Studies on the Rumen Flagellate Neocallimastix frontalis

Abstract

The vast increase in the population density of the rumen flagellate N. frontalis (of sheep, cattle, goats) shortly after the host animal commences eating is caused by stimulation of a reproductive body on a vegetative phase of the organism to differentiate and liberate the flagellates. The stimulant is a component of the host''s diet. The vegetative stage of N. frontalis bears a strong morphological resemblance to that of certain species of aquatic phycomycete fungi, and consists of a reproductive body borne on a single, much branched rhizoid. The flagellates liberated in vivo within 15-45 min of feeding lose their motility within 1 h and become vegetative, producing a rapid decrease in population density of the flagellates. Conditions for maximum flagellate production are similar to those occurring in the rumen: pH 6.5, 39.degree. C, absence of O2, presence of CO2. Differentiation of the reproductive body is inhibited by compounds affecting membrane structure and function, but not by inhibitors of protein synthesis. The organism was cultured in vitro in an undefined medium in the absence of bacteria or other flagellates.