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From my reading on M. tuberculosis, I know that this organism has a pretty high mutation rate due to uncorrected sloppy replication, which leads to a high rate of development of spontaneous resistance to treatment.

Are there species that can beat M. tuberculosis in this degree of mutation, due to polymerase sloppiness or other mechanism?

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Do you have a reference for the "sloppiness" under normal conditions, or are you talking about in the presence of antibiotics like Moxifloxacin? –  jonsca Jul 15 '12 at 19:22
Indeed, the above was from memory. After a second look it appears that it's mainly a sloppiness during DNA repair following UV and especially oxidative stress. (PMID 12705867 and 21516081) –  rwst Jul 16 '12 at 8:03
the other way of having a high mutation rate is to be around a lot of ionizing radiation like D radiodurans... it is true that organisms 'throttle' their mutation rate by changing up their dna repair systems. Darwin's gas pedal... Given that fewer than 0.1% of the bacteria are known that exist (0.001%? the jury is still out), its possible some amazing discoveries will turn up later too. –  shigeta Sep 20 '12 at 13:09
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You seem to be assuming that mutation rates are somehow constant over evolutionary time. They are not. Mutation rates will change according to the stresses a species is subjected to. If you take a bacterial population and place it in a stressful environment (high/low temperatures, oxidative stress, lack of nourishment or whatever) you are likely to see an increase in the mutation rate.

That said, this review and references therein might interest you:

E. Denamur and I. Matic,Evolution of mutation rates in bacteria,Molecular Microbiology 60(4), pages 820–827, May 2006

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Huh, that's news to me. In fact, Mtb has a rather low mutation rate and rather low genetic variance. See the paper by Sherman & Gagneux in Nature genetics. The paper does state that mutation rate in latent infection is higher than expected or previously assumed, but that's a different story.

That said, mutation rate depends strongly on the genomic context. You can have mutator strains in E. coli or other bacteria that exceed the mutation rates of other strains by orders of magnitude.

A clinical example of a bacterium with mutator strains that help in acquiring resistance is Pseudomonas aeruginosa. More on that in the paper by Ferroni et al..

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