Summary. Six rumen-fistulated and defaunated wethers were fed twice daily a pelleted diet of barley and dehydrated lucern at a rate of 50 g dry matter/kg body weight °-!5. Two months later, the sheep were divided into three equal groups. Each group was then inoculated in the rumen with one of the following three genera of protozoa : Polyplastron multivesiculatum (P), Entodinium sp. (E), or lsotricha prostoma (I). After two months, each group was subdivided and inoculated with an additional genus to obtain two sheep for each P + E, P + I and E + I combination. After an additional two months, two sheep were inoculated with a mixture of several genera to restore them to a conventional state. At the end of each of the four two-month periods, the total digestibility of organic matter (OM), acid detergent fiber (ADF), nitrogen (N) and fermentation in the rumen were measured.The P + E genera combination could not be obtained because E disappeared when the sheep were inoculated with the P species. However, these two genera can coexist in a rumen containing at least four different genera of protozoa.OM and ADF digestibilities were improved mainly by inoculating the P genus and, to a lesser extent, the E genus, but the effect of I was negative. N digestibility tended to be higher after ciliate inoculation, compared to the defaunated state. Furthermore, the pH in inoculated sheep was generally lower, and volatile fatty acid (VFA) and ammonia levels were higher.The composition of the VFA mixture was strongly influenced by inoculation with the E genus : the propionic acid proportion increased at the expense of the acetic and butyric acid proportions. This result was confirmed by the lower CH 4/ C0 2 ratio observed in the rumen gas composition in sheep inoculated with the E genus. With P alone or with other ciliates, the butyric acid proportion increased. The rumen lactic acid concentration increased after inoculation with the I genus. In the conventional animals, fermentation patterns were similar to those observed in the P-inoculated animals but the differences increased and became significant.Of the three ciliates studied, the P genus had the greatest effect on the digestive parameters which were similar to those found in conventional sheep. This effect could be explained by the ability of the P genus to hydrolyse and ferment most carbohydrates and by its predatory action on bacteria and protozoa.Introduction.

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The cytoplasm of the ciliated protozoan Isotricha prostoma is compartmented by a continuous fibrillar system made up of a double layer of 4 nm-diameter filaments: the microfibrillar ecto-endoplasmic boundary (EEB). Isolation of this structure after treatment of the cells in a buffer of low ionic strength in the presence of the detergent Triton X-100 evidenced connections linking the two filamentous layers. One dimensional electrophoresis on SDS-polyacrylamide gel of EEB fractions revealed several major proteins with apparent molecular weights between 11 and 23 K. Of these, two neighboring bands of MW22 and 23 K were removed from gels and used as antigens to obtain rabbit antibodies. The antiserum obtained reacted specifically with injected proteins as shown by the technique of immunological detection on nitrocellulose sheets using the peroxidase reaction product. Electron microscopy localization of the antigens with anti-IgG coupled with colloidal gold showed significant labeling of the EEB within the cortex of Isotricha permeabilized with Triton X-100. We hope that the 22-23 K antiserum will prove to be a useful tool for the comparative study of other non-actin filament systems in Protozoa.