Some Factors Controlling the Attachment of the Rumen Holotrich Protozoa Isotricha intestinalis and I. prostoma to Plant Particles in vitro

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Abstract
The rumen holotrich protozoa I. intestinalis and I. prostoma showed chemotaxis to sucrose, glucose and fructose. They attached themselves, by means of an organelle on the anterior cell surface, to particulate sources of these carbohydrates provided soluble protein was present in the medium. The concentration of protein eliciting attachment varied with the species and the state of nutrition of the cell, but was between 20-150 .mu.g ml-1. Attachment occurred only if the carbohydrate concentration, at its source, exceeded the chemotaxis threshold concentration (50 .mu.M for sucrose) and if it was < 1 mM. At concentrations > 1 mM, indiscriminate attachment to gas-liquid and solid-liquid interfaces occurred, provided the protein concentration was high enough to elicit attachment. In the rumen, soluble carbohydrates diffusing from food particles may attract the protozoa which attach themselves to the particles in the presence of soluble plant protein at > 20 .mu.g ml-1; these conditions exist in the host animal soon after feeding when fed infrequently. The attachment mechanism may confer an ecological advantage on the Isotricha spp. over other rumen organisms dependent on soluble carbohydrates as energy and carbon sources.