[castironchef]

I understand that "bad" bacteria, those that cause disease in humans, cannot thrive in the acidic environments created by many "good" bacteria, such as those that have colonized my sourdough starter.

However, why is this? Why hasn't a "bad" bacterium evolved which can live in an acidic environment? Why would pH preference determine whether a microbe was harmful to human health?

I'm truly overjoyed that it works out like this. I'm just curious as to how we got so "lucky."

Thanks again.

P.S. Your presence on this forum is truly marvelous.

[Harold McGee]

Thanks, I’m enjoying this too.

Most microbes specialize in particular environments so that they can outgrow their competitors. And animal organs and sourdoughs (or yogurts, or sausages) are very different environments, not just in their pH, but in nutrient levels, water levels, oxygen, and so on. Fortunately!

Harold