Changes in immunodiffusion patterns and in nucleic acid content of Staphylococcus aureus grown in the presence of a nucleic acid fluorochrome.

Sonea, S. (University of Montreal, Montreal, Canada), J. de Repentigny, and A. Frappier. Changes in immunodiffusion patterns and in nucleic acid content of Staphylococcus aureus grown in the presence of a nucleic acid fluorochrome. J. Bacteriol. 84:1056-1060. 1962.-When grown in the presence of acridine orange, coagulase-positive Staphylococcus aureus exhibits changes in the number and the shape of its precipitin bands; these are more pronounced with commercial horse staphylococcal antitoxin than with normal human gamma-globulin. Simultaneously, there is an increase in the content of nucleic acids, especially deoxyribonucleic acid. Consequently, when grown in the presence of this nucleic acid fluorochrome, pathogenic staphylococci become similar to nonpathogenic strains in their antigenic structure and nucleic acid content. The bacterial population becomes a mixture of red and green fluorescing cells of different sizes. After centrifugation, most of the large and red fluorescing cells are found in the top layer, which shows more changes in antigenic composition and in nucleic acid content than the bottom layer. In subcultures grown in the absence of acridine orange, the cells revert to the original composition of the pathogenic strains.