Various strains of Escherichia coli were shown to be capable of utilizing methyl phosphonic acid (Pn) as a sole phosphorus source with resulting methane formation. The efficiency of this process depends on the age and concentration of culture cells. Aeration was an important factor regulating Pn degradation: anaerobic conditions were more favourable for the process. For effective Pn degradation, cells need a long (72 h) period of adaptation to Pn. Adapted cells are able to utilize Pn with an order of efficiency higher than the initial cell culture. Adapted cells contain additional proteins, probably associated with Pn degradation. in different cell compartments and maintain this ability when placed onto fresh media even containing orthophosphate. Adapted cells are probably the best source of C-P lyase for its isolation and study.