title: Enhancement of microbial 2,4,6-trinitrotoluene transformation with increased toxicity by exogenous nutrient amendment.
abstract: In this study, the bacterial strain Citrobacter youngae strain E4 was isolated from 2,4,6-trinitrotoluene (TNT)-contaminated soil and used to assess the capacity of TNT transformation with/without exogenous nutrient amendments. C. youngae E4 poorly degraded TNT without an exogenous amino nitrogen source, whereas the addition of an amino nitrogen source considerably increased the efficacy of TNT transformation in a dose-dependent manner. The enhanced TNT transformation of C. youngae E4 was mediated by increased cell growth and up-regulation of TNT nitroreductases, including NemA, NfsA and NfsB. This result indicates that the increase in TNT transformation by C. youngae E4 via nitrogen nutrient stimulation is a cometabolism process. Consistently, TNT transformation was effectively enhanced when C. youngae E4 was subjected to a TNT-contaminated soil slurry in the presence of an exogenous amino nitrogen amendment. Thus, effective enhancement of TNT transformation via the coordinated inoculation of the nutrient-responsive C. youngae E4 and an exogenous nitrogen amendment might be applicable for the remediation of TNT-contaminated soil. Although the TNT transformation was significantly enhanced by C. youngae E4 in concert with biostimulation, the 96-h LC50 value of the TNT transformation product mixture on the aquatic invertebrate Tigriopus japonicas was higher than the LC50 value of TNT alone. Our results suggest that exogenous nutrient amendment can enhance microbial TNT transformation; however, additional detoxification processes may be needed due to the increased toxicity after reduced TNT transformation.
authors.affiliation: Department of Biotechnology, National Kaohsiung Normal University, Kaohsiung, Taiwan.
authors.forename: Shih-Hsiung
authors.initials: SH
authors.lastname: Liang
authors.affiliation: Department of Biotechnology, National Kaohsiung Normal University, Kaohsiung, Taiwan.
authors.forename: Duen-Wei
authors.initials: DW
authors.lastname: Hsu
authors.affiliation: Department of Biotechnology, National Kaohsiung Normal University, Kaohsiung, Taiwan.
authors.forename: Chia-Ying
authors.initials: CY
authors.lastname: Lin
authors.affiliation: Institute of Environmental Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan.
authors.forename: Chih-Ming
authors.initials: CM
authors.lastname: Kao
authors.affiliation: Department of Environmental Resources Management, Chia Nan University of Pharmacy & Science, Tainan, Taiwan.
authors.forename: Da-Ji
authors.initials: DJ
authors.lastname: Huang
authors.affiliation: Graduate School of Biotechnology and Bioengineering, Yuan Ze University, Chung-Li, Taiwan.
authors.forename: Chih-Ching
authors.initials: CC
authors.lastname: Chien
authors.affiliation: Department of Life Sciences, National Central University, Taoyuan, Taiwan.
authors.forename: Ssu-Ching
authors.initials: SC
authors.lastname: Chen
authors.affiliation: Biodiversity Research Center, Academia Sinica, Taipei, Taiwan.
authors.forename: Isheng Jason
authors.initials: IJ
authors.lastname: Tsai
authors.affiliation: Department of Biotechnology, National Kaohsiung Normal University, Kaohsiung, Taiwan. Electronic address: cheng@nknu.edu.tw.
authors.forename: Chien-Cheng
authors.initials: CC
authors.lastname: Chen
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D001673:Biodegradation, Environmental / Q000187:drug effects; D001711:Biotransformation / Q000187:drug effects*; D002244:Carbon / Q000494:pharmacology; D002478:Cells, Cultured; D002954:Citrobacter / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D005308:Fertilizers; D009584:Nitrogen / Q000494:pharmacology; D009601:Nitroreductases / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012989:Soil Pollutants / Q000378:metabolism*; D014303:Trinitrotoluene / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D005308:Fertilizers; D012989:Soil Pollutants; D014303:Trinitrotoluene; D002244:Carbon; D009601:Nitroreductases; D009584:Nitrogen
keywords: 2; 4; 6-trinitrotoluene (TNT); Bioremediation; Cometabolism; Nitroreductase; Toxicity; Transformation