Effects of 2,2′,5,5′-tetrachlorobiphenyl and biphenyl on cell membranes of Ralstonia eutropha H850

Abstract

The effects of 2,2P,5,5P-tetrachlorobiphenyl (TeCB), a PCB congener, and biphenyl on the cytoplasmic membranes of Ralstonia eutropha H850 were investigated by measuring fluorescence polarization using 1,6-diphenyl-1,3,5-hexatriene (DPH) as the probe, and determining the cellular fatty acid compositions. TeCB significantly affected the membrane of R. eutropha H850 cells grown on fructose by decreasing DPH fluorescence polarization. In contrast, the membrane of cells grown on biphenyl showed a considerably less significant effect of TeCB on membrane polarization than in fructose-grown cells. An increase in the ratio of total saturated to unsaturated fatty acids in cells grown on biphenyl suggested less of a fluidizing effect of TeCB on membranes in those cells. When biphenyl-grown cells were transferred back to a fructose medium, they required 25 generations for the membrane polarization and fatty acid compositions of these cells to revert back to those of the initial fructose-grown cells. The re-adaptation to a change in temperature required only five generations to return to normal. These results show that biphenyl affects cells in more ways than simply fluidizing the cytoplasmic membrane. ß : S 0 3 7 8 -1 0 9 7 ( 0 1 ) 0 0 1 9 5 -1

“ Dehalococcoides ” sp. Strain CBDB1 Extensively Dechlorinates the Commercial Polychlorinated Biphenyl Mixture Aroclor 1260

“…All of those experiments used high PCB concentrations, 20 to 500 g/ml, that were known to be dechlorinated in sediment microcosms or in sediment-free mixed cultures derived from PCB-contaminated sites. PCBs, like other hydrophobic compounds, can adsorb to and partition into cell membranes causing cell stress as manifested in changes in membrane fluidity, decreased cell surface area, and separation of membrane layers (16,25,30). At high PCB-to-cell ratios these effects would presumably be maximal and might be toxic.…”

Coping with Polychlorinated Biphenyl (PCB) Toxicity: Physiological and Genome-Wide Responses of Burkholderia xenovorans LB400 to PCB-Mediated Stress

“…Indeed recent studies of PCB-tolerant LB400 (13)(14)(15) suggest that cell systems other than the biphenyl pathway contribute to the efficient degradation of biphenyl and PCBs. Although the biphenyl pathway has been extensively studied, the role of auxiliary mechanisms, which may provide tolerance to PCBs, has been lightly investigated, and information on the biological effects of PCBs (25) and their degradation products to bacteria (10, 21) is scarce.…”

“…As PCBs have been insinuated to impair microbial growth (25,42), viability (10), and degradation (7,23,44,47,48), successful remediation should also consider the physiological and genetic responses limiting or overcoming these toxic effects. In this study, we investigate physiological and genomewide cell responses and defenses against the toxicity posed by PCBs.…”

Changes in Membrane Fluidity and Fatty Acid Composition ofPseudomonas putidaCN-T19 in Response to Toluene

“…Membrane ‰uidity was investigated by measuring the ‰uorescence polarization of the probe 1,6-diphenyl-1,3,5-hexatriene (DPH, Molecular Probes, Eugene, OR, USA) inserted into the membranes with the method as described previously. 12) Brie‰y, cells grown on LB with or without toluene were harvested as described above, and resuspended in the same buŠer to give an optical density of 0.4 at 610 nm (OD600). To assess eŠects of toluene on the DPH ‰uorescence polarization in vitro, toluene was added to cell suspension before DPH probe was added.…”

“…When the phase transition temperature was determined by estimating midpoint of temperature, 3 mM toluene lowered the temperature from approximately 24 to 209 C. DPH partitions within the membrane hydrophobic core, where it provides information on the ‰uid state of this region. 12,13) Therefore, decrease in polarization ratios by toluene suggested that toluene had a ‰uidizing eŠect on the hydrophobic core region of cell membranes. Toluene had less ‰uidizing eŠect on the membranes of P. putida CN-T19 cells grown with toluene (Fig.…”