title: Ability of Acidaminococcus fermentans to oxidize trans-aconitate and decrease the accumulation of tricarballylate, a toxic end product of ruminal fermentation.
abstract: Mixed ruminal bacteria convert trans-aconitate to tricarballylate, a tricarboxylic acid which chelates blood divalent cations and decreases their availability (J. B. Russell and P. J. Van Soest, Appl. Environ. Microbiol. 47:155-159, 1984). Decreases in blood magnesium in turn cause a potentially fatal disease known as grass tetany. trans-Aconitate was stoichiometrically reduced to tricarballylate by Selenomonas ruminantium, a common ruminal bacterium in grass-fed ruminants (J. B. Russell, Appl. Environ. Microbiol. 49:120-126, 1985). When mixed ruminal bacteria were enriched with trans-aconitate, a trans-aconitate-oxidizing bacterium was also isolated (G. M. Cook, F. A. Rainey, G. Chen, E. Stackebrandt, and J. B. Russell, Int. J. Syst. Bacteriol. 44:576-578, 1994). The trans-aconitate-oxidizing bacterium was identified as Acidaminococcus fermentans, and it converted trans-aconitate to acetate, a nontoxic end product of ruminal fermentation. When S. ruminantium and A. fermentans were cocultured with trans-aconitate and glucose, tricarballylate never accumulated and all the trans-aconitate was converted to acetate. Continuous-culture studies (dilution rate, 0.1 h-1) likewise indicated that A. fermentans could outcompete S. ruminantium for trans-aconitate. When mixed ruminal bacteria were incubated in vitro with 10 mM trans-aconitate for 24 h, 45% of the trans-aconitate was converted to tricarballylate. Tricarballylate production decreased 50% if even small amounts of A. fermentans were added to the incubation mixes (0.01 mg of protein per mg of mixed bacterial protein). When A. fermentans (2 g of bacterial protein) was added directly to the rumen, the subsequent conversion of trans-aconitate to tricarballylate decreased 50%, but this effect did not persist for more than 18 h.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Section of Microbiology, Cornell University, Ithaca, New York 14853.
authors.forename: G M
authors.initials: GM
authors.lastname: Cook
authors.forename: J E
authors.initials: JE
authors.lastname: Wells
authors.forename: J B
authors.initials: JB
authors.lastname: Russell
mesh_terms: D000156:Aconitic Acid / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000209:etiology / Q000517:prevention & control; D005260:Female; D005285:Fermentation; D006089:Gram-Negative Anaerobic Bacteria / Q000254:growth & development / Q000378:metabolism; D066298:In Vitro Techniques; D010084:Oxidation-Reduction; D006109:Poaceae; D012417:Rumen / Q000378:metabolism / Q000382:microbiology; D013746:Tetany / Q000209:etiology / Q000517:prevention & control / Q000662:veterinary; D014233:Tricarboxylic Acids / Q000378:metabolism* / Q000633:toxicity; D045854:Veillonellaceae / Q000254:growth & development / Q000378:metabolism*
chemical_list: D014233:Tricarboxylic Acids; D000156:Aconitic Acid; C028021:tricarballylic acid