A new low cost microbiotest with the freshwater ciliate protozoan Spirostomum ambiguum : Definition of culturing conditions

This paper reports on preliminary experiments on the controlled culturing of the freshwater ciliated protozoan Spirostomum ambiguum, as a first step in the development of a new low cost microbiotest, to complement the limited battery of standardized cost-effective toxicity tests presently available, with a representative of unicellular biota. Three strains of S. ambiguum originating from France and Poland respectively, have been grown in natural as well as in reconstituted waters, on several types of inert diets and in different temperature and light conditions. The best results in terms of survival and reproduction of the ciliates, leading to a standard recipe for stock culturing, were obtained at 20 degree C, in reconstituted Volvic water and on a diet of oat flakes supplemented with dried leave powder as vegetal adjuvant, with weekly renewal of the medium and food. An average generation time of 4 days was obtained in the latter set of stock culturing conditions.