Blue cheese is awful stuff lol. The mold can be on the inside like in blue cheese or it can be the rind itself such as brie. Bacteria such as Penicillium candida make up the outside of brie and cause the inside of the cheese to have that distinctive gooey smooth texture. Many cheeses have a necessary bacteria component for biochemical processes to create lactic acid. Lot of cheeses use Penicillium sp. bacteria though. If you eat yogurt then I am sure you are well aware that it is almost entirely bacteria.