Carbon metabolism of the moderately acid-tolerant acetogen Clostridium drakei isolated from peat.

A moderately acid-tolerant, malodorous bacterium, strain FP, was isolated from peat that had a pore water pH of c. 4.2. The 16S rRNA gene sequence of FP was closely related to that of acetogens Clostridium drakei, Clostridium scatologenes, and Clostridium carboxidivorans. The DNA-DNA reassociation values obtained with DNA from FP and that of these three acetogens approximated 80%, 64%, and 59%, respectively, indicating that FP was a new strain of C. drakei. FP had broad pH and temperature ranges (3.6-7.4 and 5-40 degrees C, respectively), and metabolized a wide range of substrates, including cellobiose, glucose, xylose, vanillate, ferulate, lactate, propanol, formate, H(2)-CO(2), and CO-CO(2). Acetate was the primary reduced end product, and substrate/product stoichiometries were indicative of acetogenesis at circumneutral pH. Butyrate and H(2) became significant products from glucose at low pH. FP tolerated and could consume moderate amounts of O(2). These results (1) demonstrate that peat can harbor acetogens with a broad substrate range and tolerance to transient exposure to O(2), and (2) confirm that C. drakei, the type strain of which was originally isolated from an acidic coal mine pond, occurs in moderately acidic habitats.