Abstract
If a divided gentian violet plate be stroked with a thick suspension of the Gram positive and gentian positive B. subtilis no growth whatever will ever occur on the gentian violet side of the plate. The organism will, indeed, refuse to grow up to the dividing line between plain and gentian violet agar, ceasing sharply at a point about 1/2 to 1 cm. from this line.
If, however, the gentian violet half of the plate be repeatedly re-inoculated with thick smears, a moderate growth—in some instances a fairly vigorous growth—occurs. This is not due to acquisition by the bacteria of resistance to the dye, for if the organisms, which have thus grown, be transplanted to gentian violet agar they will not grow in the presence of the dye. Nor is it due to insufficiency of dye, for in the plates used in the experiments dye was used in strengths greatly in excess (1-100,000) of the strength necessary to prevent the growth of B. subtilis (1-1,000,-000).
The explanation of the phenomenon is not at present perfectly clear, but there is some reason for believing that it may be due to a property of bacteria-not hitherto recognized-of communal action. A few studies of single stained bacterial cells, made by the method of Barbour, lend support to this explanation.
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