Obligate anaerobes which form skatole.

Although the presence of skatole in decomposing protein materials and in feces has frequently been reported, very rarely have microorganisms been shown to form skatole in pure culture. Two species of the genus Clostridium have been described as producing skatole: Clostridium skatol Fellers and Clough (J. Bacteriol., 10, 130, 1925), which had been characterized earlier by Fellers (Abstr. Bacteriol., 7, 351, 1923), and Clostridium nauseum Spray (J. Bacteriol., 55, 839, 1948). The two organisms resemble each other in several aspects although a distinctive property of C. skatol, the formation of propionic, valeric, and caproic acids, has not been described in C. nauseum. Five clostridial cultures isolated from ensiled grass and closely resembling each other were found to form skatole, one in trace amounts only. The presence of skatole could be demonstrated with the Ehrlich and dimethylaniline reagents in cultures on peptone-yeast extractglucose media and in ether extracts or steam distillates of the cultures. On paper chromatograms of ether extracts (Dalgleish, Biochem. J., 52, 3, 1952) a single violet colored spot having the same Rf as a pure sample of skatole appeared a few minutes after spraying with the Ehrlich reagent. No immediate red color appeared on spraying, indicating the absence of indole. Skatole formation was inhibited by the addition to the medium of 0.1 per cent (w/v) cysteine, partially inhibited by 0.05 per cent (w/v) sodium thioglycolate or 0.03 per cent (w/v) sodium sulfide, and was unaffected by 0.1 per cent (w/v) ascorbic acid.