title: STEPWISE INTRATYPE TRANSFORMATION OF PNEUMOCOCCUS FROM R TO S BY WAY OF A VARIANT INTERMEDIATE IN CAPSULAR POLYSACCHARIDE PRODUCTION.
abstract: 1. A variant intermediate between the classical R and S forms has been isolated by selective procedures from a rough strain of pneumococcus originally derived from Type II S. 2. The intermediate variant D39/Int53 is avirulent for mice, forms rough colonies, and does not possess a demonstrable capsule. However, it synthesizes SSSII which is immunologically indistinguishable from that produced by fully encapsulated pneumococcus Type II, though in much smaller amount. The polysaccharide is present as a surface component and as it exists in the cell is highly antigenic for rabbits. 3. An extract of the intermediate variant causes the transformation in vitro of an R strain into a variant resembling the intermediate in SSSII production but without any apparent alteration in the colonial characteristics of the R variant. 4. The intermediate variant is convertible in vivo, into a fully encapsulated strain of pneumococcus Type II. Transformation of the intermediate to a heterologous type of pneumococcus (Type III) was unsuccessful. 5. A method is described for the preparation of transforming extracts of pneumococci utilizing the massive growth of the organisms obtained in the presence of a large concentration of glucose.
authors.affiliation: Department of Bacteriology, New York University College of Medicine, New York.
authors.forename: C M
authors.initials: CM
authors.lastname: Macleod
authors.forename: M R
authors.initials: MR
authors.lastname: Krauss
mesh_terms: D000818:Animals; D004040:Dietary Carbohydrates; D005947:Glucose; D051379:Mice; D011134:Polysaccharides; D013296:Streptococcus pneumoniae
chemical_list: D004040:Dietary Carbohydrates; D011134:Polysaccharides; D005947:Glucose