Isolation, characterization, and nitrification potential of a methylotroph and two heterotrophic bacteria from a consortium showing methane-dependent nitrification

A methanotrophic nitrifying consortium was previously obtained from a humisol which showed CH4-dependent nitrification. Although the methanotroph could not be obtained in pure culture, three other members of the consortium have been isolated: An obligately methylotrophic Methylobacillus (Is-1) which grows only on CH3OH and does not nitrify; a Pseudomonas (Is-2) which grows on Is-1 culture filtrate and produces NO2−, NO3− and N2O from NH2OH, and NO3− from NO2−; and a second Pseudomonas (Is-3) which produces NO3− from NH4+ or NO2−, and N2O from NH2OH. A model is proposed for the trophic relations and nitrogen transformations in the consortium which may apply to some natural systems.