STEPWISE INTRATYPE TRANSFORMATION OF PNEUMOCOCCUS FROM R TO S BY WAY OF A VARIANT INTERMEDIATE IN CAPSULAR...

Area of Science:

• Microbiology
• Bacterial Genetics
• Immunology

Background:

• Pneumococcus exists in rough (R) and smooth (S) forms, with S forms possessing capsules crucial for virulence.
• Type II Streptococcus pneumoniae is a significant pathogen, and understanding its capsule synthesis is key to developing effective treatments.
• Genetic transformation in bacteria allows for the transfer of genetic material, influencing phenotypic characteristics.

Purpose of the Study:

• To isolate and characterize an intermediate variant of Streptococcus pneumoniae between R and S forms.
• To investigate the synthesis and immunogenicity of capsular polysaccharide in the intermediate variant.
• To explore the transformational capacity of the intermediate variant in vitro and in vivo.

Main Methods:

• Selective isolation procedures were used to obtain the intermediate variant from a Type II S strain.
• Avirulence, colony morphology, and capsule presence were assessed in the isolated variant.
• Immunological assays were performed to characterize the synthesized polysaccharide (SSSII).
• In vitro transformation experiments using R strains and in vivo conversion studies were conducted.

Main Results:

• An intermediate variant (D39/Int53) was isolated, found to be avirulent, rough, and lacking a demonstrable capsule.
• This variant synthesized SSSII, immunologically identical to Type II pneumococcal polysaccharide, albeit in smaller quantities.
• The SSSII polysaccharide was surface-localized and highly antigenic in rabbits.
• Extracts of the intermediate variant induced in vitro transformation of an R strain, enhancing SSSII production without altering colonial morphology.
• The intermediate variant was successfully converted in vivo to a fully encapsulated Type II pneumococcus, but not to Type III.

Conclusions:

• A novel intermediate pneumococcus variant was identified, possessing key genetic elements for Type II polysaccharide synthesis despite lacking a visible capsule.
• The intermediate variant serves as a precursor for encapsulated Type II pneumococci, demonstrating the dynamic nature of bacterial capsular polysaccharide expression.
• The study provides a method for preparing transforming extracts and highlights the potential for targeted genetic manipulation in pneumococcal research.