THE STREPTOCOCCUS LACTIS HOST-VIRUS SYSTEM I

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Abstract
The morphology of the virus 122-4 active against S. lactis agrees closely. with that reported for other viruses of S. lactis. The pH of the medium is a controlling factor in lysis of the bacteria by virus. Lysis was delayed at pH 8 and did not occur at pH values below 5. Virus adsorption was highest at pH 7. The plaque count technique gave a reliable measure of virus concn. when the size of the inoculum was kept in the range 1 to 5 x 107 cells per ml. of mixture plated. A strict proportionality existed between virus concn. and plaque count for a 20-fold range of dilution. The effect of temp. on the inactivation of virus at 30, 45, 55, and 65*C was studied.