Effect of surfactant solubilization on biodegradation of polychlorinated biphenyl congeners by Pseudomonas LB400

A variety of commercial surfactants were tested to determine their effect on polychlorinated biphenyl (PCB) transformation by Pseudomonas LB400. Initial tests determined that most surfactants were fully or partially able to solubilize the PCB congeners 2,5,2'-chlorobiphenyl (CBP), 2,4,2',4'-CBP, 2,3,5,2',5'-CBP and 2,4,5,2',4',5'-CBP, at concentrations above the surfactants' critical micelle concentration (CMC). Surfactants were also found to have no negative effect on bacterial survival, as cell numbers were the same or higher after incubation in the presence of surfactants than after incubation without surfactants. A comparison of the extent of biotransformation of single PCB congeners by the bacterium revealed that, at surfactant concentrations above the CMC, the presence of an anionic surfactant promoted while nonionic surfactants inhibited PCB transformation, compared to a control with no surfactant. The rates of transformation of PCB congeners were also higher in the presence of the anionic surfactant compared to the control. The inhibitory effects of a nonionic surfactant, Igepal CO-630 at a concentration above its CMC, on transformation of 2,4,5,2',5'-CBP could be eliminated by diluting the surfactant/PCB solution to a concentration close to the surfactant CMC.

Production of metabolites from chlorobiphenyls by resting cells ofPseudomonasstrain LB400 after growth on different carbon sources

Cells of Pseudomonas strain LB400, grown on biphenyl, glucose, or glycerol, transformed polychlorinated biphenyl (PCB) congeners into chlorobenzoic acid (CBA) metabolites. Transformation of the PCB congeners, 2,3-chlorobiphenyl (CBP), 2,2'-CBP, 2,5,4'-CBP, and 2,4,2',4'-CBP, produced the metabolites, 2,3-CBA, 2-CBA, 4-CBA, and 2,4-CBA, respectively. Rates and extents of PCB transformation and metabolite formation were highest with biphenyl-grown cells. Intermediate rates of metabolite production were observed with glycerol-grown cells, and lowest rates of production were found with glucose-grown cells. Regardless of carbon source, the rate of degradation of congeners was faster than the rate of production of CBAs. Relative rates of PCB transformation and metabolite production from different congeners with cells grown on a particular substrate followed the same general order, 2,3-CBA (from 2,3-CBP) > 2-CBA (from 2,2'-CBP) > 4-CBA (from 2,5,4'-CBP) > 2,4-CBA (from 2,4,2',4'-CBP). Pseudomonas strain LB400 appeared unable to grow on any of the chlorobenzoic acids. However, Pseudomonas strain LB400 cells grown on biphenyl appeared capable of degrading 2-CBA and 2,3-CBA but not 4-CBA nor 2,4-CBA. Cells grown on glycerol appeared unable to metabolize any CBAs.Key words: polychlorinated biphenyls, metabolites, Pseudomonas LB400.

Comparison of the degradation patterns of polychlorinated biphenyl congeners in Aroclors by Pseudomonas strain LB400 after growth on various carbon sources

Resting cells of Pseudomonas strain LB400, grown on biphenyl, transformed 80, 50 and 17% of Aroclor 1242, 1254, and 1260, respectively. Resting cells grown on glucose or glycerol also transformed these polychlorinated biphenyl (PCB) mixtures to the extent of 60, 35, and 9% for Aroclors 1242, 1254, and 1260, respectively. Time courses of the transformation of the separated individual congeners in the Aroclors were plotted and used to determine the transformation rate constants (k). By analysis of the rate constants, it was concluded that the order of degradation of the different congeners in an Aroclor were similar regardless of the growth substrate. In general, k values for the conversion of a particular congener were lower for cells grown on glucose or glycerol compared with cells grown on biphenyl. Generally, k values for the transformation of the same congener in different Aroclors were not the same: rate constants had highest values for the congener in Aroclor 1242 and lowest values in Aroclor 1260. The data allowed congeners to be grouped according to their relative rates of degradation. The ratio of k values for transformation of individual congeners in Aroclors by cells grown on biphenyl and glucose were not constant.

Studies on the transformation of selected polychlorinated biphenyl congeners by Pseudomonas strain LB 400

Resting cells of Pseudomonas strain LB400 are known to transform polychlorinated biphenyls (PCBs) when the cells are previously grown on biphenyl. In this study, PCB transformation was also observed in resting cells grown on other substrates such as glucose and glycerol. The presence of PCB congeners in the growth medium increased the lag phase for the growth of cells on a biphenyl substrate but not on a glycerol substrate. Supplementation of the degradation medium with biphenyl dramatically decreased the rate of PCB congener transformation, while the presence of glycerol or glucose had little or no effect on PCB transformation rates. Removal rates with biphenyl-grown cells in the standard degradation medium for 2,4,2′,4′-tetrachlorobiphenyl, 2,4,5,2′,5′-pentachlorobiphenyl, and 2,3-dichlorobiphenyl were 1.06, 1.66, and 224 μmol/(L∙h), respectively. Relative rates of transformation of 2,3-dichlorobiphenyl by biphenyl-, glucose-, and glycerol-grown cells were 100:36:36 and were similar to the relative rates of transformation of 2,4,5,2′,5′-pentachlorobiphenyl (100:33:42). The presence of PCBs adversely affected cell viability of biphenyl-grown cells over a 48-h incubation period and may explain the decline observed in PCB conversion capacity over the same incubation period. A major objective of this study was to investigate the significance of using biphenyl as the carbon source for growth of Pseudomonas strain LB400 cells capable of PCB transformation. Our findings indicate that, whereas higher rates of transformation of PCBs are observed with biphenyl-grown cells, cells grown on other carbon sources retain PCB-transforming enzymes. In addition, it has been demonstrated that biphenyl inhibits transformation of PCBs by the organism, whereas glycerol or glucose does not.Key words: Pseudomonas strain LB400, polychlorinated biphenyls, degradation, biphenyl.

Evaluation of the role of exogenous pathogens on the incidence of embryo loss during early pregnancy in mice

The mating of CBA/j female mice (H2k) by DBA/2j male mice (H2d) typically results in an elevated incidence of spontaneous embryo loss thus providing an ideal genetically controlled laboratory model for the study of the factors causing early embryo loss during pregnancy. There is now considerable data on the cells and factors involved in fetal resorption but little is known about the events which activate this process. While the activation of the maternal response to the fetal implant could have endogenous or genetic origins, a role for exogenous factors including microbial pathogens could also be involved. In order to investigate these possibilities, the reproductive success of CBA/j female x DBA/2j male matings in a conventional animal care facility were compared with matings in a specific pathogen free (SPF) animal facility. All animals housed under these conditions were routinely screened by immunoassay and culture, for the presence of a number of viral and bacterial pathogens of mice. The incidence of spontaneous embryo loss in specific pathogen free CBA female mice mated by DBA and other male strains was found to be virtually identical to that of CBA female mice infected with multiple viral pathogens and housed under otherwise identical conditions (non-SPF). However, the numbers of implantation per pregnancy was significantly greater in an SPF facility. Therefore, exposure of mating mice to exogenous viral and bacterial pathogens did not appear to alter the overall incidence of spontaneous embryo resorption. It was concluded that the immunomodulatory effects of infection by common murine pathogens neither augmented nor reduced post-implantation embryo losses.