Question: Are most bacteria healthy?

Jane Charlesworth answered on 12 Mar 2014:

For humans, probably yes. We have a lot of bacteria living on our bodies and some of them we even need to have there in order to be healthy. For example, antibiotics are great because they kill the bacteria that make us sick, but they can also kill of nice bacteria and make us sick in different ways. A lot bacteria live in soil or water and we never meet them. And still others might make animals or plants sick but be harmless for us.