GRAM STRUCTURE OF COCCI

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Abstract
Previous observations to the effect that exposure to certain tri-phenyl methane dyes reverses the Gram reaction of Bacillus anthracis, reduces its size and diminishes its wt. had justified the hypothesis that this organism is composed of a Gram-negative medulla and a Gram-positive cortex. Similar results could not be obtained by exposure of cocci and other Gram-positive organisms to these dyes. However, such results can be obtained by exposing certain strains of cocci to heat (52[degree]C), in which case a reversal of Gram reaction, a diminution in size and a loss of wt. are observed. The reaction is not constant for all strains. It is entirely prevented by addition of NA2CO3. This reversal of Gram reaction is not a death phenomenon. Suggestive, though not constant, results of a similar kind were obtained with yeasts. As a working hypothesis, it would appear not unlikely, from the observations made, that all bacteria may be placed in a Gram scale, at one end of which stand the constantly Gram-negative, at the other, the constantly Gram-positive organisms. The Gram-positivity of the latter group can only be upset with difficulty, if at all; it remains positive in spite of treatment which reverses the posi-tivity of other positives. At a certain place in the scale, the Gram-negative reaction disappears; beyond this point all organisms are, when examined in young cultures and by the standard method, Gram-positive. But the Gram-positivity of many of these species may be reversed; in some of them reversal is easily brought about, in others with difficulty. Some of the processes which reverse the Gram reaction of these Gram-positives, lead also to a structural change demonstrable by staining and associated with loss of size and wt. It seems likely that it is this structural change which is the basis of reversal. The absolutely convincing evidence regarding this view, which satisfactory cross-sections of bacteria would present, can not now be offered, since no successful technique has been developed for sectioning bacteria.

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