EFFECTS OF THE HERBICIDE, BUTACHLOR, ON
NITROGEN FIXATION IN PHOTOTROPHIC
NONSULFUR BACTERIA |
Kyung Mi Lee1, Jaisoo Kim2, and Hyun Soon Lee1† |
1Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Korea 2Department of Life Science, Kyonggi University, Suwon 443-760, Korea |
Corresponding Author:
Hyun Soon Lee ,Tel: +82-31-249-9648, Fax: +82-31-249-9139, Email: jkimtamu@kyonggi.ac.kr |
Received: January 8, 2007; Accepted: September 9, 2007. |
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ABSTRACT |
In an effort to identify possible microbes for seeking bioagents for remediation of herbicidecontaminated
soils, seven species of phototrophic nonsulfur bacteria (Rhodobacter capsulatus and sphaeroides,
Rhodospirillum rubrum, Rhodopseudomonas acidophila, blastica and viridis, Rhodomicrobium vannielii) were
grown in the presence of the herbicide, butachlor, and bacterial growth rates and nitrogen fixation were
measured with different carbon sources. Under general conditions, all species showed 17-53% reductions in
growth rate following butachlor treatment. Under nitrogen-fixing conditions, Rb. capsulatus and Rs. rubrum
showed 1-4% increases in the growth rates and 2-10% increases in nitrogen-fixing abilities, while the other
5 species showed decreases of 17-47% and 17-85%, respectively. The finding that Rp. acidophila, Rp. blastica,
Rp. viridis and Rm. vannielii showed stronger inhibitions of nitrogenase activity seems to indicate that
species in genera Rhodobacter and Rhodospirillum are less influenced by butachlor than those in Rhodopseudomonas
and Rhodomicrobium in terms of nitrogen-fixing ability. Overall, nitrogenase activity was closely
correlated with both growth rate and glutamine synthetase activity (representing nitrogen metabolism). When
the carbon sources were compared, pyruvate (three carbons) was best for all species in terms of growth rate
and nitrogen fixation, with malate (four carbons) showing intermediate values and ribose (five carbons)
showing the lowest; these trends did not change in response to butachlor treatment. We verified that each
of the 7 species had a plasmid (12.2~23.5 Kb). We found that all 7 species could use butachlor as a sole
carbon source and 3 species were controlled by plasmid-born genes, but it is doubtful whether plasmid-born
genes were responsible to nitrogen fixation. |
Keywords:
Butachlor | Herbicide | Nitrogen fixation | Plasmid | Purple nonsulfur bacteria |
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