Springer Science and Business Media LLC

The genome of the halophilic archaeon Halobacterium salinarum encodes the high-affinity ATP-dependent K+ uptake system Kdp. Previous studies have shown that the genes coding for the KdpFABC complex are arranged in a kdpFABCQ gene cluster together with an additional gene kdpQ. In bacteria, expression of the kdpFABC genes is generally regulated by the dedicated sensor kinase/response regulator pair KdpD/KdpE, which are absent in H. salinarum. Surprisingly, H. salinarum expresses the kdp genes in a manner which is strikingly similar to Escherichia coli. In this study, we show that the halobacterial kdpFABCQ genes constitute an operon and that kdpFABCQ expression is subject to a complex regulatory mechanism involving a negative transcriptional regulator and is further modulated via a so far unknown mechanism. We describe how the regulation of kdp gene expression is facilitated in H. salinarum in contrast to its bacterial counterparts. Whereas the Kdp system fulfils the same core function as an ATP-driven K+ uptake system in both archaea and bacteria, the different mechanisms involved in the regulation of gene expression appear to have evolved separately, possibly reflecting a different physiological role of ATP-driven K+ uptake in halophilic archaea.

Snow is a unique microhabitat, despite being a harsh environment, multiple life forms have adapted to survive in it. While algae, bacteria and fungi are dominant microorganisms in Antarctic snow, little is known about other organisms that may be present in this habitat. We used metabarcoding to investigate DNA sequence diversity of non-fungal eukaryotes present in snow obtained from six different sites across the Maritime Antarctica. A total of 20 taxa were assigned to obtained sequences, representing five Kingdoms (Chromista, Protozoa, Viridiplantae and Metazoa) and four phyla (Ciliophora, Cercozoa, Chlorophyta and Cnidaria). The highest diversity indices were detected in Trinity Peninsula followed by Robert Island, Arctowski Peninsula, Deception Island, King George Island and Snow Island. The most abundant assignments were to Trebouxiophyceae, followed by Chlamydomonas nivalis and Chlamidomonadales. No taxa were detected at all sites. Three potentially new records for Antarctica were detected: two Ciliophora (Aspidisca magna and Stokesia sp.) and the green algae Trebouxia potteri. Our data suggested that similarities found between the sites may be more related with snow physicochemical properties rather than geographic proximity or latitude. This study provides new insights into the diversity and distribution of eukaryotic organisms in Antarctic snow.

Genes potentially coding for three distinct [NiFe] hydrogenases are present in the genome of Aquifex aeolicus. We have demonstrated that all three hydrogenases are expressed under standard growth conditions of the organism. Two hydrogenases were further purified to homogeneity. A periplasmically oriented hydrogenase was obtained in two forms, i.e., as a soluble enzyme containing only the two essential subunits and as a detergent-solubilized complex additionally containing a membrane-integral b-type cytochrome. The second hydrogenase purified was identified as a soluble cytoplasmic enzyme. The isolated enzymes were characterized with respect to biochemical/biophysical parameters, activity, thermostability, and substrate specificity. The phylogenetic positioning of all three hydrogenases was analyzed. A model for the metabolic roles of the three enzymes is proposed on the basis of the obtained results.

Permafrost in China mainly located in high-altitude areas. It represents a unique and suitable ecological niche that can be colonized by abundant microbes. Permafrost microbial community varies across geographically separated locations in China, and some lineages are novel and possible endemic. Besides, Chinese permafrost is a reservoir of functional microbial groups involved in key biogeochemical cycling processes. In future, more work is necessary to determine if these phylogenetic groups detected by DNA-based methods are part of the viable microbial community, and their functional roles and how they potentially respond to climate change. This review summaries recent studies describing microbial biodiversity found in permafrost and associated environments in China, and provides a framework for better understanding the microbial ecology of permafrost.

Three Gram-positive bacterial strains, 7-3, 255-15 and 190-11, previously isolated from Siberian permafrost, were characterized and taxonomically classified. These microorganisms are rod-shaped, facultative aerobic, motile with peritrichous flagella and their growth ranges are from −2.5 to 40°C. The chemotaxonomic markers indicated that the three strains belong to the genus Exiguobacterium. Their peptidoglycan type was A3α L-Lys-Gly. The predominant menaquinone detected in all three strains was MK7. The polar lipids present were phosphatidyl-glycerol, diphosphatidyl-glycerol and phosphatidyl-ethanolamine. The major fatty acids were iso-C13:0, anteiso-C13:0, iso-C15:0, C16:0 and iso-C17:0. Phylogenetic analysis based on 16S rRNA and six diverse genes, gyrB (gyrase subunit B), rpoB (DNA-directed RNA polymerase beta subunit), recA (homologous recombination), csp (cold shock protein), hsp70 (ClassI-heat shock protein—chaperonin) and citC (isocitrate dehydrogenase), indicated that the strains were closely related to Exiguobacterium undae (DSM 14481T) and Exiguobacterium antarcticum (DSM 14480T). On the basis of the phenotypic characteristics, phylogenetic data and DNA–DNA reassociation data, strain 190-11 was classified as E. undae, while the other two isolates, 7-3 and 255-15, comprise a novel species, for which the name Exiguobacterium sibiricum sp. nov. is proposed.

Permafrost represents a unique ecosystem that has allowed the prolonged survival of certain bacterial lineages at subzero temperatures. To better understand the permafrost microbial community, it is important to identify isolation protocols that optimize the recovery of genetically diverse bacterial lineages. We have investigated the impact of different low-temperature isolation protocols on recovery of aerobic bacteria from northeast Siberian permafrost of variable geologic origin and frozen for 5000 to 3 million years. Low-nutrient media enhanced the quantitative recovery of bacteria, whereas the isolation of diverse morphotypes was maximized on rich media. Cold enrichments done directly in natural, undisturbed permafrost led not only to recovery of increased numbers of bacteria but also to isolation of genotypes not recovered by means of liquid low-temperature enrichments. On the other hand, direct plating and growth at 4°C also led to recovery of diverse genotypes, some of which were not recovered following enrichment. Strains recovered from different permafrost samples were predominantly oligotrophic and non-spore-forming but were otherwise variable from each other in terms of a number of bacteriological characteristics. Our data suggest that a combination of isolation protocols from different permafrost samples should be used to establish a culture-based survey of the different bacterial lineages in permafrost.