Oxalate- and glyoxylate-dependent growth and acetogenesis by Clostridium thermoaceticum

Abstract

The acetogenic bacterium Clostridium thermoaceticum ATCC 39073 grew at the expense of the two-carbon substrates oxalate and glyoxylate. Other two- carbon substrates (acetaldehyde, acetate, ethanol, ethylene glycol, glycolaldehyde, glycolate, and glyoxal) were not growth supportive. Growth increased linearly with increasing substrate concentrations up to 45 mM oxalate and glyoxylate, and supplemental CO2 was not required for growth. Oxalate and glyoxylate yielded 4.9 and 9.4 g, respectively, of cell biomass (dry weight) per mol of substrate utilized. Acetate was the major reduced end product recovered from oxalate and glyoxylate cultures. 14C labeling studies showed that oxalate was subject to decarboxylation, and product analysis indicated that oxalate was utilized by the following reaction: 4- OOC-COO- + 5H2O → CH3COO- + 6HCO3- + OH-. Oxalate- and glyoxylate- dependent growth produced lower acetate concentrations per unit of cell biomass synthesized than did H2-, CO-, methanol-, formate-, O-methyl-, or glucose-dependent growth. Protein profiles of oxalate-grown cells were dissimilar from protein profiles of glyoxylate-, CO-, or formate-grown cells, suggesting induction of new proteins for the utilization of oxalate. C. thermoaceticum DSM 2955 and Clostridium thermoautotrophicum JW 701/3 also grew at the expense of oxalate and glyoxylate. However, oxalate and glyoxylate did not support the growth of C. thermoaceticum OMD (a nonautotrophic strain) or six other species of acetogenic bacteria tested.