STUDIES IN BACTEBJOSIS. XVI:THE AGGLUTINATING AND PLASMOLYTIC ACTION OF THE SAP OF THE POTATO ON VARIOUS PARASITIC AND SAPROPHYTIC SPECIES OP BACTERIA

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Abstract
Summary.: The fresh juice of potato is shown to possess agglutinating action on certain bacteria, and strong plasmolytic power which is gradually lost on exposure to the air. The agglutinating power is found to be due to substances which are precipitated from the potato juice by 95 per cent, alcohol, and is independent of any previous inoculation of the potato with bacteria. At the natural H‐ion concentration of the potato sap the precipitate solution agglutinates and plasmolyses non‐pathogenic species to potato in varying degrees, but the pathogenic species tested were unaffected by it. The agglutinating power of the potato precipitate for any one species varies with the H‐ion concentration of the solution; each species remains unagglutinated and unplasmolysed at one definite H‐ion concentration. This point of non‐agglutination at which the species appears to be least affected by the potato precipitate, was found to be approximately the H‐ion concentration of the sap of the potato itself, i.e. about pH. 6‐2, in the case of the two species causing soft rot in the potato. The twelve species non‐pathogenic to potato which were tested have non‐agglutination points above or below this. The precipitate has a plasmolytic as well as an agglutinating action on any species at pH. values more acid than its point of non‐agglutination; this has been shown by cultural experiments to be probably dependent on the presence of phosphates in the precipitate. The agglutinating power may possibly be due to traces of salts of di‐ and tri‐valent metals in the precipitate. The writer wishes to record her indebtedness to Prof. V. H. Blackman and to Dr S. G. Paine for the laboratory facilities accorded her, and for helpful interest and criticism in the preparation of this paper. Especially her thanks are due to Dr Paine for the two photographs illustrating agglutination.