Ultrastructural changes in Synechococcus leopoliensis produced by cadmium as influenced by pH.
Item
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Title
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Ultrastructural changes in Synechococcus leopoliensis produced by cadmium as influenced by pH.
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Identifier
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AAI9405591
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identifier
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9405591
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Creator
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Tang, Ming.
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Contributor
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Adviser: Thomas E. Jensen
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Date
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1993
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Microbiology | Biology, Cell | Biology, Ecology
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Abstract
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Synechococcus leopoliensis was used as a representative of fresh-water cyanobacteria to study the toxic effect of the heavy metal, cadmium, on their growth and survival. Statistical analyses of the morphometric data showed that more cellular inclusions were changed in relative volumes in Cd{dollar}\sp{lcub}2+{rcub}{dollar} exposed cells at pH 9 than 5.5, both than at 7.2.;In cells exposed to 0.8 {dollar}\mu{dollar}M Cd{dollar}\sp{lcub}2+{rcub}{dollar} at pH5.5, electron dense and spherical inclusions in polyhedral bodies occurred at a frequency of 43% in contrast to 0 in the control cells. Elemental analysis of these inclusions using the scanning transmission mode of the TEM in conjunction with a PGT energy dispersive X-ray spectrometer (EDX) demonstrated that the inclusions inside polyhedral bodies contained P and Ca and were in fact PPB's.;Cd was detected mainly in the cytoplasmic and cell wall sectors with the EDX analysis, when S. leopoliensis cells were exposed to Cd{dollar}\sp{lcub}2+{rcub}{dollar} at 80 {dollar}\mu{dollar}M for 4 hours. As the exposure Cd{dollar}\sp{lcub}2+{rcub}{dollar} concentration increased to a higher concentration, such as 600 {dollar}\mu{dollar}M, most Cd was accumulated into the PPB's. Although the cell surface might be able to control the penetration of the Cd{dollar}\sp{lcub}2+{rcub}{dollar} at low concentrations, Cd was taken up intracellularly as the exposure concentration increased. The phosphorus rich PPB's in the cytoplasm attracted most of the Cd. The same pattern of uptake observed in the cells exposed to 600 {dollar}\mu{dollar}M Cd{dollar}\sp{lcub}2+{rcub}{dollar} at 4{dollar}\sp\circ{dollar}C in the dark suggested that the Cd uptake in the first 4 hrs is mostly by passive diffusion.;Gel electrophoresis of cell proteins revealed differences in the protein band patterns of exposed cells from those of control cells. The significant enhancement of proteins in the sediment fractions (cell envelope and membrane) might suggest that the Cd{dollar}\sp{lcub}2+{rcub}{dollar} effect could be one of the protein denaturation or disassembly of the proteinaceous structures in cells. (Abstract shortened by UMI.).
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
