This study describes the characterization and naming of a new genus of methanogenic bacteria isolated from sewage sludge. The organism, designated Methanospirillum hungatii, was isolated and characterized by Ferry, Smith, and Wolfe. The bacteria form distinctive light yellow colonies with regular striations spaced two cell lengths apart. Cells are gram-negative curved rods measuring 7.4 by 0.5 micrometers that typically occur in filaments up to 100 micrometers long. Electron microscopy revealed polar flagella and a striated cell surface. The DNA base composition is 45 mol% guanine plus cytosine. The organism is an obligate anaerobe that uses formate or hydrogen with carbon dioxide as substrates for methane production and growth, but cannot utilize acetate, pyruvate, methanol, ethanol, or benzoate. The type strain JF1 has been deposited in the American Type Culture Collection. The genus name Methanospirillum reflects the organism's spiral morphology, and the species name hungatii honors R.E. Hungate.

Key findings

• Methanospirillum hungatii is a new genus and species of methanogenic bacterium with distinctive spiral morphology and uniquely striated colonies
• The organism is gram-negative, forms filaments with polar flagella, and has a DNA G+C content of 45 mol%
• M. hungatii utilizes only formate or hydrogen-carbon dioxide as substrates for methane production, rejecting acetate, pyruvate, methanol, ethanol, and benzoate
• The organism is an extreme anaerobe showing complete oxygen sensitivity and grows optimally at 30-37°C and pH 6.6-7.4
• Type strain JF1 represents this new species and has been deposited as ATCC 27890