A remarkable disintegrative effect of skatole upon certain rumen ciliate protozoa.

Abstract

Hogg and Elliott1 noted that indole and skatole were both highly toxic towards the aerobic free-living ciliate Tetrahymena pyriformis. A concentration of 0.01 per cent of indole, for example, killed all organisms in a vigorous culture in two hours, but these workers made no mention of any characteristic change in appearance of the cells. We have now shown that these substances are highly toxic to the anaerobic ciliates of the sheep's rumen, particularly the holotrichs (Isotricha and Dasytricha) and also Ophryoscolex. These ciliates had been separated from strained rumen contents, washed and maintained alive and active for several hours in a phosphate buffer (without antibiotic) at pH 7.2 as described by Heald, Sugden and Oxford2. On a molecular basis skatole was much more toxic than indole to the rumen ciliates; but if the comparison was made at concentrations near saturation in the buffer employed, indole being the more soluble compound, the respective effects upon the final appearance of the cells were almost equally spectacular. Briefly, not only did all ciliary motion cease in two hours at 37°, but also a phenomenon resembling a drastic mechanical disintegration took place. The outer pellicles of the holotrichs, and also of Ophryoscolex, were torn asunder with liberation of the internal contents of the cells, so that after gently shaking the tube, instead of the rapid re-formation of a layer of ciliates at the bottom below a clear supernatant, there was a dense uniform turbidity throughout due to the release of storage polysaccharide granules and other inclusions from the disrupted cells.