Isolation and characterization of a methanogenic bacterium from mangrove sediments

A methanogenic bacterium was enriched with trimethylamine and isolated from mangrove sediments. The isolate was a non-spore-forming regular to slightly irregular coccus (0.4-1 mm in diameter). The isolate required sodium chloride for growth with maximal methanogenesis at 420 mM NaCl at 30 degrees C. The optimal growth temperature was 30-35 degrees C with maximal methane production at 30 degrees C. The maximum growth rate was between pH 6.6 and 7.2 with maximum methane production at pH 6.8. The growth requirement of sulfide was 10-15 mM with maximum methane production at 10 mM at 30 degrees C. Mono-, di-, and trimethylamine or methanol were substrates for the methanogen; sodium acetate and H-2:CO2 were not. The DNA base content is consistent with the type descriptions of Methanoccoides methylutens, a methylotrophic methanogen isolated from submarine sediments. The isolate was found to utilize methylamines that are found in mangroves without having to compete with sulfate-reducing bacteria for H-2.