Some but not All Tetrahymena Species Destroy Monolayer Cultures of Cells from a Wide Range of Tissues and Species

Abstract

The activities of Tetrahymena corlissi, Tetrahymena thermophila, and Tetrahymena canadensis were studied in coculture with cell lines of insects, fish, amphibians, and mammals. These ciliates remained viable regardless of the animal cell line partner. All three species could engulf animal cells in suspension. However, if the animal cells were monolayer cultures, the monolayers were obliterated by T. corlissi and T. thermophila. Both fibroblast and epithelial monolayers were destroyed but the destruction of human cell monolayers was done more effectively by T. thermophila. By contrast, T. canadensis was unable to destroy any monolayer. At 4 °C T. thermophila and T. corlissi did not carryout phagocytosis and did not destroy monolayers, whereas T. canadensis was able to carryout phagocytosis but still could not destroy monolayers. Therefore, monolayer destruction appeared to require phagocytosis, but by itself this was insufficient. In addition, the ciliates expressed a unique swimming behavior. Tetrahymena corlissi and T. thermophila swam vigorously and repeatedly into the monolayer, which seemed to loosen or dislodge cells, whereas T. canadensis swam above the monolayer. Therefore, differences in swimming behavior might explain why T. corlissi has been reported to be a pathogen but T. canadensis has not.

Activation of an Aquareovirus, Chum Salmon Reovirus (CSV), by the CiliatesTetrahymena thermophilaandT. canadensis

“…Syncytia appeared in CHSE‐214 cultures upon the addition of T. canadensis that previously swam in fish cell cultures undergoing deterioration due to CSV infection. Unlike other Tetrahymena species, T. canadensis by itself causes no cell damage in animal cell cultures and instead swims harmlessly in the medium over intact cell monolayers (Pinheiro and Bols ). In these cultures, T. canadensis is capable of phagocytizing plastic beads, and if present, cellular debris.…”

“…T. canadensis swam above the monolayer and did not bump into the cell layer and dislodge cells from the monolayer as other Tetrahymena spp. did (Pinheiro and Bols ). The monolayers were monitored for the formation of syncytia..…”

“…), which is the medium that is commonly used to grow fish cell lines (Pinheiro and Bols ). In this medium in tissue culture flasks, T. thermophila and several other Tetrahymena species continue to swim and to phagocytize beads (Pinheiro and Bols , ). When a flask contains a monolayer of piscine or mammalian cells, T. thermophila but not T. canadensis will destroy the animal cell monolayer and ingest cellular debris into food vacuoles (Pinheiro and Bols , ).…”

“…In this medium in tissue culture flasks, T. thermophila and several other Tetrahymena species continue to swim and to phagocytize beads (Pinheiro and Bols , ). When a flask contains a monolayer of piscine or mammalian cells, T. thermophila but not T. canadensis will destroy the animal cell monolayer and ingest cellular debris into food vacuoles (Pinheiro and Bols , ). This behaviour by T. canadensis allows the potential transfer of viruses by ciliates to be studied with this species because when they have been exposed to virus and then transferred to animal cell cultures any resulting CPE in the animal cells can be attributed to only the virus.…”