The Microbial Community of Poultry Farm Waste and Its Role in Hydrogen Sulfide Production

Microbiology - The microbiota of chicken litter remains largely unexplored, despite its leading role in the formation of volatile odorants and unpleasant odors. One of the main components of the...     

Metagenomic Analysis of the Microbial Community in the Underground Coal Fire Area (Kemerovo Region,Russia) Revealed Predominance of Thermophilic Members of the Phyla Deinococcus-Thermus,Aquificae, and Firmicutes

Microbiology - Underground burning of coal seams accompanied by release of gases leads to development of local thermal ecosystems. We investigated the microbial community of the ground heated to...     

A Novel Plasmid pALWVS1.4 from Acinetobacter lwoffii Strain VS15, Carrying the Chloramphenicol Resistance Gene

Microbiology - Sequencing and analysis of the genome of the chloramphenicol-resistant strain Acinetobacter lwoffii VS15, isolated from permafrost, revealed a circular plasmid 11 964 bp in...     

Mitochondrial Genomes of Flor Yeast Strains Are Characterized by Low Genetic Variability

Russian Journal of Genetics - High concentrations of ethanol and oxidative stress can cause a mutagenic effect on mitochondrial genomes (mtDNAs) of flor yeasts. We performed a comparative analysis...     

Nicotinamidase from the thermophilic archaeon Acidilobus saccharovorans: Structural and functional characteristics

Nicotinamidase is involved in the maintenance of NAD⁺ homeostasis and in the NAD⁺ salvage pathway of most prokaryotes, and it is considered as a possible drug target. The gene (ASAC_0847) encoding a hypothetical nicotinamidase has been found in the genome of the thermophilic archaeon Acidilobus saccharovorans. The product of this gene, NA_As0847, has been expressed in Escherichia coli, isolated, and characterized as a Fe²⁺-containing nicotinamidase (k _cat/K _m = 427 mM^?1·sec^?1)/pyrazinamidase (k _cat/K _m = 331 mM^?1·sec^?1). NA_As0847 is a homodimer with molecular mass 46.4 kDa. The enzyme has high thermostability (T_1/2 (60°C) = 180 min, T_1/2 (80°C) = 35 min) and thermophilicity (T_opt = 90°C, E_a = 30.2 ± 1.0 kJ/mol) and broad pH interval of activity, with the optimum at pH 7.5. Special features of NA_As084 are the presence of Fe²⁺ instead of Zn²⁺ in the active site of the enzyme and inhibition of the enzyme activity by Zn²⁺ at micromolar concentrations. Analysis of the amino acid sequence revealed a new motif of the metal-binding site (DXHXXXDXXEXXXWXXH) for homological archaeal nicotinamidases.     

The Genome Sequence of the Crenarchaeon Acidilobus saccharovorans Supports a New Order,Acidilobales, and Suggests an Important Ecological Role in Terrestrial Acidic Hot Springs

Acidilobus saccharovorans is an anaerobic, organotrophic, thermoacidophilic crenarchaeon isolated from a terrestrial hot spring. We report the complete genome sequence of A. saccharovorans, which has permitted the prediction of genes for Embden-Meyerhof and Entner-Doudoroff pathways and genes associated with the oxidative tricarboxylic acid cycle. The electron transfer chain is branched with two sites of proton translocation and is linked to the reduction of elemental sulfur and thiosulfate. The genomic data suggest an important role of the order Acidilobales in thermoacidophilic ecosystems whereby its members can perform a complete oxidation of organic substrates, closing the anaerobic carbon cycle.Acidophilic microorganisms are widely dispersed in natural acidic environments, including volcanic hot springs, and are, in the majority, aerobes (14). However, such anoxic, high-temperature, acidic environments are inhabited by metabolically versatile anaerobic thermoacidophiles of the archaeal phylum Crenarchaeota. Lithoautotrophic thermoacidophiles oxidize molecular hydrogen in the course of elemental sulfur (S⁰) respiration. Organotrophs couple the oxidation of organic substrates to the reduction of S⁰ or thiosulfate. They all belong to the genus Acidilobus in the family Acidilobaceae and to the genus Caldisphaera in the family Caldisphaeraceae (4, 13, 22, 24). Acidilobaceae and Caldisphaeraceae form the crenarchaeal order Acidilobales (24). Acidilobus saccharovorans was isolated from an acidic hot spring of Uzon Caldera, Kamchatka, Russia (24). It is an obligately anaerobic acidophile with a range of growth from pH 2.5 to 5.8 (optimum at pH 3.5 to 4) and a temperature range from 60 to 90°C (optimum at 80 to 85°C). It utilizes a wide range of proteinaceous and carbohydrate substrates and cannot grow lithoautotrophically on H₂ and CO₂ (24). S⁰ and thiosulfate stimulate growth and are reduced to H₂S. Protons cannot serve as electron acceptors, since no H₂ is produced during growth in the absence of S⁰ (24). Genomic sequences of aerobic, thermoacidophilic euryarchaea Thermoplasma acidophilum (26) and Picrophilus torridus (8) give an insight into the thermoacidophilic survival strategy. However, no genomes of obligately anaerobic, thermoacidophilic archaea were available until now. Here we present the genome of A. saccharovorans and show that it encodes numerous hydrolytic enzymes and metabolic pathways necessary for the utilization and complete mineralization of organic substrates in its natural habitat, acidic hot springs.     

The Geoglobus acetivorans Genome: Fe(III) Reduction,Acetate Utilization,Autotrophic Growth,and Degradation of Aromatic Compounds in a Hyperthermophilic Archaeon

Geoglobus acetivorans is a hyperthermophilic anaerobic euryarchaeon of the order Archaeoglobales isolated from deep-sea hydrothermal vents. A unique physiological feature of the members of the genus Geoglobus is their obligate dependence on Fe(III) reduction, which plays an important role in the geochemistry of hydrothermal systems. The features of this organism and its complete 1,860,815-bp genome sequence are described in this report. Genome analysis revealed pathways enabling oxidation of molecular hydrogen, proteinaceous substrates, fatty acids, aromatic compounds, n-alkanes, and organic acids, including acetate, through anaerobic respiration linked to Fe(III) reduction. Consistent with the inability of G. acetivorans to grow on carbohydrates, the modified Embden-Meyerhof pathway encoded by the genome is incomplete. Autotrophic CO₂ fixation is enabled by the Wood-Ljungdahl pathway. Reduction of insoluble poorly crystalline Fe(III) oxide depends on the transfer of electrons from the quinone pool to multiheme c-type cytochromes exposed on the cell surface. Direct contact of the cells and Fe(III) oxide particles could be facilitated by pilus-like appendages. Genome analysis indicated the presence of metabolic pathways for anaerobic degradation of aromatic compounds and n-alkanes, although an ability of G. acetivorans to grow on these substrates was not observed in laboratory experiments. Overall, our results suggest that Geoglobus species could play an important role in microbial communities of deep-sea hydrothermal vents as lithoautotrophic producers. An additional role as decomposers would close the biogeochemical cycle of carbon through complete mineralization of various organic compounds via Fe(III) respiration.