DOUBLET CELLS IN TETRAHYMENA AS INDICATORS OF CULTURE MEDIA COMPOSITION

Stomatogenesis in ciliates is a complex and carefully orchestrated eve nt. The exo(-) mutant SB255 of Tetrahymena thermophila has defects in mucocyst formation and docking and can also have one or two mouths. Th ree common culture media (proteose peptone, Medium 357, and yeast extr act) were analyzed for total C, N, and inorganic elements and then tes ted for their effect on the number of mouths present in SB255. Culture s of SB255 grown in Medium 357 consisted of a mixed population of cell s with either two mouths (doubler) or one mouth. Cultures from the sam e original stock grown in Medium 357 (SBm) and in 1% proteose peptone (SBpp) had different percentages of doublet tells in 1-, 2-, 3-, and 4 -d-old cultures. When transferred to and grown in 1% yeast medium, bot h SBpp and SBm cultures had increased percentages of doublets over a 4 -d culture period. When grown in 0.1, 0.5, or 1% yeast medium for 2 d, both SBpp and SBm cultures had more doublets in 1% than in either 0.1 or 0.5% yeast medium. Cultures of SBm grown in Medium 357 or 1% yeast medium for 2 d had a 10-fold increase in doublet cells compared to th e inoculum. After 2 d in 1% proteose peptone, SBm cultures had percent ages of doublet cells almost equal to that of the inoculum. Immunofluo rescence and scanning electron microscopy (SEM) were used to examine c ellular morphology of the doublet cells. These findings suggest that e nriched media promote the growth of doublet cells. Furthermore, these doublets could prove to be a useful model system for the study of biol ogical roles of trace elements.