Re-examination of thee metabolic potentials of the acetogens Clostridium aceticum and Clostridium formicoaceticum: chemolithoautotrophic and aromatic-dependent growth

Abstract

Both Clostridium formicoaceticum and Clostridium aceticum grew chemolithoautotrophically on carbon monoxide plus CO 2 in defined medium in the absence of carbohydrates, amino acids, or other carbon and energy sources. Formate supported the growth of both organisms as well in both defined and undefined media (both of which also contained CO 2). Hydrogen was stimulatory to the growth of C. formicoaceticum upon first transfer into H 2-enriched formate medium; however, neither chemlithoautotrophic growth at the expense of H 2 plus CO 2 nor hydrogenase could be demonstrated with this acetogen. Consistent with recent findings with other acetogens, numerous aromatic compounds were utilized by C. aceticum and C. formicoaceticum: (i) aromatic methoxyl groups were O-demethylated; (ii) aromatic acrylates were reduced; and (iii) aromatic aldehydes were oxidized. These findings demonstrate th that the metabolic potentials of these two acetogens are greater than previously recognized.