Biodegradation of 2-methyl, 2-ethyl, and 2-hydroxypyridine by an Arthrobacter sp isolated from subsurface sediment

A bacterium capable of degrading 2-methylpyridine was isolated by enrichmen t techniques from subsurface sediments collected from an aquifer located at an industrial site that had been contaminated with pyridine and pyridine d erivatives. The isolate, identified as an Arthrobacter sp., was capable of utilizing 2-methylpyridine, 2-ethylpyridine, and 2-hydroxypyridine as prima ry C, N, and energy sources. The isolate was also able to utilize 2-, 3-, a nd 4-hydroxybenzoate, gentisic acid, protocatechuic acid and catechol, sugg esting that it possesses a number of enzymatic pathways for the degradation of aromatic compounds. Degradation of 2-methylpyridine, 2-ethylpyridine, a nd 2-hydroxypyridine was accompanied by growth of the isolate and release o f ammonium into the medium. Degradation of 2-methylpyridine was accompanied by overproduction of riboflavin. A soluble blue pigment was produced by th e isolate during the degradation of 2-hydroxypyridine, and may be related t o the diazadiphenoquinones reportedly produced by other Arthrobacter spp. w hen grown on 2-hydroxypyridine. When provided with 2-methylpyridine, 2-ethy lpyridine, and 2-hydroxypyridine simultaneously, 2-hydroxypyridine was rapi dly and preferentially degraded; however there was no apparent biodegradati on of either 2-methylpyridine or 2-ethylpyridine until after a seven day la g. The data suggest that there are differences between the pathway for 2-hy droxypyridine degradation and the pathway(s) for 2-methylpyridine and 2-eth ylpyridine.