This is very interesting, however, is it answering the right question? HIV and flu vaccine are specifically called out as having unusually high mutation rates. Apparently the difference is between RNA viruses and DNA viruses - the RNA ones have no "double checking" to repair errors, so have much higher mutation rates. The rates quoted here [1] put DNA viruses as similar to humans. I don't know if these phages are RNA or DNA ones (Wikipedia says there are phages of both types and while the T4 virus they have a picture of in the article appears to be DNA-based, they probably just chose it for its striking appearance).

More importantly - is mutation rate what we want to consider? Bacteria exchange DNA with each other through horizontal gene transfer and Wikipedia quotes that as the main means of transmitting antibacterial resistance, for example [2], even across species (to the extent that bacterial species are even well-defined). I'm not sure how to make the comparison with that to viral mutation rates. This [3] source gives the following interesting, but imprecise, quote:

> This antagonistic coevolution results from the constant emergence of countermeasures by which bacteria resist phages, while phages, mutating at a more rapid rate than their prey, find means to overcome this resistance.

The paper it cites [4], definitely shows phage evolution alongside bacteria evolving counter-measures. So I think that's enough to answer the original question posed, though the question of "which is evolving faster" is harder to answer and probably isn't very well-posed.

That all said, I know nothing about this field and would be happy for some better insight.

[1] http://www.nature.com/nrmicro/journal/v11/n5/box/nrmicro3003... [2] https://en.wikipedia.org/wiki/Horizontal_gene_transfer [3] http://cid.oxfordjournals.org/content/48/8/1096.full [4] http://rspb.royalsocietypublishing.org/content/royprsb/269/1...