[AndrewC]

Control doesn’t imply that each mutation is part of some programmed response... So now that we are deep into a discussion over how an organism controls its mutation rate; why do you suppose there might be ANY advantage to responses that INCREASE the mutation rate over the entire genome?

Control implies what then? (in light of "an organism controls its mutation rate"). The mutations I have mentioned in the cited paper are specific to ebgA in locations 92 and 599. Second part has been answered.

[allmendream]

As I said, control involves control over the mechanisms that control the mutation rate genome wide.

And yes, increasing mutation rates under stress is an advantageous response for a bacterial population because it increases the rate of evolution.