The Conversion of Certain Soluble Sugars to a Glucosan by Holotrich Ciliates in the Rumen of Sheep

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Abstract
SUMMARY: When in vitro fermentations of glucose, fructose or sucrose are carried out under conditions comparable with those in the rumen by means of relatively small inocula of strained rumen contents from hay-fed sheep, the holotrichously ciliated protozoa which are present store immense numbers of microscopic granules consisting of a practically protein-free glucosan giving a purple colour with iodine. The granules can be liberated by bursting the protozoa by the action of the synthetic detergent Teepol XL under mild conditions. An exactly similar polysaccharide granule preparation can be made from protozoa present in the rumen itself if rumen contents are withdrawn 2-41 hr. after feeding. The yield of iodophilic polysaccharide so obtained may be equivalent to approximately 25 yo of the weight of water-soluble, yeast-fermentable sugars in a single feed of hay. No granule-filled protozoa are present 9 hr. after feeding. Other simple sugars such as glucuronolactone, galactose, mannose, xylose, ara- binose, sorbose, lactose, cellobiose and maltose, are not markedly converted into polysaccharide granules by rumen protozoa, during in witro fermentation. The most obvious group of micro-organisms ordinarily inhabiting the rumen of sheep are the large ciliated protozoa. Bulk for bulk, although of course not numerically, they usually exceed the bacterial population ( Mangold, 1929). Nevertheless, they appear not to be entirely essential for the adequate func- tioning of at least some rumen fermentations, since defaunated sheep have been shown to continue to thrive (van der Wath & Myburgh, 1941; Johnson, Hamilton, Robinson & Garey, 1944). The current view is therefore, not un- naturally, that the protozoa, from the point of view of fermentation reactions, are of minor importance when compared with the rumen bacteria (see Elsden & Phillipson, 1948). A very simple experiment (recorded later) having dis- proved this extreme view in one particular instance, namely glucose fermenta- tion by the rumen contents of hay-fed sheep, it became of interest to find out the action of rumen protozoa on fermentable sugars. No claim is here made that protozoa are important in all rumen fermentations. This paper is mainly con- cerned with the storage of polysaccharide granules during carbohydrate fermentation by one important group of protozoa-the holotrichously ciliated- usually present in the sheep's rumen. METHODS

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