THE STREPTOCOCCUS LACTIS HOST-VIRUS SYSTEM II

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Abstract
The adsorption of virus by S. lactis 122-4 was about 3 times as great in a medium consisting of 1% tryptone, 0.3% yeast extract, and 0.2% glucose as in the same medium when tryptone was omitted. On a wt. basis, yeast extract replaced tryptone for virus adsorption. Salt stimulation of cellular lysis by virus can be used as a method of screening electrolytes for effects on virus adsorption. Electrolytes were most stimulating for both cellular lysis and virus adsorption at concns. ranging from 0.005 [image]to 0.05 [image]. Potassium phosphate, KC1, NaCl, CaCl2, MgSO4 and Na acetate promoted lysis of the host cells according to their efficiency in promoting virus adsorption, as measured by plaque count assays. Na citrate did not permit lysis of host cells by virus although it allowed maximum adsorption and did not inactivate the virus. Virus synthesis was greatly reduced in the presence of 0.005 M citrate. This level of salt is somewhat inhibitory to multiplication of the bacteria. Addition of 0.02 [image]CaCl2 did not release the citrate inhibition except to permit cellular lysis after a very long lag period. The avg. yield of virus per infected cell of S. lactis 122-4 in tryptone yeast extract medium at pH 7 and 30 C was about 70 plaque-forming particles. The burst size was reduced by a factor of 3 when tryptone was not present in the medium even though adsorption of virus was maintained at a high level by the addition of potassium phosphate to give a 0.01 [image] concn. On a wt. basis, yeast extract only partly replaced tryptone for virus synthesis. This suggests that this host-virus system requires growth factors that are not entirely supplied by yeast extract.

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