It is interesting to look at how this story is covered in various media out there. In the spirit of the sensationalist style of attention seeking by NASA's press office, a lot of slightly misleading stuff is being bandied about.
It is not actually "re-writing textbooks"... in spite of what the rather over-excitable Michio Kaku said. It is not even an example of natural evolution, in as much as these bacteria are not found in the wild, but are a product of a lab experiment. They are not even arsenic-based as many articles suggested. They have evolved to eat arsenic and use it in place of phosphorus and are able to incorporate it into their DNA-building processes. (Although as the Loom
article I linked to above points out, this needs to be reproduced still, it's not 100% proven).
See what Richard Dawkins says here
and PZ Myers says here
It kind of bugs me that a genuinely important science institution like NASA uses hype to promote interest in a project that while it is very interesting is not really quite what it is being made out to be. Maybe the hype will be good in that it gets the message to the public that life can exist in extreme conditions and doesn't have to necessarily have to be like us chemically. But this particular experiment has not really shown anything dramatically new, at least not new in the way the hype would lead you to believe. There is already a large body of literature on extremophiles
and this life-form is based on carbon like the rest of us. Arsenic or silicon based life might very well be possible, but this isn't "news" either.
Maybe this sort of media-circus style release does no harm, but I fear that it might turn some people off as over and over again this great so-called earth-shattering discoveries turn out to be over-hyped oversell of an interesting but not that dramatic piece of research (remember Ida
from last year)?