Phylogenetic analysis of trichloroethylene-degrading bacteria newly isolated from soil polluted with this contaminant

Five methanotrophs (strains 18-2, EB1, KSWIII, KSPIII and KSPIII) and three aromatic compound oxidizers (strains KP22, KP24 and KT1) were isolated fro m the natural held polluted with trichloroethylene (TCE). Phylogenetic anal ysis based on 16S rRNA gene sequence suggested that all of the isolates bel onged to the class Proteobacteria. Two of the methanotrophic isolates, stra ins 18-2 and EB1, were closely related to Methylocystis sp. strain M in the a subclass of Proteobacteria with sequence similarities of 98.2-98.4%, whi le strains KSWIII, KSPIII and KSPII were akin to Methylomonas methanica in the gamma subclass of Proteobacteria with sequence similarities of 97.8-98. 1%. The aromatic compounds oxidizers, strains KP22, KP24 and KT1, were assi gned to the beta subclass of Proteobacteria, and classified as Bordetella s p. (97.2-97.8% sequence similarity to species of the genus Bordetella), Bur kholderia cepacia (99.2%) and Ralstonia eutropha (99.4%), respectively. All isolates degraded TCE when cells were grown with the appropriate substrate , i.e., methane, phenol or toluene. Detailed kinetic analyses of their TCE degradation revealed that the rates of degradation (k1) among the isolates were 10-36 ml of TCE/mg of dry cell weight/h, and the transformation capaci ties (Tc) were 0.01-0.13 mg of TCE/mg of dry cell weight.