Rapid assay for screening and characterizing microorganisms for the ability to degrade polychlorinated biphenyls

Abstract

We designed a rapid assay that assesses the polychlorinated biphenyl (PCB)-degradative competence and congener specificity of aerobic microorganisms, identifies strains capable of degrading highly chlorinated biphenyls, and distinguishes among those that degrade PCBs by alternative pathways. Prior attempts to assay PCB-degradative competence by measuring disappearance of Aroclors (commercial PCB mixtures) have frequently produced false-positive findings because of volatilization, adsorption, or absorption losses. Furthermore, these assays have generally left the chemical nature of the competence obscure because of incomplete gas chromatographic resolution and uncertain identification of Aroclor peaks. We avoided these problems by using defined mixtures of PCB congeners and by adopting incubation and extraction methods that prevent physical loss of PCBs. Our assay mixtures include PCB congeners ranging from dichloro- to hexachlorobiphenyls and representing various structural classes, e.g., congeners chlorinated on a single ring (2,3-dichlorobiphenyl), blocked at 2,3 sites (2,5,2'5'-tetrachlorobiphenyl), blocked at 3,4 sites (4,4'-dichlorobiphenyl), and lacking adjacent unchlorinated sites (2,4,5,2',4',5'-hexachlorobiphenyl). The PCB-degrative ability of microorganisms is assessed by packed-column gas chromatographic analysis of these defined congener mixtures following 24-h incubation with resting cells. When tested with 25 environmental isolates, this assay revealed a broad range of PCB-degradative competence, highlighted differences in congener specificity and in the extent of degradation of individual congeners, predicted degradative competence on commercial PCBs, and (iv) identified strains with superior PCB-degradative ability.

Evidence of aerobic utilization of di‐ortho‐substituted trichlorobiphenyls as growth substrates by Pseudomonas sp. SA‐6 and Ralstonia sp. SA‐4

“…It is noteworthy that the triCB congeners utilized by SA-4 and SA-6 are poorly degraded co-metabolically by many of the bacterial strains previously described by others (Furukawa, 1982;Bedard et al, 1986;Maltseva et al, 1999). The initial characterization of the isolates described in the present report demonstrates that aerobic biodegradation of triCBs in the absence of other carbon substrates is possible.…”

Reduction of Aryl Hydrocarbon Receptor-Mediated Activity of Polychlorinated Biphenyl Mixtures Due to Anaerobic Microbial Dechlorination

“…Anaerobic microbial reductive dechlorination is expected to be more effective in decreasing the AhR-mediated toxicity of PCB mixtures than aerobic microbial metabolism of PCBs. This is because the congeners most responsible for AhRmediated toxicity (e.g., 3,3Ј,4,4Ј,5-CB) are readily dechlorinated from meta and/or para positions but are resistant to aerobic microbial degradation [24]. Fig.…”

Insights into the genomic plasticity of Pseudomonas putida KF715, a strain with unique biphenyl‐utilizing activity and genome instability properties

“…A number of biphenyl-utilizing pseudomonad strains have been isolated from various environments worldwide (Bedard et al, 1986;Furukawa and Fujihara, 2008). These strains can cometabolize certain polychlorinated biphenyl (PCB) congeners to chlorobenzoates, allowing the biochemical and genetic bases of the microbial degradation of PCBs to be studied (Furukawa et al, 2004;Pieper et al, 2004).…”