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Regions with extreme environmental conditions can be considered as a system with unique biodiversity and potential. The aim was to determine resistance range to UVirradiation, temperature and concentration of NaCl, the glycosidase and proteolytic activity of bacteria isolated from terrestrial ecosystems of Antarctica, Ecuador and Israel. Methods. The objects of study were 19 extremе-tolerant bacteria. UV-irradiation of bacteria was performed with a BUF-15 lamp (λ = 254 nm) in the range of 37-1440 J/m². The temperature range of growth was determined at a temperature of 1-42 ºC, halotolerance -- at NaCl concentration of 1-100 g/l. Enzymes activities were studied in the culture supernatant. To determine glycosidase activities, p-nitrophenyl substrates, galactomannan guar and soluble starch were used. Casein and elastin were used as substrates for the determination of proteolytic activity. Results. Antarctic pigmented microorganisms showed a higher resistance to UV than non-pigmented. Cultures from highland biotopes and saline soils were resistant to UV-doses of 400-1440 J/m². Investigated strains mainly belonged to psychotolerant and moderately halophilic bacteria. Most of the strains showed α-amylase and/or β-mannanase activity. Two strains, 3271 and 3456, exhibited simultaneously four and five glycosidase activities respectively. Caseinolytic activity was observed in 17 cultures, elastase -- in one. Conclusions. Ecophysiological characteristics of the studied cultures reflect their adaptation to extreme environmental conditions. Both pigmented and non-pigmented microorganisms were resistant to UV-radiation, most of them are psychrotolerant moderate halophiles with α-amylase, β-mannanase, caseinolytic and elastase activity. [ABSTRACT FROM AUTHOR]

Background: Halorubrum lacusprofundi is a cold-adapted halophilic archaeon isolated from Deep Lake, a perennially cold and hypersaline lake in Antarctica. Its genome sequencing project was recently completed, providing access to many genes predicted to encode polyextremophilic enzymes active in both extremely high salinity and cold temperatures. Results: Analysis of the genome sequence of H. lacusprofundi showed a gene cluster for carbohydrate utilization containing a glycoside hydrolase family 42 β-galactosidase gene, named bga. In order to study the biochemical properties of the β-galactosidase enzyme, the bga gene was PCR amplified, cloned, and expressed in the genetically tractable haloarchaeon Halobacterium sp. NRC-1 under the control of a cold shock protein (cspD2) gene promoter. The recombinant β-galactosidase protein was produced at 20-fold higher levels compared to H. lacusprofundi, purified using gel filtration and hydrophobic interaction chromatography, and identified by SDSPAGE, LC-MS/MS, and ONPG hydrolysis activity. The purified enzyme was found to be active over a wide temperature range (--5 to 60°C) with an optimum of 50°C, and 10% of its maximum activity at 4°C. The enzyme also exhibited extremely halophilic character, with maximal activity in either 4 M NaCl or KCl. The polyextremophilic β-galactosidase was also stable and active in 10-20% alcohol-aqueous solutions, containing methanol, ethanol, nbutanol, or isoamyl alcohol. Conclusion: The H. lacusprofundi β-galactosidase is a polyextremophilic enzyme active in high salt concentrations and low and high temperature. The enzyme is also active in aqueous-organic mixed solvents, with potential applications in synthetic chemistry. H. lacuprofundi proteins represent a significant biotechnology resource and for developing insights into enzyme catalysis under water limiting conditions. This study provides a system for better understanding how H. lacusprofundi is successful in a perennially cold, hypersaline environment, with relevance to astrobiology. [ABSTRACT FROM AUTHOR]

Abstract: The taxomony of strain CRSS (DSM 15686T=ATCC BAA-848T) isolated from Cape Russell in Antarctica (Ross Sea, 74 52.35 S 163 53.03 E) was investigated in a polyphasic approach. The morphological, physiological and genetic characteristics were compared with that of related species of the genus Halomonas. The isolate grew optimally at pH 9.0, 10% NaCl at 30°C. The cells were Gram-negative aerobic rods able to produce exopolysaccharide. They accumulated glycine–betaine, as a major osmolyte, with minor components ectoine and glutamate. The strain CRSS biosynthetised α-glucosidase. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol as major components. Ubiquinone with nine repetitive unities (Q9) was the only quinone found and the fatty acid composition was dominated by C18:1 (53%). The G+C content of DNA was 55.0mol% and its phylogenetic position was established by 16S rRNA gene sequencing as a member of the genus Halomonas. For physiological, chemotaxonomic and genetic features (DNA–DNA hybridisation) it is proposed to classify the isolate as a new species for which we propose the name Halomonas alkaliantarctica sp. nov. [Copyright &y& Elsevier]

The haloarchaeon Halorubrum lacusprofundi is among the few polyextremophilic organisms capable of surviving in one of the most extreme aquatic environments on Earth, the Deep Lake of Antarctica (−18 °C to +11.5 °C and 21–28%, w/v salt content). Hence, H. lacusprofundi has been proposed as a model for biotechnology and astrobiology to investigate potential life beyond Earth. To understand the mechanisms that allow proteins to adapt to both salinity and cold, we structurally (including X-ray crystallography and molecular dynamics simulations) and functionally characterized the β-galactosidase from H. lacusprofundi (hla_bga). Recombinant hla_bga (produced in Haloferax volcanii) revealed exceptional stability, tolerating up to 4 M NaCl and up to 20% (v/v) of organic solvents. Despite being cold-adapted, hla_bga was also stable up to 60 °C. Structural analysis showed that hla_bga combined increased surface acidity (associated with halophily) with increased structural flexibility, fine-tuned on a residue level, for sustaining activity at low temperatures. The resulting blend enhanced structural flexibility at low temperatures but also limited protein movements at higher temperatures relative to mesophilic homologs. Collectively, these observations help in understanding the molecular basis of a dual psychrophilic and halophilic adaptation and suggest that such enzymes may be intrinsically stable and functional over an exceptionally large temperature range. [ABSTRACT FROM AUTHOR]