A novel benzoate-degrading Rhodococcus strain contains three catA genes with one being transcriptionally active during the growth on benzoate.

The gene encoding catechol 1, 2-dioxygenase (catA) is one of the common biomarkers used for evaluation of microbial degradation of aromatic compounds and bioremediation potentials, whereas the expression of the gene has been little studied. The diversity of the catA genes and their expression pattern in a novel Rhodococcus sp. strain LIN isolated from coastal sediments of the Bohai Sea, China, were investigated. We found that this strain exhibited catechol 1, 2-dioxygenase activity when cultivated with benzoate as the sole carbon source. The catA genes were amplified with degenerate primers and sequenced. Sequence analyses show that the strain has three catA genes which are highly similar to each other (> 97%). However, only one gene was transcribed according to reverse transcription-polymerase chain reaction (RT-PCR) analysis. This indicates that RNA-based approaches could better reflect the diversity and scale of the environmental microbial function than DNA-based ones, when sequencing and quantifying (e.g. quantitative PCR) of the catA gene are employed to assess the environmental pollutions and bioremediations.