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Scientific Research and Essays Vol. 2 (7),
244-250, July 2007
ISSN 1992-2248
© 2007 Academic Journals
Full Length
Research Paper
Toxicity of phenolic compounds to
oxidoreductases of Acinetobacter species isolated from a tropical
soil
J. C. Okolo*, C. O. Nweke, R. N. Nwabueze, C. U. Dike and
C. E. Nwanyanwu
Department of Microbiology, Federal University of Technology, P. M.
B.1526, Owerri, Nigeria.
*Corresponding author. E-mail:
chiookolo@yahoo.com
Accepted
15 June, 2007 |
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The effects of 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and
4-bromophenol on the acti-vities of periplasmic nitrate reductase and
dehydrogenase enzymes of Acinetobacter sp. iso-lated from a
tropical soil were assessed via reduction of nitrate and
2,3,5-triphenyltetrazoluim chloride, respectively. There were
significant differences in the response of dehydrogenase enz-yme but not periplasmic nitrate reductase to the various compounds. However, at
different concentrations, the phenolic compounds had significant effects
on periplasmic nitrate reductase but not dehydrogenase activity.
Estimations of the degree of inhibition/stimulation of both enzyme
activities showed a significant dose-dependent response.
2,4-Dinitrophenol showed decreasing progressive stimulation of
dehydrogenase enzyme with increasing concentration (40 – 200 mg/l) while
2-nitrophenol, 4-nitrophenol and 4-bromophenol showed increasing
progres-sive inhibition of both enzyme activities. The IC50 of
the phenolic compounds to the periplasmic nitrate reductase activity
were comparable (33.46 – 44.75 mg/l) but lower than those for the
dehydrogenase activity (>200 mg/l). This suggested greater sensitivity
of periplasmic nitrate reductase than dehydrogenase enzyme to the
phenolic compounds. This study suggested that the toxic effects of
chemicals on specific microbiological activities are better studied
using the appropriate enzymes involved rather than the dehydrogenase
activity.
Key words:
Acinetobacter
sp.,
dehydrogenase, periplasmic nitrate reductase, phenolic compounds. |
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