Gram structure of cocci

The fact that changes similar to those which exposure to acri-violet produces in B. a,nthracis and allied organisms, could not be brought about when cocci and other Gram-positive organisms were thus treated, led to the assumption in previous reports on this subject (Churchman, 1927a and 1927b) that the Gram-positivity of the two types of organism depended on a different mechanism. It has since been found, however, that the kind of changes reported for B. anthracis can be produced by other means in certain species of cocci; and that these organisms, too, probably possess a Gram-positive cortex and a Gram-negative medulla. Studies with the yeasts have been less satisfactory than those with the cocci and the results have not been sufficiently constant to warrant positive conclusions. A good deal of evidence has been accumulated, however, for the belief that the Gram structure of the yeasts is siImilar to that of B. anthracis and the cocci. It should be recalled, in this connection, that Breinl (1923) has shown that certain strains of staphylococci were changed, by what he regarded as artificial mutations, into Gram-negative forms; and that he reached the conclusion-from serological studies-that the Gram-negative forms arose from the parent strains by loss of the ectoplasm. REVERSAL OF REACTION OF THE COCCI If aqueous suspensions of certain species of cocci be exposed for ten hours or more to 52°C. their Gram reaction is completel