1887

Abstract

SUMMARY: The capsules of bacteria and of are invisible under the phase-contrast microscope. They can be made visible through addition of a number of proteins at a certain, usually very narrow, pH range lying on the acid side of the isoelectric point of the proteins. The pH range at which the reaction occurs shifts with the isoelectric point of the protein used. The optimal pH range depends, on the other hand, upon the capsular substance of the micro-organism. The non-specific capsular reaction is elicited through a salt-like combination of several proteins with the bacterial capsule, leading to precipitation at a pH value on the alkaline side of the isoelectric point of the bacterial surface and on the acid side of the isoelectric point of the proteins. The reaction is reversible; it disappears on changing the pH. The non-specific capsular reaction at an inter-isoelectric pH zone of the bacterial surface and of the proteins is not a ‘swelling’ reaction. A swelling of the capsule might occur with some bacteria as a secondary phenomenon on the alkaline side of the reaction zone. The reaction occurs in a broader zone in members of the genus where it reveals a distinct shrinkage of the capsule at the acid side of the reacting zone.

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/content/journal/micro/10.1099/00221287-10-1-97
1954-02-01
2019-12-11
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