ARS | Publication request: Catabolite pathway for the production of skatole and indole acetic acid by the acetogen Clostridium drakei, Clostridium scatologenes, and swine manure

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 14, 2008
Publication Date: February 1, 2008
Citation: Whitehead, T.R., Price, N.P., Drake, H.L., Cotta, M.A. 2008. Catabolic pathway for the production of skatole and indoleacetic acid by the acetogen Clostridium drakei, Clostridium scatologenes, and swine manure. Applied and Environmental Microbiology. 74(6):1950-1953.

Interpretive Summary: Odor emanating from large-scale swine production facilities has increased the tension among rural neighbors and among urban and rural residents. Storage of swine manure is associated with the production of a variety of odorous compounds, including skatole. In order to reduce production of skatole, it is important to determine how it is synthesized. We now present the first report on the mechanism for skatole production in two bacterial species and swine manure. This information will be valuable in devising strategies to deal with the problem of odor produced from stored manure.

Technical Abstract: Skatole (3-methyl-indole) is a malodorous chemical in stored swine manure and is implicated as a component of foul tasting pork. Definitive evidence for the skatole pathway is lacking. Deuterium-labeled substrates were employed to resolve this pathway in the acetogenic bacterium Clostridium drakei and Clostridium scatologenes and to determine if a similar pathway is used by microorganisms present in stored swine manure. Indole acetic acid (IAA) was synthesized from tryptophan by both bacteria, and skatole was synthesized from both IAA and tryptophan. Microorganisms in swine manure produced skatole and other oxidation products from tryptophan, but IAA yielded only skatole. A catabolic mechanism for the synthesis of skatole is proposed.