You combined DNA of heatkilled cells of smooth S strain of S

You combined DNA of heat-killed cells of smooth (S) strain of Streptococcus pneumoniae with live rough (R) strain cells of Streptococcus pneumonia in a test tube and left it for a few hours. You then spread this mixture on a plate. What type of bacterial colonies would you expect to see and why?

Solution

Bacteria growth when spread on plate:

-Virulent (deadly) colonies look smooth or like tiny droplets.
-Non-deadly bacteria formed rigid, uneven edges, basically rough colonies.
- Pneumonia caused by bacteria in mice, are \"variant\" (mutant) strain that did not kill the mice.

Results:

-R strain does not cause pneumonia
-S strain cause pneumonia.
-Heat killed S strain does not cause pneumonia
-Heat killed S strain mixed with live R Strain cause pneumonia as a substance from heat killed S strain can transform the harmless R strain into deadly strain.

-The virulent (S-strain) has a smooth polysaccharide capsule which is important for infection.
-The nonvirulent (R-strain) lacks the polysaccharide capsule, therefore it\'s appearance is rough.