Abstract
In earlier experiments 1 it was found that Berkefeld filtrates of synthetic medium cultures of B. enteritidis were good antigens, stimulating the production of agglutinins, precipitins, complementfixing antibodies, and possibly antitoxins when injected into rabbits. When these filtrates were concentrated by evaporation in vacuo, the products obtained were better antigens than suspensions of B. enteritidis. Protein could not be demonstrated in this material obtained by evaporation, but when the salts were dialyzed away, and the contents of the dialyzing sac were also concentrated in vacuo, the non-dialyzable residue gave very faintly positive reactions for tryptophane and histidine, and a faintly positive ninhydrin reaction, Our interest was roused in the potent antigenic substances evidently present in these bacterial culture filtrates, and a study of their nature was undertaken.
Cultures of B. enteritidis in the synthetic medium previously described 1 were incubated for 7 to 10 days, and then filtered through Berkefeld N filters. The clear filtrates were then evaporated to dryness in vacuo at a temperature not exceeding 40° C. The residue, having the consistency and appearance of brown sugar, was dialyzed in a special adaptation of the apparatus devised by Hanke and Koessler 2 until it was free from demonstrable salts.
The non-dialyzable material within the parchment bag was easily separated into three crude fractions, One of these consisted of a small quantity of fine white powder which apparently contained a considerable amount of carbohydrate. This fraction has already been briefly described, 3 and further studies are being made upon it. A second fraction was a brownish water-soluble material which, although it gave none of the usual protein reactions, probably contained some protein, since it had a nitrogen content of 6 to 7 per cent. The third fraction was brownish in color, was water-insoluble, and gave a good biuret, as well as positive vanillin and Millon tests, but negative diazo and ninhydrin reactions.
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