The book focuses on some important microbial functions in aquatic and terrestrial environments and their influence on "global' processes and includes state-of-the-art approaches to visualization, culture and identification, community interactions and gene transfer, and diversity studies in relation to key processes. Microbial involvement in key global biogeochemical cycles is exemplified by aquatic and terrestrial examples. All major groups of gcochcmically active microbes arc represented, including cyanobactcria, bacteria, archaea, microalgae and fungi, in a wide range of habitats, reflecting the wealth of diversity in both the natural and the microbial world. This book represents environmental microbiology in its broadest sense and will help to promote exciting collaborations between microbiologists and those in complementary physical and chemical disciplines.