Detection of Synergistes jonesii and genetic variants in ruminants from different geographical locations

Chris S. McSweeney, Jagadish Padmanabha, Michael J. Halliday, Ben Hubbard, Leanne Dierens, Stuart E. Denman, H. Max Shelton


Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.

Leucaena leucocephala is a nutritionally rich forage tree legume that contains a toxic non-protein amino acid, mimosine, from which other toxic compounds 3,4-dihydroxypyridone (3,4-DHP) and 2,3-DHP are formed in the rumen. The rumen bacterium Synergistes jonesii is able to degrade these DHP isomers into non-toxic end products. In this study we developed new PCR-based assays to improve the specificity and sensitivity of detection of S. jonesii in the rumen. Using these new assays in a survey of ruminants from different countries showed S. jonesii appeared to be ubiquitous rather than isolated geographically. The bacterium was present as a minor population (<106 cells/mL) in the rumen and was usually comprised of several genetic variants of the species. Although the indigenous nature of S. jonesii could imply animals are protected from toxicity, the relative abundance of the bacterium, potential variation in DHP degrading ability of genetic variants of the species, and amount of leucaena in the diet may determine the ability of the resident population in the rumen to protect the animal from toxicity.

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