Screening of Bacillus altitudinis D47 from TNT red water-contaminated soil for highly dinitrotoluene sulfonate efficient biodegradation

Dinitrotoluene sulfonates (DNTS) as the major toxic compounds in 2,4,6-trinitrotoluene (TNT) red water-contaminated soil threaten human health and environmental safety and are hardly degraded by common soil microorganisms. Thus, isolation and characterization of the microbes with high DNTS-degrading ability is the crucial first step for bioremediation of TNT red water-contaminated sites. Here, a novel bacterial strain, namely Bacillus altitudinis D47, with a high capacity to biodegrade DNTS was isolated and identified from the TNT red water-contaminated soil. The result showed that DNTS content was reduced to 2.05% of the original amount after 3 days inoculation with B. altitudinis D47. LC-MS/MS analysis of DNTS degradation metabolites revealed B. altitudinis D47 reduced nitro-groups on DNTS to hydroxylamino- and/or amino-groups through the activity of nitroreductase (NR). Furthermore, the genome of B. altitudinis D47 was sequenced and assembled, and six NRs were retrieved in the genome. Transcriptomic analysis showed the expression of five NRs was significantly upregulated in DNTS-treated B. altitudinis D47. The enzymatic activity assay of recombinant NR proteins validated that NR1-6 can catalyze nitro reduction of DNTS in vitro. Finally, the addition of B. altitudinis D47 remarkably alleviated the phytotoxicity of DNTS to alfalfa. Overall, our work provides insights into the characteristics and molecular mechanism of B. altitudinis D47 for biodegradation of DNTS and suggests its potential application of B. altitudinis D47 in the bioremediation of TNT red water-contaminated soil.