The End of the World?

I keep seeing adverts for things which contain "good bacteria". Which is apparently better for you than "bad bacteria".  How did we get to this?

Meeting at Bacteria HQ:

Bacteria King : "We're in trouble. They keep inventing new ways to kill us. That new Domestos could be the end. Any ideas?"
Bacteria Scientist : "But sire, I have a plan"
Bacteria King : "Do tell.."
Bacteria Scientist : "We train up some of our strongest strains for a top secret operation. We teach them the arts of subterfuge, send them undercover and get them to convince the human scum that they are friendly. Once they are safely established in their yoghurts and health drinks..."
Bacteria King : "..we strike them down. "
(all join in evil laughter)

Remember, you read it here first.