Griffith found that this combination of Streptococcus pneumoniae strains was highly severe. Live R strain + Heat-killed S strain

Live T strain + Live S strain

Heat-killed R strain + Live S strain

Heat-killed R strain + Live R strain

Live R strain + Heat-killed S strain

Explanation:

The R strain, in its live version, was nonvirulent. The ordinarily virulent S strain, when killed by heat and injected into the mice, became nonvirulent. However, when the mice were injected with both the nonvirulent R strain and the heat-killed S strain, the mice died.

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essentially, one bacterial cell splits into two daugurer cells. bacterial offspring don't need or get care from their parents because they are in a sense their own parents. that said, some bacteria can and do depend on other bacteria especially in harsh environments such as bacterial microfilms in hot water tanks.