title: Identification of hexahydro-1,3,5-trinitro-1,3,5-triazine-degrading microorganisms via 15N-stable isotope probing.
abstract: This study reported the application of 15N-stable isotope probing (SIP) to identify active hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)-utilizing microorganisms in groundwater microcosms. Fifteen 16S rRNA gene sequences were derived from the 15N-DNA fraction (contributed from active microorganisms capable of using RDX as a nitrogen source) of microcosms receiving cheese whey. The 16S rRNA gene sequences belonged to Actinobacteria (two clones), alpha-Proteobacteria (seven clones), and gamma-Proteobacteria (six clones). Except for five sequences with high similarity to two known RDX degraders (Enterobacter cloacae and Pseudomonas fluorescens I-C), our results suggested that phylogenetically diverse microorganisms were capable of using RDX as a nitrogen source. Six sequences of the xplA gene (a known RDX-degrading catabolic gene) were detected from the 15N-DNA fraction. The xplA gene sequences were 96-99% similar to the xplA gene of Rhodococcus sp. DN22(a known RDX utilizer), suggesting that other RDX utilizers might contain xplA-like genes. Twenty-five 16S rRNA gene sequences recovered from the unenriched, RDX-contaminated groundwater clustered differently from those obtained from the 15N-DNA fraction of the cheese-whey-amended microcosm. Our results suggested that active RDX utilizers can be stimulated by nutrient source additions even if they are present at low densities, and that use of 15N-SIP can identifythese functional members of the microbial community.
authors.affiliation: Zachry Department of Civil Engineering, Texas A&M University, College Station, Texas 77843-3136, USA.
authors.forename: Hyungkeun
authors.initials: H
authors.lastname: Roh
authors.forename: Chang-Ping
authors.initials: CP
authors.lastname: Yu
authors.forename: Mark E
authors.initials: ME
authors.lastname: Fuller
authors.forename: Kung-Hui
authors.initials: KH
authors.lastname: Chu
mesh_terms: D039903:Actinobacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D017931:DNA Primers; D009587:Nitrogen Isotopes; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D020560:Proteobacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013045:Species Specificity; D013056:Spectrophotometry, Ultraviolet; D014227:Triazines / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D009587:Nitrogen Isotopes; D012336:RNA, Ribosomal, 16S; D014227:Triazines; D014874:Water Pollutants, Chemical; C009160:cyclonite