title: Involvement of cytochrome c CymA in the anaerobic metabolism of RDX by  Shewanella oneidensis  MR-1.
abstract: Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a cyclic nitramine explosive commonly used for military applications that is responsible for severe soil and groundwater contamination. In this study,  Shewanella oneidensis  MR-1 was shown to efficiently degrade RDX anaerobically (3.5 µmol·h(-1)·(g protein)(-1)) via two initial routes: (1) sequential N-NO(2) reductions to the corresponding nitroso (N-NO) derivatives (94% of initial RDX degradation) and (2) denitration followed by ring cleavage. To identify genes involved in the anaerobic metabolism of RDX, a library of ~2500 mutants of MR-1 was constructed by random transposon mutagenesis and screened for mutants with a reduced ability to degrade RDX compared with the wild type. An RDX-defective mutant (C9) was isolated that had the transposon inserted in the c-type cytochrome gene cymA. C9 transformed RDX at ~10% of the wild-type rate, with degradation occurring mostly via early ring cleavage caused by initial denitration leading to the formation of methylenedinitramine, 4-nitro-2,4-diazabutanal, formaldehyde, nitrous oxide, and ammonia. Genetic complementation of mutant C9 restored the wild-type phenotype, providing evidence that electron transport components have a role in the anaerobic reduction of RDX by MR-1.
authors.affiliation: Biotechnology Research Institute, National Research Council Canada, 6100 Royalmount Avenue, Montréal, QC, Canada.
authors.forename: Nancy N
authors.initials: NN
authors.lastname: Perreault
authors.forename: Fiona H
authors.initials: FH
authors.lastname: Crocker
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Indest
authors.forename: Jalal
authors.initials: J
authors.lastname: Hawari
mesh_terms: D000588:Amines / Q000378:metabolism; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D001711:Biotransformation; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport; D004785:Environmental Pollutants / Q000378:metabolism*; D009574:Nitro Compounds / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism; D020592:Shewanella / Q000235:genetics / Q000378:metabolism*; D014227:Triazines / Q000378:metabolism*
chemical_list: D000588:Amines; D004785:Environmental Pollutants; D009574:Nitro Compounds; D014227:Triazines; C508216:methylenedinitramine; D045304:Cytochromes c; D009609:Nitrous Oxide; C009160:cyclonite