A Novel Transformation of Polychlorinated Biphenyls by Rhodococcus sp. Strain RHA1

Abstract

We have characterized a biphenyl degrader, Rhodococcus sp. strain RHA1. Biphenyl-grown cells of strain RHA1 efficiently transformed 45 components in the 62 major peaks of a polychlorinated biphenyl (PCB) mixture of Kanechlors 200, 300, 400, and 500 within 3 days, which includes mono-to octachlorobiphenyls. Among the intermediate metabolites of PCB transformation, di-and trichlorobenzoic acids were identified. The gradual decrease of these chlorobenzoic acids during incubation indicated that these chlorobenzoic acids would also be degraded by this strain. The effect of the position of chlorine substitution was determined by using PCB mixtures that have chlorine substitutions mainly at either the ortho or the meta position. This strain transformed both types of congeners, and strong PCB transformation activity of RHA1 was indicated. RHA1 accumulated 4-chlorobenzoic acid temporally during the transformation of 4-chlorobiphenyl. The release of most chloride in the course of 2,2-dichlorobiphenyl degradation was observed. These results suggested that RHA1 would break down at least some PCB congeners into smaller molecules to a considerable extent.

Methyl‐β‐cyclodextrin‐enhanced solubilization and aerobic biodegradation of polychlorinated biphenyls in two aged‐contaminated soils

“…It is of interest to note that quite large amounts of biphenyl-growing bacteria bearing bph genes, highly homologous to those of the Grampositive Rhodococcus species, occurred and persisted versus the treatment period in the RAMEB-amended S1 and S2 reactors. This finding is of particular interest as Grampositive bacteria, which are very often the dominating cultivable bacteria in microbial communities of contaminated soils enriched with biphenyl (Wagner-Dobler et al, 1998), have been described as the most effective PCBbiodegrading aerobic bacteria (Asturias et al, 1995;Chung et al, 1994;Focht, 1995;Masai et al, 1997;McKay et al, 1997;Seeger et al 2001;Seto et al, 1995;Wang et al, 1995;Williams et al, 1997;Yamada et al, 1998). These data, taken together, suggest that RAMEB improved the bioremediation of S1 and S2 not only by enhancing the bioavailability of PCBs in the reactors but also by increasing the occurrence of highly specialized aerobic bacteria in the soil solution.…”

Validation of a more sensitive method for using spotted oligonucleotide DNA microarrays for functional genomics studies on bacterial communities

“…LB400 (Bopp, 1986) and Rhodococcus sp. RHA1 (Seto et al ., 1995) and their genetically modified derivatives RHA1(pRHD34) containing the fcbABC operon for 4‐chlorobenzoate (4‐CBA) dechlorination (Rodrigues et al ., 2001) and LB400(pRO41) containing the ohbRABC operon for ortho‐CBA dechlorination (Tsoi et al ., 1999). Wild‐type strains were routinely grown at 30°C in mineral medium K1 (Zaitsev and Karasevich, 1985) , supplemented with biphenyl (1 g l −1 ).…”

The genus Rhodococcus

“…This means that they are persistent in the environment and they are considered to be particularly hazardous. Various PCBs can be degraded by strains of R. rhodochrous, R. globerulus, R. erythropolis and other unclassified rhodococci (Boyle et al 1992;Asturias and Timmis 1993;Maeda et al 1995;Seto et al 1995).…”