Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Nitroreductase II Involved in 2,4,6-Trinitrotoluene Degradation: Purification and Characterization from Klebsiella sp. C1: Jung-Hye Shin , Hong-Gyu Song; J. Microbiol. 2009;47(5):536-541. Published online October 24, 2009; DOI: https://doi.org/10.1007/s12275-008-0171-6

Abstract: Three 2,4,6-trinitrotoluene (TNT) nitroreductases from Klebsiella sp. C1 have different reduction capabilities that can degrade TNT by simultaneous utilization of two initial reduction pathways. Of these, nitroreductase II was purified to homogeneity by sequential chromatographies. Nitroreductase II is an oxygen- insensitive enzyme and reduces both TNT and nitroblue tetrazolium. The N-terminal amino acid sequence of the enzyme did not show any sequence similarity with those of other nitroreductases reported. However, it transformed TNT by the reduction of nitro groups like nitroreductase I. It had a higher substrate affinity and specific activity for TNT reduction than other nitroreductases, and it showed a higher oxidation rate of NADPH with the ortho-substituted isomers of TNT metabolites (2-hydroxylaminodinitrotoluene and 2-aminodinitrotoluene) than with para-substituted compounds (4-hydroxylaminodinitrotoluene and 4-aminodinitrotoluene).

Note] Comparative Analysis of 2,4,6-Trinitrotoluene (TNT)-Induced Cellular Responses and Proteomes in Pseudomonas sp. HK-6 in Two Types of Media: Yun-Seok Cho , Bheong-Uk Lee , Hyung-Yeel Kahng , Kye-Heon Oh; J. Microbiol. 2009;47(2):220-224. Published online May 2, 2009; DOI: https://doi.org/10.1007/s12275-008-0108-0

Abstract: TNT-induced cellular responses and proteomes in Pseudomonas sp. HK-6 were comparatively analyzed in two different media: basal salts (BS) and Luria broth (LB). HK-6 cells could not degrade more than 0.5 mM TNT with BS medium, while in LB medium, they exhibited the enhanced capability to degrade as much as 3.0 mM TNT. Analysis of total cellular fatty acids in HK-6 cells suggested that the relative abundance of several saturated or unsaturated fatty acids is altered under TNT-mediated stress conditions. Scanning electron microscopy showed the presence of perforations, irregular rod formations, and wrinkled extracellular surfaces in cells under TNT stress. Proteomic analysis of soluble protein fractions from HK-6 <br>cultures grown with TNT as a substrate revealed 11 protein spots induced by TNT. Among these, seven proteins (including Alg8, AlgB, NirB, and the AhpC/Tsa family) were detected only in LB medium containing TNT. The proteins AspS, Tsf, and assimilatory nitrate reductase were increasingly expressed only in BS medium containing TNT. The protein dGTPase was found to be induced and expressed when cells were grown in either type of TNT-containing media. These results provide a better understanding of the cytotoxicity and survival mechanism used by Pseudomonas sp. HK-6 when placed under TNT stress conditions.

Simultaneous Utilization of Two Different Pathways in Degradation of 2,4,6-Trinitrotoluene by White Rot Fungus Irpex lacteus: Hyoun-Young Kim , Hong-Gyu Song; J. Microbiol. 2000;38(4):250-254.

Abstract: This study confirmed that white rot fungus Irpex lacteus was able to metabolize 2,4,6-trinitrotoluene (TNT) with two different initial transformations. In one metabolic pathway of TNT a nitro group was removed from the aromatic ring of TNT. Hydride-Meisenheimer complexes of TNT (H^- -TNT), colored dark red, were confirmed as the intermediate in this transformation by comparison with the synthetic compounds. 2,4-Dinitrotoluene as a following metabolic product was detected, and nitrite produced by denitration of H^- -TNT supported this transformation. In the other TNT pathway, nitro groups in TNT were successively reduced to amine groups via hydroxylamines. Hydroxylamino-dinitrotoluenes and amino-dinitrotoluenes were identified as the intermediates. The activity of a membrane-associated aromatic nitroreductase was detected in the cell-free extract of I. lacteus. This enzyme catalyzed the nitro group reduction of TNT with NADPH as a cofactor. Enzyme activity was not observed in the presence of molecular oxygen.

Transformations of 2,4,6-Trinitrotoluene in Various Conditions by Klebsiella sp. Strain C1 Isolated from Activated Sludge: Chong-Suk Chang , Hyoun-Young Kim , Yang-Mi Kang , Kyung Sook Bae , Hong-Gyu Song; J. Microbiol. 2002;40(3):193-198.

Abstract: Several 2,4,6-Trinitrotoluene (TNT) degrading bacteria were isolated from an activated sludge by an enrichment culture technique, and their TNT removal activities were examined. Among the isolates, strain C1 showed the highest degrading capability, and completely removed 100 or 200 mg l^-1 of TNT within 6 hours of incubation. This bacterium was identified as Klebsiella sp. The effects of different carbon sources on the removal of the parent TNT by Klebsiella sp. C1 were negligible, but the transformation rates of TNT metabolites such as amino-dinitrotoluenes and diamino-nitrotoluenes were higher with fructose addition compared to glucose addition. When nitrate was used as the nitrogen source, the degradation rates of TNT and hydroxylamino-dinitrotoluenes were higher than those with the ammonium addition. Although the TNT removal rate of Klebsiella sp. C1 was slightly higher in anaerobic conditions, the further transformations of TNT metabolites were more favorable in aerobic conditions.

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