UC Marine Council

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 non-growing) bacteria as well as to dead bacteria. For PCP (an ionizing chemical), bacterial growth decreased and death increased as the PCP concentration increased. In sorption experiments, the partition coefficient was affected by (a) active uptake of PCP by living bacteria but not by dead bacteria, (b) death of the living bacteria due to PCP toxicity, and (c) saturation of site specific sorption as the PCP concentration increased. HCB (a non-ionizing chemical) did not affect the growth or death of the bacteria at all HCB concentrations investigated. In sorption experiments, 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 non-ionizing chemical with equilibrium partition coefficient similar to that of HCB) were similar to those for HCB.