Microbial transformations can take us out of this world, literally and figuratively. In the review by Nealson and Cox (pp 296–300), we learn about a broad range of metabolism that has been discovered recently and holds great importance for bioremediation in the modern world, even though it is probably ancient in origin. The microbial reduction of metals may be some of the most fundamental electron transfer reactions of single-celled organisms, and evolved early after the inception of life on Planet Earth. In this context, Nealson points out that these may be among our best signature reactions for discerning whether biotransformations are occurring, or have occurred, on other planetary bodies in our solar system. The search for life on other planets has also provided impetus for further study of psychrophilic, or cold-loving, bacteria on earth. The review by Deming (pp 301–309) describes recent progress in understanding the physiology of bacteria that inhabit such environments as Antarctic frozen lakes. These studies also have earthly interest. Industries are finding increasing applications for enzymes that are active at cold temperatures, and psychrophiles are an obvious source of these biocatalysts. Thus, microbial ecology continues to expand its boundaries, into the inner depths of soil particles on Earth and beyond our planet in the quest for life outside Earth’s boundaries.