Viral infection of the symbiotic chlorella-like alga present in Hydra viridis.

Attempts to culture the Chlorella-like green alga found in a symbiotic association with the Florida strain of a green hydra, Hydra viridis, have been unsuccessful. Ultrastructural studies of the algae isolated from the host revealed that large (185 nm in diameter) viral particles appeared in the nuclear region of the algae 2 to 6 hr after their isolation from the hydra. By 12-20 hr, the entire population of algae was lysed. The source of the virus is unknown since it has not been detected in thin sections of intact hydra or in algal cells immediately after their isolation. The virus attached to the algal cell wall in a manner reminiscent of many bacteriophage infections. Attempts to infect three other culture-grown Chlorella strains with crude lysates or purified viral particles have been unsuccessful.