Survival and Growth of Tetrahymena thermophila in Media that are Conventionally Used for Piscine and Mammalian Cells

The transfer of Tetrahymena thermophila from normosmotic solutions (~20–80 mOsm/kg H₂O) to hyperosmotic solutions (> 290 mOsm/kg H₂O) was investigated. During the first 24 h of transfer from proteose peptone yeast extract (PPYE) to either 10 mM HEPES or PPYE with added NaCl to give ~300 mOsm/kg H₂O, most ciliates died in HEPES but survived in PPYE. Supplementing hyperosmotic HEPES or PPYE with fetal bovine serum (FBS) enhanced survival. When ciliates were transferred from PPYE to a basal medium for vertebrate cells, L‐15 (~320 mOsm/kg H₂O), only a few survived the first 24 h but many survived when the starting cell density at transfer was high (100,000 cells/ml) or FBS was present. These results suggest that nutrients and/or osmolytes in either PPYE or FBS helped ciliates survive the switch to hyperosmotic solutions. FBS also stimulated T. thermophila growth in normosmotic HEPES and PPYE and in hyperosmotic L‐15. In L‐15 with 10% FBS, the ciliates proliferated for several months and could undergo phagocytosis and bacterivory. These cell culture systems and results can be used to explore how some Tetrahymena species function in hyperosmotic hosts and act as opportunistic pathogens of vertebrates.     

The Biology of Vampyrophrya pelagica (Chatton & Lwoff, 1930), a Histophagous Apostome Ciliate Associated with Marine Calanoid Copepods

ABSTRACT. The histophagous apostome. l'ampyrophrya pelagica , occurs on calanoid copepods in North Carolina. Its life cycle has two pathways: one when the copepod host is injured; the other when the host is ingested by an invertebrate predator. The ciliate, immediately after encysting on a copepod. metamorphoses to a feeding stage. When its host is injured or ingested by a predator, it excysts enters the wound and ingests the host's cytoplasm. In the single-host life cycle, after feeding, the ciliate encysts within the cadaver; in the two-host life cycle, after feeding it encysts upon a substrate. Encysted cells divide into 2–32 migratory tomites. Freed tomites are motionless in the water column until the water is disturbed, at which time they spring in the direction of any vibration, which many times results from a feeding copepod. Tomites select specific hosts, since not all species of copepods are infested. We hypothesize that the single-host life cycle yields many tomites that heavily infest hosts at random, and passage through the predator (two-host life cycle) results in fewer, but more widely dispersed tomites that are released continuously. The two-host life cycle is facultative for the individual, but may be obligate for the continuation of the species.