Abstract
Ureolytic activity of rumen ciliate protozoa was examined in comparison with that of rumen bacteria. Freshly obtained rumen ciliates which were washed five times with B-9 buffer solution previously, decomposed 1.3 μmole/ml of urea to give ammonia after incubation for 6 hr in the buffer solution containing streptomycin, while rumen bacterial suspension decomposed 84.6_??_97.8 μmole/ml of urea after incubation for 2 hr. The amount of ammonia-N/bacteria-N produced from urea by the suspension of rumen bacteria was usually higher than that by the coexistent suspension consisting of rumen bacteria and ciliates. When the freshly obtained rumen ciliates were previously incubated in the buffer solution containing 100 μg/ml each of streptomycin, penicillin and chloramphenicol (starved ciliates), ureolytic activity of the ciliates decreased with the incubation time and reached zero after 24 hr of incubation. 14C-Urea remained unchanged in the medium of the starved ciliates even after incubation for 6 hr. All these results led us to the conclusion that rumen ciliate protozoa did not have ureolytic activity and that ureolytic activity of the freshly obtained ciliates might be due to contaminating bacteria.
