Degradation of substituted thiophenes by bacteria isolated from activated sludge

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Abstract
Actinomycetes were isolated from activated sludge acclimated to thiophene-2-carboxylic acid (T2C) or 5-methyl-thiophene-2-carboxylic acid (T5M2C). These isolates were apparently identical and were identified as strains ofRhodococcus. The strains could grow on T2C, T5M2C, or thiophene-2-acetic acid as sole sources of carbon and energy, but could not use thiophene, methyl thiophenes, several other substituted thiophenes, dibenzothiophene, dimethyl sulfide, or pyrrole-2-carboxylic acid. T2C was degraded quantitatively to sulfate, and its carbon was converted almost entirely to cell biomass and carbon dioxide. Growth yields indicated about 25% conversion of T2C-carbon to cell-carbon. Growth was not supported by thiosulfate or methionine, nor were these compounds oxidized.Rhodococcus strain TTD-1 grown on T2C oxidized both T2C and T5M2C with an apparent Km of 1.3×10−5 M. Sulfide was also oxidized by T2C-grown organisms. This is the first demonstration of an actinomycete capable of the complete degradation of thiophene derivatives and of their use by it as sole substrates for growth.