ORGANIC-ACIDS AND STABLE-ISOTOPE METABOLIC STUDIES OF A THERMOPHILIC SULFUR-DEPENDENT ANAEROBIC ARCHAEON

Organic acids were analyzed as tert-butyldimethylsilyl derivatives by gas chromatography and gas chromatography-mass spectrometry in culture s of an extremely thermophilic sulfur-dependent anaerobic archaeon, st rain ST 546, isolated from a deep-sea hydrothermal vent. Quantitative data indicate the formation of propanoic, 2-methylpropanoic, 3-(methyl thio)propanoic, phenylacetic, 4-hydroxyphenylacetic, and indole-3-acet ic acids (all detected at the millimolar level) and one compound tenta tively identified to 2- and/or 3-methylbutanoic acid in peptone media. In addition to these compounds, formic and 2-hydroxypropanoic acids ( all the acids detected at the sub-millimolar level) along with another compound are associated with the 20 amino-acid containing medium cult ure. Use of stable-isotope labeled amino acids demonstrated that 3-(me thylthio)propanoic acid originates from L-methionine whereas L-phenyla lanine yields phenylacetic acid, but not 4-hydroxyphenylacetic acid.