Mimosine

Mimosine is an alkaloid, β-3-hydroxy-4 pyridone amino acid. It is a toxic non-protein free amino acid otherwise chemically similar to tyrosine, and was first isolated from Mimosa pudica. In ruminants, mimosine is degraded to 3,4 and 2,3 dihydroxy pyridone (3,4- and 2,3-DHP). It occurs in a few other Mimosa spp. and all members of the closed allied genus Leucaena.

Although toxicosis has occurred in Australia, Papua New Guinea, Africa and Florida, it has not been recorded in any other tropical and subtropical regions. Goats in Myanmar lost hair when fed to diet containing 50 % of leucaena. Goats and cattle in Hawaii are able to degrade the 3,4-DHP ruminally. Tolerance might be related to the presence or absence of microbes tolerant to mimosine and 3,4-DHP. It is known that at least Australian goats do not share the abilities of their Hawaiian counterparts.

The initial population of bacteria inoculated was not a pure culture. From this mixed culture, pure colonies of bacteria with ability to degrade the two isomers of DHP, 3,4 and 2,3 were isolated. Initially named strain 78-1 (ATCC 49833), it is strictly anaerobic when growing, can be stored at 20 &deg;C and will tolerate temperatures up to 50 &deg;C, above which it is killed. The substrates they ferment, their cell wall composition, and rRNA sequences clearly show that these bacteria are not closely related to any other in the rumen. Thus it has been assigned to a new genus and called Synergestes jonesii (Allison et al., 1992) in honour of R. J. Jones. A similar bacterium has been isolated from sheep and cattle in Venezuela and another in India.Aung from Myanmar also found new bacteria which can degrade mimosine. Attempts to transinoculate rumen liquor from goats to sheep in India have failed to improve mimosine metabolism in the latter.