Serological Properties of Products Synthesized from Sucrose by Enzymes from Different Strains of Leuconostoc Bacteria

Previous reports 1 , 2 established the fact that sterile enzyme solutions obtained from Leuconostoc mesenteroides have the capacity to synthesize a serologically reactive polysaccharide from sucrose. These studies also showed, for one strain of leuconostoc, that the polysaccharide which was formed in the absence of cells agreed in major chemical respects and in serological properties with the dextran elaborated in cultures of the living bacteria. The purpose of the present paper is to present more complete evidence on the serological agreement between the products formed by the enzyme solutions and those formed in living culture. The new experiments were made with representatives of 2 serologically different types of leuconostoc bacteria. 3 , 4 Strains of one type are characterized by the fact that their sucrose broth culture fluids cross-react in high dilution with types 2, 12 and 20 antipneumococcus serums; whereas the culture fluids of strains of the second type react in high dilution with types 2 and 20 antipneumococcus serums, but react only in low dilution with type 12 serum.

Sterile enzyme solutions were prepared 2 from sucrose broth cultures of 6 strains of Leuconostoc mesenteroides representing the 2 described sercological types. Material synthesized from sucrose by the enzymes war obtained for serological study as follows: 1 part of each enzymes solution was added aseptically to 3 parts of a sterile solution of 5% sucrose in 0.1 M. acetate buffer (pH 5.6); the enzyme-sucrose mixtures were then incubated for 5 days at 23° C, together with appropriate controls. The sterility of all the mixtures was proved by rigorous microscopic and cultural tests.

The incubated enzyme-substrate mixtures, together with supernatant fluids obtained from sucrose broth cultures of the 6 different strains, were tested in a series of dilutions against types 2, 12 and 20 antipneumococcus rabbit serums. The serum-antigen mixtures were incubated for 1 hours at 37° C and were then observed for occurrence of precipitation. The type-specificity of the reactions was controlled by tests against types 1 and 8 pneumococcus antiserums.