phi 227, a temperate phage from a group H streptococcus (Streptococcus sanguis), was propagated vegetatively in group H strain Wicky 4-EryR, and its characteristics were determined. A procedure dependent on multiplicity of
infection, incubation time, and treatment of crude lysates with
diatomaceous earth was found to optimize phage yield, resulting in titers of 1 X 10(10) to 2 X 10(10) PFU/ml. Without prior treatment with
diatomaceous earth, subsequent purification procedures (
methanol,
ammonium sulfate,
polyethylene glycol) gave recoveries of less than 1% of crude lysate titers. Adsorption of phi227 to host cells was relatively unaffected by the medium, but
calcium (not substituted by
magnesium) was required for formation of infectious centers. The
phage receptor was present on purified cell walls, resisted
trypsin and heat, and was removed ty
hydrochloric acid, trichloracetic
acid, and hot
formamide: however,
formamide-extracted material failed to inactivate phage, and the nature of the receptor is unknown. Single-step growth experiments showed a latent period of 39 min and a burst size of 100 PFU/infectious center; results were unaffected by omission of supplemental Ca2+, by supplementation with Mg2, addition of
glucose, or changes of pH between 6.35 and 8.0; but increased temperature (40 to 43 degrees C) shortened the latent period and decreased the burst size. The latent period was prolonged in genetically competent host cells and in chemically defined medium; and in the latter, the burst size was smaller. Phage replication was sensitive to those metabolic inhibitors which inhibited the host streptococcus: these included
rifampin,
fluorodeoxyuridine,
hydroxyurea,
dihydrostreptomycin, and 6-P-hydroxyphenylazouracil. The data suggest that phi227 does not code for a
rifampin-resistant
RNA polymerase. However, in a
rifampin-resistant host strain, phage replication and lysogen formation were both decreased suggesting that altered host core polymerase had less affinity for (some) promotors on the phi227 template. In transfection, a Ca2+-dependent stabilization step that was inhibited by Mg2+ was demonstrated; transformation was not affected by either Ca2+ or Mg2+, and the site and nature of the stabilization are unknown. More than one molecule of
DNA was required for plaque formation. Biophysical characterization showed a type B phage of buoyant density (
CsCl) 1.50, containing five
proteins and 54.8%
DNA. The duplex linear
DNA had a molecular weight (calculated from contour length) of 23.2 X 10(6) and a
guanine plus
cytosine content (calculated from melting point) of 42.3 mol%. Similar characterizations of streptococcal phages, including biophysical data, have not been previously available.