[allmendream]

The RATE of mutation is changed by upregulation of error prone DNA polymerase. Where the change happens on the DNA strand is random, but the chance of it happening increases.

Another way the RATE of mutation is changed is by downregulation of DNA repair genes. These genes make proteins that patrol DNA for mismatches and repair them by assuming the old methylated strand is the good copy and the new unmethylated (until DNA methylases get to it) strand is the one that is messed up. By downregulating the DNA that codes for these repair proteins, the mutation rate goes up.

Once again, the mutations can and do happen at any position at a predictable random fashion, because DNA polymerase as a molecular machine is only 99.99% accurate, and error prone DNA polymerase is purposefully less accurate.

So why would a bacteria intentionally increase its mutation rate in response to pressure?

[metmom]

So why would a bacteria intentionally increase its mutation rate in response to pressure?

You tell me.

Good explanation of what happens, but it doesn't explain the why.