GENE-TRANSFER FROM A BACTERIUM INJECTED INTO AN AQUIFER TO AN INDIGENOUS BACTERIUM

Two novel 3-chlorobenzoate-degrading bacteria were previously isolated from an aquifer in which no such bacteria could be enriched prior to the introduction of the 3-chlorobenzoate-degrading strain, Pseudomonas sp. B13. To understand the origin of 3-chlorobenzoate-degrading genes in the two novel isolates, the 16S ribosomal RNA, clcD (dienelactone hydrolase) and clcA (chlorocatechol oxygenase) genes from these bacter ia were amplified and sequenced. The partial 16S rRNA gene sequences a nd REP-PCR patterns showed that these two novel isolates were identica l but differed from strain B13. Phylogenetic analyses revealed that th e novel isolates were closely related to Alcaligenes eutrophus in the beta subclass of the Proteobacteria, whereas strain B13 was related to Pseudomonas aeruginosa and P. mendocina in the gamma subclass of the Proteobacteria. In contrast, the clcD and clcA gene sequences were ide ntical on strain B13 and these two isolates, indicating that the 3-chl orobenzoate-degrading genes were transferred from strain B13 to these isolates. What cannot be established is when this transfer occurred.