That's a feverishly important question in an era of mounting resistance to life-saving drugs. Unfortunately, the answers are disturbing.
Most people probably figure that bacteria rely on mutations to gain resistance to antibiotics.
Here's new information on the number of bacteria on Earth. Mutations do come into play when drug manufacturers modify an existing antibiotic to overcome resistant bugs. In that case, the bacteria already possess a gene to defeat the antibiotic, and it mutates to regain mastery over the modified antibiotic. Here's how nasty bacteria resist nice drugs. Images and caption courtesy FDA .