Cell strains and culture conditions
Tetrahymena thermophila strains used in this work are listed in
Table S1 with culture conditions as previously described (Gorovsky et
al., 1975). Cells were grown in SPP medium (2% proteose peptone (GIBCO,
211684), 0.1% yeast extract (BD, 212750), 0.2% dextrose (ACROS,
41095-5000) and 0.003% EDTA, ferric-sodium salt) supplemented with 100
μg ml-1 NormocinTM (InvivoGen), an
antimicrobial reagent. Cells were grown at 30°C with agitation at
100 rpm. Cell densities were measured using a spectrophotometer (Thermo
Spectronic Unicam), where OD550 = 1 corresponds
to ~ 1 × 106 cells ml-1 (David L. Spector, 1998) or a Z1 Coulter Counter
(Beckman Coulter Inc., Indianapolis, Indiana). Cultures were generally
used during the log phase of cell growth (cell density 2-4 \(\times\)105 cells ml-1). Reagents were from
Sigma-Aldrich unless otherwise noted.