Particle-based axenic media for tetrahymenids

Autoclavable, natural particulate media simplify axenic cultivation of tetrahymenid ciliates and presumably favor selection for phagotrophy. Viability is at least 2 months at room temperature (24-26 C) for the lipid-sensitive tetrahymenids Tetrahymena setosa, T. corlissi, T. paravorax, T. limacis, and T. patula, also for T. rostrata and (at 12 C), for strains of the T. pyriformis complex and Glaucoma chattoni. A typical medium consists of crude soy "lecithin" + skim milk powder + Saccharomyces cerevisiae cells. Other useful particules readily available commercially are: whole liver powder, cells of Micrococcus lysodeikticus and Escherichia coli, and powdered residue of liver which had been extracted with 70% ethanol ("liver No. 2). Preliminary experiments indicate that some of these media are suitable for the maintenance of Paramecium octaurelia stock 299S and Colpidium campylum. Such mixtures may serve as points of departure for devising media for more fastidious phagotrophs.