Question

Which of the following correctly describes the difference between R and S-strains of Streptococcus pneumoniae (pneumococcus) bacteria in Frederick Griffith’s experiment?

• A. Mice infected with the S-strain(virulent) do not develop pneumonia but mice infected with the R-strain(non-virulent) develop pneumonia.
• B. The S-strain bacteria produce rough colonies, while the R-strain produces smooth colonies.
• C. The S-strain bacteria have a lipid coat while R-strain bacteria have a mucous coat.
• D. The S-strain bacteria have a mucous (polysaccharide) coat while R-strain does not.

Answer 1

The correct option is D The S-strain bacteria have a mucous (polysaccharide) coat while R-strain does not.

The S-strain of Streptococcus pneumoniae (pneumococcus) bacteria in Frederick Griffith’s experiment has a mucous (polysaccharide) coat while the R-strain does not.
Therefore, S-strain bacteria produce smooth shiny colonies while the R-strain produces rough colonies. Mice infected with the S-strain (virulent) died from pneumonia infection but mice infected with the R-strain (non-virulent) did not develop pneumonia.