Methanogens: reevaluation of a unique biological group.

Gliding motility, ultrastructure and nutrition of two newly isolated filamentous sulfate-reducing bacteria, strains 5ac10 and 4be13, were investigated. The filaments were always attached to surfaces. Growth was supported by addition of insoluble aluminium phosphate or agar as substrata for gliding movement. Electron microscopy of ultrathin sections revealed cell walls characteristic of Gramnegative bacteria; the undulated structure of the outer membrane may pertain to the translocation mechanism. Intracytoplasmic membranes were present. Acetate, higher fatty acids, succinate or fumarate served as electron donors and carbon sources. Strain 5ac10 grew also with lactate, but not with benzoate that was used only by strain 4be13. Strain 5ac10 was able to grow slowly on H2 plus CO2 or formate in the presence of sulfate without additional organic carbon source. The capacity of complete oxidation was shown by stoichiometric measurements with acetate plus sulfate. Both strains contained b- and c-type cytochromes. Desulfoviridin was detected only in strain 5ac10. The two filamentous gliding sulfate reducers are described as new species of a new genus, Desulfonema limicola and Desulfonema magnum.

Studies on dissimilatory sulfate-reducing bacteria that decompose fatty acids

Taxonomic, Phylogenetic, and Ecological Diversity of Methanogenic Archaea

A new extremely thermophilic methane-producing bacterium was isolated from a submarine hydrothermal vent sample collected by a research team from the Woods Hole Oceanographic Institution using the manned submersible ALVIN. The sample was obtained from the base of a “white smoker” chimney on the East Pacific Rise at 20° 50′ N latitude and 109° 06′ W longitude at a depth of 2600 m. The isolate was a motile irregular coccus with an osmotically fragile cell wall and a complex flagellar system. In defined medium with 80% H2 and 20% CO2, the isolate had a doubling time of 26 min at 85° C. The pH range for growth was 5.2 to 7.0 with an optimum near 6.0. NaCl was required for growth with an optimum of 2 to 3% (w/v). The mol % G+C was 31%. In cell-free extracts, methane formation from methylcoenzyme M was temperature-dependent, and H2 or formate served as electron donors. Methane formation from H2 and CO2 occurred at a much lower rate. Oligonucleotide cataloging of the 16S ribosomal RNA established the isolate as a new species of the genus Methanococcus and the name Methanococcus jannaschii is proposed. The isolation of M. jannaschii from a submarine hydrothermal vent provides additional evidence for biogenic production of CH4 from these deep-sea environments.

Methanococcus jannaschii sp. nov., an extremely thermophilic methanogen from a submarine hydrothermal vent

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(01)01701-2.pdf

Challenge of psychrophilic anaerobic wastewater treatment

A new genus of marine methanogenic bacteria and two species within this genus are described.Methanogenium is the proposed genus andMethanogenium cariaci the type species. Cells of the type species are Gram-negative, peritrichously flagellated, irregular cocci with a periodic wall surface pattern. Colonies formed by these bacteria are yellow, circular and umbonate with entire edges. The DNA base composition is 52 mol% guanine plus cytosine. Formate or hydrogen and carbon dioxide serve as substrates for growth. Cells ofMethanogenium marisnigri are of similar shape but smaller diameter thanM. cariaci. The colonies ofM. marisnigri are convex, and the DNA base composition is 61 mol % G+C. Formate or hydrogen and carbon dioxide are growth substrates. Sodium chloride is required for growth of both methanogens.

Methanogenium, a new genus of marine methanogenic bacteria, and characterization ofMethanogenium cariaci sp. nov. andMethanogenium marisnigri sp. nov.

The fine structure of the cell envelope, of membrane systems and of cytoplasmic inclusions of Gram-negative aerobic hydrogen bacteria has been studied. The results have been tabulated, and three main groups could be recognized: Group 1: Alcaligenes eutrophus, A.paradoxus, A.ruhlandii, Pseudomonas facilis, P.flava, P.pseudoflava, P.palleronii, and Aquaspirillum autotrophicum; Group 2: "Corynebacterium" autotrophicum and strains MA 2 and SA 35; Group 3: Paracoccus denitrificans. Special structures related to the chemoautotrophic way of life of the hydrogen bacteria were not observed.

Micromorphology of Gram-negative hydrogen bacteria. II. Cell envelope, membranes, and cytoplasmic inclusions.

The cell morphology, the arrangement and fine structure of flagella and the piliation of the following Gram-negative aerobic hydrogen bacteria have been studied: Alcaligenes eutrophus, Alcaligenes paradoxus, Alcaligenes ruhlandii, Pseudomonas flava, Pseudomonas pseudoflava, Pseudomonas palleronii, Pseudomonas facilis, Aquaspirillum autotrophicum, Paracoccus denitrificans, Corynebacterium autotrophicum, and strains MA 2 and SA 35. The identity of the bacteria was examined by their substrate spectra and type of flagellation. Three types of flagellar fine structure were differentiated. The presence of pili was noted in strains of Alcaligenes paradoxus, Pseudomonas flava, P.pseudoflava, P.palleronii, and P.facilis.

Micromorphology of Gram-negative hydrogen bacteria. I. Cell morphology and flagellation.

Summary
Polysheaths were spontaneously formed inside cells of the hydrogen bacterium Alcaligenes eutrophus H 16. These particles are long tube-like structures of 24 nm diam. belonging to the phage tail-like defective bacteriophages (Lotz, 1976). In mid log-phase fermenter-grown cells, polysheaths were observed in about 20% of all cells sectioned. Evidence is provided for an inhibition of cell fission by polysheaths. Polysheaths were isolated by differential centrifugation and precipitation techniques using PEG and antibodies. The morphology of polysheaths was investigated electron microscopically by negative staining, ultrathin sectioning and metal shadowing. A surface lattice of the polysheath was derived from light optical diffraction data. The particles were also characterized by their biochemical and biophysical features: mol. wt. of the subunit determined by SDS-gel electrophoresis (58000), amino acid composition, isoelectric point (4.4), u.v. absorbance spectrum indicating the absence of nucleic acid, buoyant density (1.258), and stability against denaturants and proteolytic enzymes.

Anna Walther-Mauruschat

Papers

Methanogenium, a new genus of marine methanogenic bacteria, and characterization ofMethanogenium cariaci sp. nov. andMethanogenium marisnigri sp. nov.

Micromorphology of Gram-negative hydrogen bacteria. II. Cell envelope, membranes, and cytoplasmic inclusions.

Micromorphology of Gram-negative hydrogen bacteria. I. Cell morphology and flagellation.

Isolation and characterization of polysheaths, phage tail-like defective bacteriophages of Alcaligenes eutrophus H 16.