The submarine ikaite columns located in the Ikka Fjord in Southern Greenland represent a unique, permanently cold (less than 6°C) and alkaline (above pH 10) environment and are home to a microbial community adapted to these extreme conditions. The bacterial and archaeal community inhabiting the ikaite columns and surrounding fjord was characterised by high-throughput pyrosequencing of 16S rRNA genes. Analysis of the ikaite community structure revealed the presence of a diverse bacterial community, both in the column interior and at the surface, and very few archaea. A clear difference in overall taxonomic composition was observed between column interior and surface. Whereas the surface, and in particular newly formed ikaite material, was primarily dominated by Cyanobacteria and phototrophic Proteobacteria, the column interior was dominated by Proteobacteria and putative anaerobic representatives of the Firmicutes and Bacteroidetes. The results suggest a stratification of the ikaite columns similar to that of classical soda lakes, with a light-exposed surface inhabited by primary producers and an anoxic subsurface. This was further supported by identification of major taxonomic groups with close relatives in soda lake environments, including members of the genera Rhodobaca, Dethiobacter, Thioalkalivibrio and Tindallia, as well as very abundant groups related to uncharacterised environmental sequences originally isolated from Mono Lake in California.

Bacteria belonging to the Streptomyces genus are known to produce several taste-and-odour compounds (TOCs), but knowledge on the abundance of streptomycetes in drinking water reservoirs and other aquatic environments is scarce. In this study, quantitative real-time polymerase chain reaction (qPCR) was applied, for the first time, to determine densities of streptomycetes in a river, at a weir and in two reservoirs in subtropical Australia. The PCR approach was optimized with respect to (a) collection of streptomycetes in water, (b) extraction of DNA, and (c) a procedure to correct for inhibition of PCR amplification by natural substances in the water. Mean densities of Streptomyces cells at the study sites varied from 225 to 45,650 cells L À1 . The highest density occurred in bottom water (8.5 m deep) of one of the reservoirs, while densities in the Brisbane River varied between 260 and 7,950 cells L À1 . At the weir site, seasonal variation in abundance in winter and spring in surface water (mean densities of 430-13,550 cells L À1 ) did not correlate with total bacterial abundance (0.9-3.5 × 10 9 cells L À1 ). The qPCR approach shows that quantitation of streptomycetes in fresh water can be successfully achieved and may prove valuable in predicting TOC episodes in aquatic systems used for drinking water supplies.

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SummaryProteases active at low temperature or high pH are used in many commercial applications, including the detergent, food and feed industries, and bacteria specifically adapted to these conditions are a potential source of novel proteases. Environments combining these two extremes are very rare, but offer the promise of proteases ideally suited to work at both high pH and low temperature. In this report, bacteria from two cold and alkaline environments, the ikaite columns in Greenland and alkaline ponds in the McMurdo Dry Valley region, Antarctica, were screened for extracellular protease activity. Two isolates, Arsukibacterium ikkense from Greenland and a related strain, Arsukibacterium sp. MJ3, from Antarctica, were further characterized with respect to protease production. Genome sequencing identified a range of potential extracellular proteases including a number of putative secreted subtilisins. An extensive liquid chromatography–tandem mass spectrometry analysis of proteins secreted by A. ikkense identified six subtilisin‐like proteases as abundant components of the exoproteome in addition to other peptidases potentially involved in complete degradation of extracellular protein. Screening of Arsukibacterium genome libraries in Escherichia coli identified two orthologous secreted subtilisins active at pH 10 and 20°C, which were also present in the A. ikkense exoproteome. Recombinant production of both proteases confirmed the observed activity.

Arsukibacterium ikkense GCM72T and a close relative, Arsukibacterium sp. MJ3, were isolated from two cold and alkaline environments as producers of extracellular proteolytic enzymes active at high pH and low temperature. This report describes the two draft genome sequences, which may serve as sources of future industrial enzymes.