TRANSFORMATION OF NITROAROMATIC COMPOUNDS BY A METHANOGENIC BACTERIUM, METHANOCOCCUS SP (STRAIN-B)

The transformation of several nitroaromatic compounds by a newly isola ted methanogenic bacterium, Methanococcus sp. (strain B) was studied. The presence of nitroaromatic compounds (0.5 mM) viz., nitrobenzene, 2 ,4-dinitrobenzene, 2,4,6-trinitrobenzene, 2,4-dinitrophenol, 2,4-dinit rotoluene, and 2,6-dinitrotoluene in the culture medium did not inhibi t growth of the isolate. The bacteria grew rapidly and reached station ary phase within seven days of incubation. All the nitroaromatic compo unds tested were 80 to 100% transformed by the bacterium to amino comp ounds by a reduction process. The isolate did not use the nitroaromati c compounds as the sole source of carbon or nitrogen. The transformati on of nitroaromatic compounds by this isolate was compared to that of other methanogenic bacteria, Out of five methanogens studied, only Met hanococcus deltae and Methanococcus thermolithotrophicus could transfo rm the nitroaromatic compounds; however, the transformation rates were significantly less than that of the new isolate Methanococcus sp. (st rain B). The nitroaromatic compounds were not transformed by Methanosa rcina barkeri, Methanobacterium thermoautotrophicum, and Methanobrevib acter ruminantium.