Question

When living R - type of bacteria were mixed with heat killed S - type, they converted or changed to 'S' type. What is this phenomenon called ?

Answer 1

The mentioned phenomenon is Griffith's transformation principle

Griffith had discovered that he could convert the R strain into the virulent S strain. After he injected mice with R strain cells and, simultaneously, with heat-killed cells of the S strain, the mice developed pneumonia and died. In their blood, Griffith found live bacteria of the deadly S type. The S strain extract somehow had "transformed" the R strain bacteria to S form. Avery and members of his lab studied transformation in fits and starts over the next 15 years. In the early 1940s, they began a concerted effort to purify the "transforming principle" and understand its chemical nature.