Liang Shih-Hsiung, Hsu Duen-Wei, Lin Chia-Ying, Kao Chih-Ming, Huang Da-Ji, Chien Chih-Ching, Chen Ssu-Ching, Tsai Isheng Jason, Chen Chien-Cheng
Department of Biotechnology, National Kaohsiung Normal University, Kaohsiung, Taiwan.
Institute of Environmental Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan.
Ecotoxicol Environ Saf. 2017 Apr;138:39-46. doi: 10.1016/j.ecoenv.2016.12.012. Epub 2016 Dec 22.
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.
在本研究中，从受2,4,6-三硝基甲苯（TNT）污染的土壤中分离出幼枝柠檬酸杆菌菌株E4，并用于评估在添加/不添加外源营养物的情况下TNT的转化能力。在没有外源氨基氮源的情况下，幼枝柠檬酸杆菌E4对TNT的降解能力较差，而添加氨基氮源则以剂量依赖的方式显著提高了TNT转化的效率。幼枝柠檬酸杆菌E4对TNT转化的增强是由细胞生长增加和TNT硝基还原酶（包括NemA、NfsA和NfsB）的上调介导的。这一结果表明，幼枝柠檬酸杆菌E4通过氮营养刺激增加TNT转化是一个共代谢过程。一致地，当在添加外源氨基氮的情况下，将幼枝柠檬酸杆菌E4置于受TNT污染的土壤浆液中时，TNT转化得到有效增强。因此，通过协同接种对营养有反应的幼枝柠檬酸杆菌E4和外源氮添加物来有效增强TNT转化可能适用于修复受TNT污染的土壤。尽管幼枝柠檬酸杆菌E4与生物刺激协同作用显著增强了TNT转化，但TNT转化产物混合物对水生无脊椎动物日本虎斑猛水蚤的96小时半数致死浓度（LC50）值高于单独TNT的LC50值。我们的结果表明，外源营养添加可以增强微生物对TNT的转化；然而，由于TNT转化减少后毒性增加，可能需要额外的解毒过程。
