How far can the bacteria be modified?

In an interesting publication it is described, that the bacteria can be breed slowly to survive finally in a very poisonous environment.
http://www.csmonitor.com/Science/2010/1202/How-does-an-arsenic-based-life-frm-work-exactly

Probably, some irradiation (either UV or gamma-irradiation in order to increase the mutation rate) can do it even quicklier, and the possible application of the procedure may be an attempt to breed the bacteria that can survive at another planet, like Mars. Slowly, step by step it worthwhile to try generation of bacteria in an environment closer and closer to another planet. If it is possible to do for some poisonous lake, why it is not possible  for much harsher environment. Probably, the final breed can not survive on the Earth after all, but it does not any matter, the modern rocket can send it right to another planet and let them prosper. Billions of years later they may evolve into some intelligent beings.