Physiological and cytological responses of the marine diatom Skeletonema costatum to 2,4-dichlorophenol.
Physiological and cytological responses of the marine diatom, Skeletonema costatum, to 2,4-dichlorophenol (2,4-DCP) were investigated after exposing algal cultures to 1-6 mg x l(-1) of 2,4-DCP for 96 h. Growth rate of the diatom was significantly reduced by 2,4-DCP at and above 3.0 mg x l(-1) while other biological parameters such as photosynthetic and respiration rates, carotenoid and protein content, ATP level and adenylate energy charge were unaffected. Exposure to 6.0 mg x l(-1) 2,4-DCP for 96 h resulted in the total lipid content being increased to 304%, while the RNA/DNA ratio was reduced to 31% of the control values. A parallel study by transmission electron microscopy further confirmed the increase in cellular lipid content, as evidenced by the accumulation of lipid droplets within diatom cells. A slight increase in carbohydrate (+37.8%) and decrease in chlorophyll a (-20.4%) and total chlorophyll c (-14.4%) were also found at 6.0 mg x l(-1) 2,4-DCP. Although 2,4-DCP is known to uncouple oxidative phosphorylation, our results show that energy production was not significantly inhibited at sublethal concentrations of 2,4-DCP. The observed growth inhibition in S. costatum caused by 2,4-DCP was associated with an increase in energy storage and inhibition of protein synthesis, as indicated by a reduction in RNA/DNA ratio.
Yang
Shao
S
Department of Biology and Chemistry and Centre for Coastal Pollution and Conservation, City University of Hong Kong, Tat Chee Avenue, Kowloon, Special Administrative Region, Hong Kong, China.
Wu
Rudolf S S
RS
Kong
Richard Y C
RY
D000222:Adaptation, Physiological; D000255:Adenosine Triphosphate / Q000032:analysis; D000871:Anthelmintics / Q000009:adverse effects*; D002733:Chlorophenols / Q000009:adverse effects*; D004247:DNA / Q000032:analysis; D017377:Diatoms / Q000502:physiology*; D004734:Energy Metabolism / Q000187:drug effects*; D010788:Photosynthesis / Q000187:drug effects; D011157:Population Dynamics; D014176:Protein Biosynthesis; D012313:RNA / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000009:adverse effects*
D000871:Anthelmintics; D002733:Chlorophenols; D014874:Water Pollutants, Chemical; D012313:RNA; D000255:Adenosine Triphosphate; D004247:DNA; C004762:2,4-dichlorophenol