Sorption of hydrophobic organic chemicals to bacteria.

The toxicity and time-dependent sorption of three hydrophobic organic chemicals to Rhodococcus rhodochrous bacteria were investigated. In experiments, environmentally relevant concentrations of pentachlorophenol (PCP), hexachlorobenzene (HCB), and dichlorobiphenyl (DPCB) were applied to living (both growing and nongrowing) bacteria as well as to dead bacteria. For PCP (an ionizing chemical), bacterial growth decreased, and bacterial death increased, as the PCP concentration increased. In sorption experiments with PCP, the partition coefficient was affected by the active uptake of PCP by living but not by dead bacteria, by the death of the living bacteria because of PCP toxicity, and by saturation of site-specific sorption as the PCP concentration increased. Hexachlorobenzene (a nonionizing chemical) did not affect bacterial growth or death at all HCB concentrations investigated. In sorption experiments with HCB, the partition coefficient depended on the rate of bacterial growth relative to the sorption rate. The sorption rate depended on the state of bacterial aggregation, and this changed with time. Results for DPCB (a nonionizing chemical with an equilibrium partition coefficient similar to that of HCB) were similar to those for HCB.