Fatty Acid Requirements of Certain Rumen Bacteria

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Abstract
Cultures were isolated from 108 dilutions of rumen material in roll-tubes of a trypticase-phytone-glucose basal medium supplemented with rumen fluid. Almost one-fourth of the isolates failed to grow on subculture in the basal medium unless it was enriched with rumen fluid or a mixture of fatty acids commonly found in the rumen. Five representative isolates from this group grew well with a combination of n-valerate and isovalerate replacing the rumen fluid or the fatty-acid mixture. None grew with n-valerate as the sole additive to the basal medium, but all grew appreciably with isovalerate. Four of the 5 grew considerably better with a mixture of the 2 acids than with isovalerate alone. One of the cultures was tentatively identified as a Borrelia species and 2 as Bacteroides succinogenes. The other 2 organisms were not identified as recognized species.