Effects of Polychlorinated Biphenyls on Macromolecular Synthesis by a Heterotrophic Marine Bacterium

Abstract

Growth rates and final cell yields of a polychlorinated biphenyl (PCB)-sensitive pseudomonad isolated from the open ocean were reduced in a dose-dependent manner by 10 to 100 ,ug of Aroclor 1254 per liter, a commercial mixture of PCB isomers added to its culture medium. Effects on growth rates were detected within 1 h (approximately one doubling time) of treatment. By 4 h posttreatment, the amounts of deoxyribonucleic acid and ribonucleic acid per cell in exponentially growing populations treated with sublethal doses of Aroclor were detectably lower than in appropriate controls. Corresponding cell protein values were slightly higher than in controls. Selective degradation of cell proteins or nucleic acids was not detected in cells whose growth was totally suppressed for 4 h by PCBs. Cells whose growth rate was inhibited 20 to 50% by Aroclor synthesized protein at normal rates for periods in excess of 5 h from the time the chlorinated hydrocarbons were added. In contrast, rates per cell of adenine uptake and adenine incorporation into deoxyribonucleic acid and total nucleic acids by the cells treated with PCBs were significantly lower than in control cells. Intracellular adenine pools of cells whose growth was inhibited to 20% of the control rate by PCBs were 30% smaller and appeared to require a longer interval to equilibrate than those of untreated cells. This may indicate impaired transport and/or efflux of this nucleic acid precursor through the membrane of affected cells. Inhibition of nucleic acid synthesis in this sensitive bacterium by PCBs could explain the observed inhibitory effects of the chlorinated hydrocarbons on its growth.

Effects of Polychlorinated Biphenyls on Growth and Respiration of Heterotrophic Marine Bacteria

“…The apparent uncoupling of transport and oxidation of selected substrates from growth in the bacteria studied suggested the possibility that PCBs might interfere with the biosynthetic rather than catabolic capacity of sensitive bacteria. Studies of the effect of Aroclor 1254 on macromolecular synthesis in strain 41 are reported in the accompanying manuscript (1).…”

Ecotoxicological effects of creosote contamination on benthic microbial populations in an estuarine environment†

“…Forest Products Laboratory, 1974). Evidence of the in vitro toxicity of individual PAHs and other toxic substances to bacterioplankton has been demonstrated (Calder and Lader, 1976;Blakemore, 1978;Sayler et al, 1982a). However, extrapolation of these data to predict the responses of natural benthic bacterial communities to similar toxicants is questionable.…”