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Abstract
Summary: The best labelling of Staphylococcus aureus (var. pyogenes) with 2P was achieved when the organisms were grown in broth containing 33 μg. ortho- phosphate/ml. and 150–200 μ c./ml. 2P. Cocci labelled in this way were as virulent to mice as control cocci. The phosphorus content of cocci was proportional to the orthophosphate content of the medium over the range 5 μg.-300 μg. PO4/ml. 2P was released from cocci when they were incubated with phosphate buffer and other media which did not support cell division. 2P was released from labelled dividing cocci grown in nonradioactive media. About 80% of the 2P was released during division; a maximum of about 55% was released from non-dividing cocci over a similar time period. Most of the 2P released from dividing cocci was present in the form of molecules non-diffusible in dialysis (80%); most of the 2P released into phosphate buffer was diffusible. Cocci deficient or rich in phosphorus were fractionated with trichloroacetic acid (TCA), ether, ethanol and perchloric acid. Cocci containing low amounts of P lacked 2P in the fraction soluble in cold TCA, about 80% of which was orthophosphate. Cocci deficient in phosphorus incorporated 2P from 2PO4 solutions more rapidly than enriched cocci. The distributions of 2P in cocci previously rich or deficient in P were similar, but labelling in deficient cocci was increased in the RNA-containing fraction; and that part of the fraction soluble in hot TCA which had a barium salt insoluble at pH 4. The phosphorus level in the cells had no effect on the amount of phosphorus released into phosphate buffer solution.
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