f Methanobacterium oryzae sp. nov., a novel methanogenic rod isolated from a Philippines ricefield.

A rod (0.3-0.4 micron x 3-10 microns) to filamentous (up to 40 microns) non-motile methanogenic bacterium, designated strain FPiT (T = type strain), was isolated from ricefield soil in the Philippines. The strain uses H2 + CO2 or formate for growth and produces CH4. Optimum growth temperature is 40 degrees C; no growth is observed at 15 degrees C or 45 degrees C. Optimum pH for growth is 7; no growth is observed at pH 5.5 or 9.0. Strain FPiT is halotolerant and grows at NaCl concentrations of 0-25 g l-1. The G + C content of its DNA is 31 mol%. Based on 16S rRNA gene sequence analysis, the isolate was identified as a new species of the genus Methanobacterium: Methanobacterium oryzae sp. nov. The type strain is FPiT (= DSM 11106T).