Bacteriophages for Aeromonas salmonicida were isolated from water and mud samples taken from 13 of 19 trout hatcheries and ponds examined in southern Ontario. Nine of the 13 locations were known to have histories of furunculosis disease. The bacteriophages studied formed three serological groups and two distinct morphological types. Phages of serological groups I and II possessed similar morphology; those of group III resembled the coli T-even phages. All possessed complex symmetry consisting of a head and tail with a contractile tail sheath. Latent periods of the phages ranged from 35 to 95 min and average burst sizes from 21 to 193. A group I phage and a group III phage had [Formula: see text] values of 351 and 1000, respectively.

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Osmotically sensitive protoplast-like structures were produced by the action of lysozyme on streptomycete mycelium suspended in a buffered sucrose medium. A comparison was made of the surface of the mycelium and that of the "protoplasts" by virus adsorption and serological techniques. Although the "protoplasts" did not possess the phage receptor sites present on the original hyphae they did contain antigens in common with the cell walls. These data indicated that the structures did not have properties exactly comparable to those which have been described for protoplasts from Bacillus megaterium.