Chemotaxis and biodegradation of 3-methyl-4-nitrophenol by Ralstonia sp SJ98

3-Methyl-4-nitrophenol is one of the major breakdown products of fenitrothi on [O,O-dimethyl O-(3-methyl-4-nitrophenyl) thiophosphate], a recalcitrant organophosphate insecticide used in agriculture. Being the non-polar methyl ated aromatic compound, 3-methyl-4-nitrophenol is highly toxic and, therefo re, a complete degradation of this compound is important for environmental decontamination/bioremediation purposes. A gram negative, motile Ralstonia sp. SJ98 was isolated by selective screening from a soil sample contaminate d with pesticides. The microorganism was capable of utilizing 3-methyl-4-ni trophenol as the sole source of carbon and energy. Thin layer chromatograph y (TLC), gas chromatography (GC), gas chromatography-mass spectrometry (GC- MS), and high performance liquid chromatography (HPLC) were performed to de termine the possible intermediates in the degradative pathway of this compo und. Taken together, catechol was found to be one of the major intermediate of the pathway. Furthermore, the chemotactic behavior of Ralstonia sp. SJ9 8 towards 3-methyl-4-nitrophenol was tested using three different methods i .e., drop assay, swarm plate assay and capillary assay, which were found to be positive towards this compound. This is the first report clearly indica ting the involvement of a microorganism in the chemotaxis and biodegradatio n of methyl-4-nitro-phenol and formation of catechol as an intermediate in the degradative pathway. (C) 2000 Academic Press.