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Appl Microbiol. Jan 1969; 17(1): 83–87.
PMCID: PMC377617

Volatile Fatty Acids and the Inhibition of Escherichia coli Growth by Rumen Fluid1

Abstract

Concentrations of volatile fatty acids (VFA) normally found in bovine rumen fluid inhibited growth of Escherichia coli in Antibiotic Medium 3. Acetic, propionic, and butyric acids each produced growth inhibition which was markedly pH-dependent. Little inhibition was observed at pH 7.0, and inhibition increased with decreasing pH. A combination of 60 μmoles of acetate, 20 μmoles of propionate, and 15 μmoles of butyrate per ml gave 96, 69, and 2% inhibition at pH 6.0, 6.5, and 7.0, respectively. Rumen fluid (50%) gave 89 and 48% inhibition at pH 6.0 and 6.5, respectively, and growth stimulation (22%) at pH 7.0. Rumen fluid inhibitory activity was heat-stable, was not precipitated by 63% ethyl alcohol, and was lost by dialysis and by treatment with anion-exchange resins but not with cation-exchange resins. These results are consistent with the idea that VFA are the inhibitory substances in rumen fluid. Previous results which indicated that rumen fluid VFA did not inhibit E. coli growth were due to lack of careful control of the final pH of the growth medium. The E. coli strain used does not grow in rumen fluid alone at pH 7.0.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Brownlie LE, Grau FH. Effect of food intake on growth and survival of salmonellas and Escherichia coli in the bovine rumen. J Gen Microbiol. 1967 Jan;46(1):125–134. [PubMed]
  • Hollowell CA, Wolin MJ. Basis for the exclusion of Escherichia coli from the rumen ecosystem. Appl Microbiol. 1965 Nov;13(6):918–924. [PMC free article] [PubMed]
  • MEYNELL GG. Antibacterial mechanisms of the mouse gut. II. The role of Eh and volatile fatty acids in the normal gut. Br J Exp Pathol. 1963 Apr;44:209–219. [PMC free article] [PubMed]

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