Here's a breakdown:

* R bacteria: These are non-virulent bacteria that lack the gene for a capsule, making them harmless.

* S bacteria: These are virulent bacteria that have the gene for a capsule, allowing them to evade the host's immune system and cause disease.

* Transformation: In this process, R bacteria are exposed to heat-killed S bacteria. Some of the S bacteria's genetic material, specifically the gene for the capsule, is taken up by the R bacteria. This genetic material integrates into the R bacteria's own DNA, transforming them into S bacteria.

The experiment demonstrating transformation:

This was famously demonstrated by Frederick Griffith in 1928. He injected mice with different combinations of bacteria:

* R bacteria only: Mice lived.

* S bacteria only: Mice died.

* Heat-killed S bacteria: Mice lived.

* Heat-killed S bacteria + R bacteria: Mice died.

Griffith's experiment concluded that a transforming principle from the heat-killed S bacteria was responsible for changing the harmless R bacteria into virulent S bacteria. Later research identified this transforming principle as DNA.