Biodiversity of Microbial Life places the importance and novelty of the diversity of the microbial world in perspective with the biodiversity of plants and animals. Microbial diversity has driven the evolution of all life on Earth as well as the nutrient cycles, which are key to the operation of the biosphere. Microorganisms live in all ecosystems, even extreme environments not habitable to other organisms. Noted experts including Carl Woese, the originator of the Tree of Life, and Rita Colwell, who is now Director of the National Science Foundation, offer their unique perspectives on the extent and importance of microbial biodiversity. Special emphasis is placed on: * Evolution, speciation, and contrasts between microbial biodiversity and plant and animal biodiversity * Physiological and metabolic diversity of microorganisms * Biodiversity of microbial life in terrestrial and marine environments * Symbioses between microorganisms and plants, insects, and humans * Extreme environments populated exclusively or primarily by microorganisms including thermal vents and hot springs, polar sea ice environments, and subterranean ecosystems * Microorganisms and biotechnology Biodiversity of Microbial Life is an essential resource for all biologists interested in biodiversity.