colonies on marine agar. Growth occurred at 2-28 6C (optimally at 22-25 6C) but not at 30 6C; Na + ions were required, but 9 % NaCl (w/v) was not tolerated. Phylogenetic analysis, based on comparisons of the complete 16S rRNA gene sequence of the novel isolate with the sequences of closely related strains, showed that strain JUB59 T belonged to the family Flavobacteriaceae, representing a novel species of the genus Bizionia. The highest levels of sequence similarity were found with respect to Bizionia myxarmorum ADA-4 T (97.4 %) and Bizionia algoritergicola APA-1 T (97.1 %). However, the DNA-DNA relatedness of strain JUB59 T with respect to these two strains was low (15.9-17.3 and 19.3-22.1 %, respectively). The predominant fatty acids of strain JUB59 T were iso-15 : 1v10c (18.1 %), iso-15 : 0 (17.3 %), anteiso-15 : 0 (13.9 %), iso-17 : 0 3-OH (9.2 %), 15 : 0 (6.0 %) and iso-16 : 0 3-OH (5.3 %). The main polar lipids were phosphatidylethanolamine, an aminolipid, an amino-positive phospholipid and two unidentified lipids. MK-6 was the major respiratory quinone (.90 %) and the DNA G+C content was 34 mol%. On the basis of the data obtained, strain JUB59 T represents a novel species of the genus Bizionia, for which the name Bizionia argentinensis sp. nov. is proposed. The type strain is JUB59 T (5DSM 19628 T 5CCM-A-29 1259 T ).The family Flavobacteriaceae (Bernardet et al., 1996(Bernardet et al., , 2002 currently comprises more than 40 genera. Many of these genera group strains that have been recovered from a variety of marine habitats (Bernardet & Nakagawa, 2006). These genera form a distinct 'marine clade' in phylogenetic trees based on 16S rRNA gene sequences (Bowman, 2004;Bowman & Nichols, 2005;Bowman, 2006). Marine members of the family occur in tropical, temperate (Nedashkovskaya et al., 2004;Jung et al., 2005;Kwon et al., 2006) and polar (Bowman, 2000;Bowman & Nichols, 2002;Yi et al., 2005) marine environments, where they play an important role in the mineralization of organic matter, especially following algal blooms (Bowman et al., 1997;Pinhassi et al., 2004). The genus Bizionia belongs to the marine clade of the family Flavobacteriaceae. First described by Nedashkovskaya et al. (2005), the genus currently comprises five species, isolated from sea-ice brine and various marine invertebrates: Bizionia paragorgiae (Nedashkovskaya et al., 2005), B. saleffrena, B. gelidisalsuginis, B. algoritergicola and B. myxarmorum (Bowman & Nichols, 2005). In this study, a bacterial strain isolated from seawater in Antarctica was analysed by a polyphasic taxonomic approach and was found to represent a novel member of the genus Bizionia. B. saleffrena HFD T , B. gelidisalsuginis IC164 T , B. algoritergicola APA-1 T and B. myxarmorum ADA-4 T were used as reference strains for all of the physiolog...

No abstract