What is a bacterium that sometimes used to turn milk into different kinds of cheese?

The bacteria commonly used to turn milk into different kinds of cheese are lactic acid bacteria (LAB).

These bacteria are not a single species but a diverse group, including genera like:

* Lactococcus: *Lactococcus lactis* is a primary player in cheese production.

* Streptococcus: *Streptococcus thermophilus* is often used in combination with *Lactococcus lactis*.

* Lactobacillus: Several species of *Lactobacillus* are used for specific cheese types and flavors.

* Propionibacterium: *Propionibacterium freudenreichii* is responsible for the characteristic flavor and holes in Swiss cheese.

The specific LAB used will depend on the type of cheese being made. Each species contributes to the unique texture, flavor, and characteristics of the final product.