Application of (13)C and (15)N stable isotope probing to characterize RDX degrading microbial communities under different electron-accepting conditions.
This study identified microorganisms capable of using the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) or its metabolites as carbon and/or nitrogen sources under different electron-accepting conditions using (13)C and (15)N stable isotope probing (SIP). Mesocosms were constructed using groundwater and aquifer solids from an RDX-contaminated aquifer. The mesocosms received succinate as a carbon source and one of four electron acceptors (nitrate, manganese(IV), iron(III), or sulfate) or no additional electron acceptor (to stimulate methanogenesis). When RDX degradation was observed, subsamples from each mesocosm were removed and amended with (13)C3- or ring-(15)N3-, nitro-(15)N3-, or fully-labeled (15)N6-RDX, followed by additional incubation and isolation of labeled nucleic acids. A total of fifteen 16S rRNA sequences, clustering in α- and γ-Proteobacteria, Clostridia, and Actinobacteria, were detected in the (13)C-DNA fractions. A total of twenty seven sequences were derived from different (15)N-DNA fractions, with the sequences clustered in α- and γ-Proteobacteria, and Clostridia. Interestingly, sequences identified as Desulfosporosinus sp. (in the Clostridia) were not only observed to incorporate the labeled (13)C or (15)N from labeled RDX, but also were detected under each of the different electron-accepting conditions. The data suggest that (13)C- and (15)N-SIP can be used to characterize microbial communities involved in RDX biodegradation, and that the dominant pathway of RDX biodegradation may differ under different electron-accepting conditions.
Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA.
Kun-Ching
KC
Cho
Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA.
Do Gyun
DG
Lee
CB&I Federal Services, Lawrenceville, NJ, USA.
Mark E
ME
Fuller
CB&I Federal Services, Lawrenceville, NJ, USA.
Paul B
PB
Hatzinger
CB&I Federal Services, Lawrenceville, NJ, USA.
Charles W
CW
Condee
Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA. Electronic address: kchu@civil.tamu.edu.
Kung-Hui
KH
Chu
D039903:Actinobacteria / Q000254:growth & development*; D001673:Biodegradation, Environmental; D002247:Carbon Isotopes / Q000032:analysis*; D003013:Clostridium / Q000254:growth & development*; D020563:Gammaproteobacteria / Q000254:growth & development*; D019015:Geologic Sediments / Q000382:microbiology; D060587:Groundwater / Q000382:microbiology; D009587:Nitrogen Isotopes / Q000032:analysis*; D014227:Triazines / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D014227:Triazines; D014874:Water Pollutants, Chemical; C009160:cyclonite
Biodegradation; Electron acceptors; Explosives; RDX; SIP