Effect of organic and inorganic nitrogenous compounds on RDX degradation and cytochrome P-450 expression in <Emphasis Type="Italic">Rhodococcus</Emphasis> strain YH1 |
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Authors: | Ali Nejidat Limor Kafka Yoram Tekoah Zeev Ronen |
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Institution: | (1) Department of Environmental Hydrology & Microbiology, Zuckerberg Institute for Water Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer, 84990, Israel;(2) Department of Biotechnology Engineering, Faculty of Engineering and Center for Glycobiology, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel |
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Abstract: | We hypothesized that biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)—a widely used explosive contaminating
soil and groundwater—by Rhodococcus strain YH1 is controlled by the presence of external nitrogen sources. This strain is capable of degrading RDX while using
it as sole nitrogen source under aerobic conditions. Both inorganic and organic nitrogen sources were found to have a profound
impact on RDX-biodegradation activity. This effect was tested in growing and resting cells of strain YH1. Nitrate and nitrite
delayed the onset of RDX degradation by strain YH1, while ammonium inhibited it almost completely. In addition, 2,4,6-trinitrotoluene
(TNT) inhibited RDX degradation and growth of strain YH1. On the other hand, tetrahydrophthalamide did not influence biodegradation
or growth. Growth on RDX induced the expression of a cytochrome P-450 enzyme that is suggested to be involved in the first
step in the aerobic pathway of RDX degradation, as identified by SDS-PAGE analysis. Ammonium and nitrite strongly repressed
cytochrome P-450 expression. Our findings suggest that effective RDX bioremediation by strain YH1 requires the design of a
treatment scheme that includes initial removal of ammonium, nitrite, nitrate and TNT before RDX degradation can take place. |
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Keywords: | Cytochrome P-450 expression RDX degradation Rhodococcus TNT degradation TNT toxicity |
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