Changes in the culture medium during the growth of B. diphtheriæ / by A.F. Watson and U. Wallace.

  • Watson, A. F.
Date:
[1924?]
Catalogue details

Licence: In copyright

Credit: Changes in the culture medium during the growth of B. diphtheriæ / by A.F. Watson and U. Wallace. Source: Wellcome Collection.

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    Table I. The changes in the amount of nitrogen in the bacterial bodies during the groivth of B. diph tlieriae. Period of growth. Ph of filtrate. Amount of nitrogen in bacterial bodies. Toxicity. Lr/500 doses per c.c. 0 days. 8-0 0 19 hours. 7-0 13 *35 mgrms. 667 23 „ 7*1 15*36 „ 1000 45 „ 7*3 38’08 2857 3 days. 8-3 37-13 „ 2857 4 ,, 8-3 38-50 2857 6 >» 8*5 33-77 „ 2500 7 „ 8-6 ... 2500 While investigating the behaviour of these culture filtrates towards various precipitating agents one interesting point came to light. It was found that the medium itself and the culture filtrates of the bacillus all gave an appreciable precipitate with glacial acetic acid, and that for the same amount of acid added there appeared to be a definite grade in the amount of precipitated material increasing with the age of the culture filtrates. With the object of investigating this point further, the following experiments were carried out. 2. The relationship Between the growth of the bacillus and the nitrogen precipitable by glacial acetic acid (“ precip- itable nitrogen ”) in the culture filtrates. As a preliminary experiment 7000 c.c. of medium were distributed in seven double Winchester quart bottles, 1000 c.c. per bottle, and incubated at 36° C. The bottles were sown with B. dijphtherice, taken out after definite* time periods and 0’5 per cent, phenol added. After twenty-four hours the contents of the bottles were filtered and the filtrates tested for toxicity by the intracutaneous method, hydrogen ion concentration and “precipitable nitrogen” in solution. For the quantitative estimation of the ‘‘precipitable nitrogen” the following technique was found to give good results. Five hundred c.c. of the filtrate were treated with 5 c.c. of glacial acetic acid and the vessels placed in boiling water for ten minutes. The solution was then allowed to cool and filtered at room temperature. The precipitate was washed with 500 c.c. of glass-distilled water after which the washings contained no detectable traces of nitrogen. The total nitrogen in the precipitate was then estimated by KjeldahTs method. Table II. shows the results of this experiment. As usual with this type of medium, film formation was very heavy, the film material from one bottle after six days’ growth containing 180 mgrms. of nitrogen. It will be seen that during the growth of the bacillus there is a steady accumulation of “ precipitable nitrogen.” As soon as growth is