RESUMO
A novel hydrogenotrophic methanogen, strain HHBT, was isolated from a deep-sea hydrothermal vent chimney sample collected from Beebe Vent Field at the Mid-Cayman Spreading Center, Caribbean Sea. The cells were non-motile regular to irregular cocci possessing several flagella. The novel isolate grew at 60-80 °C, pH 5.0-7.4 and with 1-4â% of NaCl (w/v). The isolate utilized H2/CO2 as the only substrates for growth and methane production. The results of phylogenetic analyses of both 16S rRNA and mcrA gene sequences and comparative genome analysis indicated that HHBT represented a member of the order Methanococcales, and was closely related to the members of the genera Methanothermococcus and Methanotorris. The most closely related species were Methanothermococcus okinawensis IH1T and Methanotorris igneus Kol 5T in comparison of 16S rRNA gene sequences (each with 93â% identity), and Methanotorris formicicus Mc-S-70T in the case of deduced amino acid sequence similarity of mcrA genes (92â% similarity). The ANI and AAI values between HHBT and the members of the genera Methanothermococcus and Methanotorris were 69-72â% and 66-70â%, respectively. Although many of the morphological and physiological characteristics were quite similar between HHBT and the species of the genera Methanothermococcus and Methanotorris, they were distinguishable by the differences in susceptibility to antibiotics, formate utilization, growth temperature and NaCl ranges. On the basis of these phenotypic, phylogenetic and genomic properties, we propose that strain HHBT represents a novel species, of a novel genus, Methanofervidicoccus abyssi gen. nov., sp. nov. The type strain is HHBT (=JCM 32161T=DSM 105918T).
Assuntos
Fontes Hidrotermais/microbiologia , Methanococcaceae/classificação , Filogenia , Região do Caribe , DNA Arqueal/genética , Genes Arqueais , Methanococcaceae/isolamento & purificação , RNA Ribossômico 16S/genética , Água do Mar , Análise de Sequência de DNA , TemperaturaRESUMO
The protein derived from the Methanocaldococcus jannaschii MJ0458 gene is annotated as a δ-1-pyrroline 5-carboxylate synthetase and is predicted to be related to aspartokinase and uridylate kinase. Analysis of the predicted protein sequence indicated that it is a unique kinase with few similarities to either uridylate or adenylate kinase. Here, we report that the MJ0458 gene product is a second type of archaeal adenylate kinase, AdkB. This enzyme is different from the established archaeal-specific adenylate kinase in both sequence and predicted tertiary structure.
Assuntos
Adenilato Quinase/metabolismo , Methanococcaceae/enzimologia , Núcleosídeo-Fosfato Quinase/metabolismo , Monofosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Adenilato Quinase/química , Archaea/enzimologia , Methanococcaceae/classificação , Núcleosídeo-Fosfato Quinase/química , Fosforilação , Filogenia , Especificidade por SubstratoRESUMO
Purine biosynthesis requires 10 enzymatic steps in higher organisms, while prokaryotes require an additional enzyme for step 6. In most organisms steps 9 and 10 are catalyzed by the purH gene product, a bifunctional enzyme with both 5-formaminoimidazole-4-carboxamide ribonucleotide (FAICAR) synthase and inosine monophosphate (IMP) cyclohydrolase activity. Recently it was discovered that Archaea utilize different enzymes to catalyze steps 9 and 10. An ATP-dependent FAICAR synthetase is encoded by the purP gene, and IMP cyclohydrolase is encoded by the purO gene. We have determined the X-ray crystal structures of FAICAR synthetase from Methanocaldococcus jannaschii complexed with various ligands, including the tertiary substrate complex and product complex. The enzyme belongs to the ATP grasp superfamily and is predicted to use a formyl phosphate intermediate formed by an ATP-dependent phosphorylation. In addition, we have determined the structures of a PurP orthologue from Pyrococcus furiosus, which is functionally unclassified, in three crystal forms. With approximately 50% sequence identity, P. furiosus PurP is structurally homologous to M. jannaschii PurP. A phylogenetic analysis was performed to explore the possible role of this functionally unclassified PurP.
Assuntos
Proteínas Arqueais/metabolismo , Methanococcaceae/metabolismo , Fosforribosilaminoimidazolcarboxamida Formiltransferase/metabolismo , Ribonucleotídeos/biossíntese , Proteínas Arqueais/química , Proteínas Arqueais/genética , Sítios de Ligação , Cristalografia por Raios X , Methanococcaceae/classificação , Methanococcaceae/genética , Modelos Moleculares , Fosforribosilaminoimidazolcarboxamida Formiltransferase/química , Fosforribosilaminoimidazolcarboxamida Formiltransferase/genética , Filogenia , Estrutura Secundária de Proteína , Estrutura Terciária de ProteínaRESUMO
A novel thermophilic, methane-producing archaeon was isolated from a deep-sea hydrothermal vent chimney at the Iheya Ridge, in the Okinawa Trough, Japan. The cells were highly motile, irregular cocci, with a polar bundle of flagella. Growth was observed between 40 and 75 degrees C (optimum 60-65 degrees C; 30 min doubling time) and between pH 4.5 and 8.5 (optimum pH 6.7). The isolate was a strictly anaerobic autotroph capable of using hydrogen and carbon dioxide as sole sources of energy and carbon. Formate can serve as an alternative energy source. The G+C content of the genomic DNA was 33.5 mol%. Phylogenetic analysis based on 16S rDNA sequences and DNA-DNA hybridization analysis indicated that the isolate was closely related to members of the genera Methanococcus and Methanothermococcus. This isolate, however, could be differentiated from the previously described species of these genera on the basis of its physiological and molecular properties. The name Methanothermococcus okinawensis sp. nov is proposed, with the type strain IH1T (=JCM 11175T=DSM 14208T).