OXALATE-DEPENDENT AND GLYOXYLATE-DEPENDENT GROWTH AND ACETOGENESIS BYCLOSTRIDIUM-THERMOACETICUM

The acetogenic bacterium Clostridium thermoaceticum ATCC 39073 grew at the expense of the two-carbon substrates oxalate and glyoxylate. Othe r two-carbon substrates (acetaldehyde, acetate, ethanol, ethylene glyc ol, glycolaldehyde, glycolate, and glyoxal) were not growth supportive . Growth increased linearly with increasing substrate concentrations u p to 45 mM oxalate and glyoxylate, and supplemental CO2 was not requir ed for growth. Oxalate and glyoxylate yielded 4.9 and 9.4 g, respectiv ely, of cell biomass (dry weight) per mol of substrate utilized. Aceta te was the major reduced end product recovered from oxalate and glyoxy late cultures. C-14 labeling studies showed that oxalate was subject t o decarboxylation, and product analysis indicated that oxalate was uti lized by the following reaction: 4-OOC-COO- + 5H2O --> CH3COO- + 6HCO3 - + OH-. Oxalate- and glyoxylate-dependent growth produced lower aceta te concentrations per unit of cell biomass synthesized than did H-2-, CO-, methanol-, formate-, O-methyl-, or glucose-dependent growth. Prot ein profiles of oxalate-grown cells were dissimilar from protein profi les 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 exp ense of oxalate and glyoxylate. However, oxalate and glyoxylate did no t support the growth of C. thermoaceticum OMD (a nonautotrophic strain ) or six other species of acetogenic bacteria tested.