title: Effect of organic and inorganic nitrogenous compounds on RDX degradation and cytochrome P-450 expression in Rhodococcus strain YH1.
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.
authors.affiliation: 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.
authors.forename: Ali
authors.initials: A
authors.lastname: Nejidat
authors.forename: Limor
authors.initials: L
authors.lastname: Kafka
authors.forename: Yoram
authors.initials: Y
authors.lastname: Tekoah
authors.forename: Zeev
authors.initials: Z
authors.lastname: Ronen
mesh_terms: D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007287:Inorganic Chemicals / Q000737:chemistry / Q000494:pharmacology*; D008797:Metyrapone / Q000494:pharmacology; D015394:Molecular Structure; D017672:Nitrogen Compounds / Q000737:chemistry / Q000494:pharmacology*; D012240:Rhodococcus / Q000187:drug effects* / Q000201:enzymology*; D014227:Triazines / Q000737:chemistry / Q000378:metabolism*
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D007287:Inorganic Chemicals; D017672:Nitrogen Compounds; D014227:Triazines; D003577:Cytochrome P-450 Enzyme System; C009160:cyclonite; D008797:Metyrapone