Soluble methane monooxygenase gene clusters from trichloroethylene-degrading Methylomonas sp strains and detection of methanotrophs during in situ bioremediation

The soluble MMO (sMMO) gene clusters from group I methanotrophs were charac terized. An 8.1-kb KpnI fragment from Methylomonas sp. strain KSWIII and a 7.5-kb SalI fragment from Methylomonas sp. strain KSPIII which contained th e sMMO gene clusters were cloned and sequenced. The sequences of these two fragments were almost identical. The sMMO gene clusters in the fragment con sisted of six open reading frames which were 52 to 79% similar to the corre sponding genes of previously described sMMO gene clusters of the group II a nd group X methanotrophs. The phylogenetic analysis of the predicted amino acid sequences of sMMO demonstrated that the sMMOs from these strains were closer to that from M. capsulatus Bath in the group X methanotrophs than to those from Methylosinus trichosporium OB3b and Methylocystis sp. strain hi in the group II methanotrophs. Based on the sequence data of sMMO genes of our strains and other methanotrophs, we designed a new PCR primer to ampli fy sMMO gene fragments of all the known methanotrophs harboring the mmoX ge ne. The primer set was successfully used for detecting methanotrophs in the groundwater of trichloroethylene-contaminated sites during in situ-biostim ulation treatments.