RESUMO
Tetrahymena has been shown to ingest and inactivate bacteriophages, such as T4, in co-incubation experiments. In this study, Tetrahymena thermophila failed to inactivate phages PhiX174 and MS2 in co-incubations, although PhiX174 were ingested by T. thermophila, as demonstrated by: (1) recovery at defecation in a pulse-chase experiment, (2) recovery from Tetrahymena by detergent lysis, and (3) transmission electron microscopy. We conclude, therefore, that the phages must be digestion-resistant. Internalized PhiX174 were further shown to be partially protected from lethal damage by ultraviolet (UV) C and UVB irradiation. Finally, ingested PhiX174 were shown to be rapidly transported through buffer in a horizontal swimming, race tube-like assay. The transport and protection of phages may confer evolutionary advantages that explain the acquisition of digestion-resistance by some phages.
Assuntos
Bacteriófagos/fisiologia , Tetrahymena thermophila/fisiologia , Animais , Bacteriófagos/efeitos da radiação , Tetrahymena thermophila/efeitos da radiação , Tetrahymena thermophila/ultraestrutura , Tetrahymena thermophila/virologia , Raios Ultravioleta , Inativação de VírusRESUMO
Abiotic factors are thought to be primarily responsible for the loss of bacteriophages from the environment, but ingestion of phages by heterotrophs may also play a role in their elimination. Tetrahymena thermophila has been shown to ingest and inactivate bacteriophage T4 in co-incubation experiments. In this study, other Tetrahymena species were co-incubated with T4 with similar results. In addition, T. thermophila was shown to inactivate phages T5 and lambda in co-incubations. Several approaches, including direct visualization by electron microscopy, demonstrated that ingestion is required for T4 inactivation. Mucocysts were shown to have no role in the ingestion of T4. When (35)S-labeled T4 were fed to T. thermophila in a pulse-chase experiment, the degradation of two putative capsid proteins, gp23(*) and hoc, was observed. In addition, a polypeptide with the apparent molecular mass of 52 kDa was synthesized. This suggests that Tetrahymena can use phages as a minor nutrient source in the absence of bacteria.