Methanotrophic bacteria constitute a ubiquitous group of microorganisms playing an important role in the biogeochemical carbon cycle and in control of global warming through natural reduction of methane emission. These bacteria share the unique ability of using methane as a sole carbon and energy source and have been found in a great variety of habitats. Phylogenetically, known methanotrophs constitute a rather limited group and have so far only been affiliated with the Proteobacteria. Here, we report the isolation and initial characterization of a nonproteobacterial obligately methanotrophic bacterium. The isolate, designated Kam1, was recovered from an acidic hot spring in Kamchatka, Russia, and is more thermoacidophilic than any other known methanotroph, with optimal growth at Ϸ55°C and pH 3.5. Kam1 is only distantly related to all previously known methanotrophs and belongs to the Verrucomicrobia lineage of evolution. Genes for methane monooxygenases, essential for initiation of methane oxidation, could not be detected by using standard primers in PCR amplification and Southern blot analysis, suggesting the presence of a different methane oxidation enzyme. Kam1 also lacks the well developed intracellular membrane systems typical for other methanotrophs. The isolate represents a previously unrecognized biological methane sink, and, due to its unusual phylogenetic affiliation, it will shed important light on the origin, evolution, and diversity of biological methane oxidation and on the adaptation of this process to extreme habitats. Furthermore, Kam1 will add to our knowledge of the metabolic traits and biogeochemical roles of the widespread but poorly understood Verrucomicrobia phylum.extremophile ͉ methanotroph

The platelet‐derived growth factor (PDGF) family was for more than 25 years assumed to consist of only PDGF‐A and ‐B. The discovery of the novel family members PDGF‐C and PDGF‐D triggered a search for novel activities and complementary fine tuning between the members of this family of growth factors. Since the expansion of the PDGF family, more than 60 publications on the novel PDGF‐C and PDGF‐D have been presented, highlighting similarities and differences to the classical PDGFs. In this paper we review the published data on the PDGF family covering structural (gene and protein) similarities and differences among all four family members, with special focus on PDGF‐C and PDGF‐D expression and functions. Little information on the protein structures of PDGF‐C and ‐D is currently available, but the PDGF‐C protein may be structurally more similar to VEGF‐A than to PDGF‐B. PDGF‐C contributes to normal development of the heart, ear, central nervous system (CNS), and kidney, while PDGF‐D is active in the development of the kidney, eye and brain. In adults, PDGF‐C is active in the kidney and the central nervous system. PDGF‐D also plays a role in the lung and in periodontal mineralization. PDGF‐C is expressed in Ewing family sarcoma and PDGF‐D is linked to lung, prostate and ovarian cancers. Both PDGF‐C and ‐D play a role in progressive renal disease, glioblastoma/medulloblastoma and fibrosis in several organs.

Archaea have been detected recently as a major and often dominant component of the microbial communities performing ammonia oxidation in terrestrial and marine environments. In a molecular survey of archaeal ammonia monooxygenase (AMO) genes in terrestrial hot springs of Iceland and Kamchatka, the amoA gene encoding the alpha-subunit of AMO was detected in a total of 14 hot springs out of the 22 investigated. Most of these amoA-positive hot springs had temperatures between 82 and 97 degrees C and pH range between 2.5 and 7. In phylogenetic analyses, these amoA genes formed three independent lineages within the known sequence clusters of marine or soil origin. Furthermore, in situ gross nitrification rates in Icelandic hot springs were estimated by the pool dilution technique directly on site. At temperatures above 80 degrees C, between 56 and 159 mumol NO(3)(-) L(-1) mud per day was produced. Furthermore, addition of ammonium to the hot spring samples before incubation yielded a more than twofold higher potential nitrification rate, indicating that the process was limited by ammonia supply. Our data provide evidence for an active role of archaea in nitrification of hot springs in a wide range of pH values and at a high temperature.

Archaea often live in extreme, harsh environments such as acidic hot springs and hypersaline waters. To date, only two icosahedrally symmetric, membrane-containing archaeal viruses, SH1 and Sulfolobus turreted icosahedral virus (STIV), have been described in detail. We report the sequence and three-dimensional structure of a third such virus isolated from a hyperthermoacidophilic crenarchaeon, Sulfolobus strain G4ST-2. Characterization of this new isolate revealed it to be similar to STIV on the levels of genome and structural organization. The genome organization indicates that these two viruses have diverged from a common ancestor. Interestingly, the prominent surface turrets of the two viruses are strikingly different. By sequencing and mass spectrometry, we mapped several large insertions and deletions in the known structural proteins that could account for these differences and showed that both viruses can infect the same host. A combination of genomic and proteomic analyses revealed important new insights into the structural organization of these viruses and added to our limited knowledge of archaeal virus life cycles and host-cell interactions.

Korarchaeota constitute a recently proposed and little characterized kingdom of Archaea that might have diverged before the lineages of Crenarchaeota and Euryarchaeota split. To assess the diversity, distribution and abundance of Korarchaeota, we analysed 19 terrestrial hot springs in Hveragerdi and Krysuvik, Iceland, and in Kamchatka, Russia. The springs were 70-97 1C with pH 2.5-6.5. Out of 19 springs, 12 tested positive for Korarchaeota with specific primers. A Korarchaeota 16S rDNA library was made from each of these. From the 301 clones sequenced, 87 unique sequences were obtained from Iceland and 33 from Kamchatka. The similarity between Kamchatkan and Icelandic 16S rDNA sequences and that of Candidatus Korarchaeum cryptofilum was p93.5%. Phylogenetic analyses revealed a clear separation between sequences retrieved from terrestrial and marine habitats. Within the terrestrial sequences, four clusters could be recognized showing a geographic distribution with surprisingly low diversity. Furthermore, the abundance of Korarchaeota 16S rDNA in the 12 environmental samples was analysed using quantitative PCR (qPCR), showing that Korarchaeota represent only a minor fraction of the microbial community in hot springs; however, in some cases they constitute up to 7% of all Archaea. Taxonomic profiling of an Icelandic Korarchaeota-positive habitat revealed an Aquificales-dominated community. In fact, Aquificales were dominating or present in high numbers in all 12 positive sites. Chemical analyses of three Korarchaeota-positive hot springs showed their occurrence in variable water chemistry. Our data provide new information on Korarchaeota habitats and shed light on their abundance, diversity, distribution and coexisting organisms.