Schuerger and Nicholson, together with other colleagues, also performed a companion study to their experiments. They tested 26 species of bacteria commonly found living on spacecraft, subjecting them to the same harsh conditions. They found one species, Serratia liquefaciens, which managed to both survive and grow.
Where carnobacterium is specialized to live in freezing conditions, serratia liquefaciens is a generalist survival expert. The Ray Mears of the microbial world, s. liquefaciens can survive everywhere from human skin to soil to marine environments. Evidently, even Mars may not be too challenging for it. This study is especially interesting because it shows that while a lot of research has been done into extremophiles - life forms which live in the most extreme environments Earth has to offer - non-specialist life forms should not be ignored.
The biggest difference between the conditions in this experiment and the real surface of Mars is moisture. These bacteria were grown in moisture rich media, while Mars itself is exceptionally arid. Dessication would likely kill off Earth microbes which arrived on Mars quite rapidly. Whether they could survive in any damper conditions which may exist somewhere on the surface of our neighboring planet, however, isn't certain right now. The Mars Phoenix lander did discover water in the Martian permafrost, after all.