Effects of polychlorinated biphenyls on macromolecular synthesis by a heterotrophic marine bacterium

Effects of polychlorinated biphenyls on growth and respiration of heterotrophic marine bacteria

A number of marine bacterial isolates from both near-shore and open-ocean environments were tested for growth inhibition with exposure to low concentrations (1 to 100 mug/liter) of Aroclor 1254, a commercial mixture of polychlorinated biphenyls (PCBs). Of over 17 bacterial cultures tested, growth of only two open-ocean isolates, one a pseudomonad and the other a tetrad-forming coccus, was consistently inhibited by Aroclor at concentrations as low as 10 mug/liter (10 ppb). Growth inhibition was dose dependent over a concentration range of 10 to 100 mug/liter. The effects upon division rates and final cell yields of each bacterial isolate were greatest when PCBs were added to cultures with low cell densities or with lower specific growth rates. The pseudomonad also had reduced carotenoid levels and an altered filamentous morphology with Aroclor present at a concentration of 10 mug/liter, or more. The effects noted were reversible for at least 18 h after initial exposure. Concentrations of Aroclor in excess of those needed to stop growth had no detectable effect upon the respiration rate of cells of either culture. This suggests that the reduced division rates observed were not due to inability of PCB-treated cells to transport or catabolize the carbohydrate or amino acid substrates tested.

The cytology and biochemistry of pesticide microbiology

Widespread use of pesticides has no doubt benefited human beings in one way or another. However, their side effects on various organisms, including nontarget organisms, are largely overlooked. In the recent past, several studies have been done to assess the effects of pesticides on nontarget organisms, including microorganisms. Although pesticide effects on growth parameters of microorganisms have been extensively reviewed, little attention has been paid regarding their cytological and biochemical aspects. Therefore, the present work is mainly concerned with the cytological and biochemical aspects of pesticide microbiology. The effects of pesticides on photosynthesis, respiration, proteins, and nucleic acids are reviewed. Attention is also paid to their effects on cell morphology and morphogenesis and their effect on cell constituents.

Effects of four aromatic organic pollutants on microbial glucose metabolism and thymidine incorporation in marine sediments

The metabolism of D-[U-14C]glucose and the incorporation of [methyl-3H]thymidine by aerobic and anaerobic marine sediment microbes exposed to 1 to 1,000 ppm anthracene, naphthalene, p,p'-dichlorodiphenyltrichloroethane, and pentachlorophenol were examined. Cell-specific rates of [14C]glucose metabolism averaged 1.7 X 10(-21) and 0.5 X 10(-21) mol/min per cell for aerobic and anaerobic sediment slurries, respectively; [3H]thymidine incorporation rates averaged 43 X 10(-24) and 9 X 10(-24) mol/min per cell for aerobic and anaerobic slurries, respectively. Aerobic sediments exposed to three of the organic pollutants for 2 to 7 days showed recovery of both activities. Anaerobic sediments showed little recovery after 2 days of pre-exposure to the pollutants. We conclude that (i) anaerobic sediments are more sensitive than aerobic sediments to pollutant additions; (ii) [3H]thymidine incorporation is more sensitive to pollutant additions than is [14C]glucose metabolism; and (iii) the toxicity of the pollutants increased in the following order: anthracene, p,p'-dichlorodiphenyltrichloroethane, naphthalene, and pentachlorophenol.

Effect of DDT on cell population growth, cell division, and DNA synthesis in Stylonychia notophora (Stokes)

The effect of DDT on growth and DNA synthesis in Stylonychia notophora was investigated. DDT at a concentration of one ppm did not alter the cell population growth and the morphology of the organisms. However, 50 and 100 ppm DDT inhibited growth and cell division. Continuous treatment of the organisms with 100 ppm DDT produced several nuclear abnormalities. Cells treated with 100 ppm DDT in G1 did not enter S-phase while DNA synthesis was blocked in those cells treated in S-phase.

Comparative effects of Aroclor 1254 (polychlorinated biphenyls) and phenanthrene on glucose uptake by freshwater microbial populations

The effects of polychlorinated biphenyl (PCB) and phenanthrene stress on glucose uptake by natural microbial populations were examined by the heterotrophic potential technique. Temporal and spatial distributions in glucose uptake velocities were examined for natural samples as well as PCB- and phenanthrene-stressed samples. Statistical analysis indicated significant variability among the various samples. It was demonstrated that the environmental variables contributed significantly to the variability in uptake kinetics. Although general trends indicated a PCB-induced stimulation in uptake velocities, these trends were in part masked by sample variability. Data analysis indicated no statistically significant PCB or phenanthrene effect on either total glucose uptake velocities or the proportion of 14CO2 evolved, as compared to natural unstressed samples.