In situ growth of the novel SM1 euryarchaeon from a string-of-pearls-like microbial community in its cold biotope,its physical separation and insights into its structure and physiology

Recently, a unique archaeal/bacterial community that grows in a macroscopically visible string-of-pearls-like structure in cold (~10 °C), sulfurous marsh water was discovered. Here, a new technique is described that allows the fast and reliable growth of these string-of-pearls-like microbial communities in larger quantities on polyethylene nets in nature. The microbial net population, estimated to consist of about 10,000 single pearls, can be harvested once a week and the archaeal cells selectively separated by density gradient centrifugation. As in native pearls, the archaeal cell fraction obtained consisted of a single type of coccoid cells only, 0.6 µm in diameter. This novel type of euryarchaea has been tentatively named SM1 euryarchaeon. Electron microscopy and immuno-fluorescence in situ hybridization (immuno-FISH) revealed that about 100 pili-like fibers, up to 3 µm in length, emanate radially from the surface of each cell. The SM1 euryarchaeal cells exhibited a viability of about 90%. The optimal conditions for viability were temperatures between –2 °C and 20 °C, pH 5–9, and low salt conditions; cell viability was independent of oxygen partial pressures. The cultures stained gram-positive, the cell wall was sensitive to SDS, EDTA and Proteinase K treatment. The cells did not exhibit the typical fluorescence for methanogens and did not contain coenzyme F₄₂₀. The G+C-content was 34.5 mol%.     

Complete genome sequence of Halogeometricum borinquense type strain (PR3)

Halogeometricum borinquense Montalvo-Rodríguez et al. 1998 is the type species of the genus, and is of phylogenetic interest because of its distinct location between the halobacterial genera Haloquadratum and Halosarcina. H. borinquense requires extremely high salt (NaCl) concentrations for growth. It can not only grow aerobically but also anaerobically using nitrate as electron acceptor. The strain described in this report is a free-living, motile, pleomorphic, euryarchaeon, which was originally isolated from the solar salterns of Cabo Rojo, Puerto Rico. Here we describe the features of this organism, together with the complete genome sequence, and annotation. This is the first complete genome sequence of the halobacterial genus Halogeometricum, and this 3,944,467 bp long six replicon genome with its 3937 protein-coding and 57 RNA genes is part of the Genomic Encyclopedia of Bacteria and Archaea project.     

Complete genome sequence of Halorhabdus utahensis type strain (AX-2)

Halorhabdus utahensis Wainø et al. 2000 is the type species of the genus, which is of phylogenetic interest because of its location on one of the deepest branches within the very extensive euryarchaeal family Halobacteriaceae. H. utahensis is a free-living, motile, rod shaped to pleomorphic, Gram-negative archaeon, which was originally isolated from a sediment sample collected from the southern arm of Great Salt Lake, Utah, USA. When grown on appropriate media, H. utahensis can form polyhydroxybutyrate (PHB). Here we describe the features of this organism, together with the complete genome sequence, and annotation. This is the first complete genome sequence of the a member of halobacterial genus Halorhabdus, and the 3,116,795 bp long single replicon genome with its 3027 protein-coding and 48 RNA genes is part of the Genomic Encyclopedia of Bacteria and Archaea project.