A structured account of the full range of environments in Antarctica and of the microbial communities that live within them. The author examines the major features of the chemical and physical environment in each habitat, and the influence of these features on the population structure and dynamics of their microbiota. Each chapter considers a specific type of environment, the microbial species that dominate, their community structure and dynamics, and the microbial processes that operate and have been measured in the ecosystem. The chapters conclude with an overview of the ecosystem trophic structure and an introduction to the larger organisms that depend on the microbiota. Separate chapters examine the range of cellular strategies adopted by microorganisms within the Antarctic environment, and the increasing influence of humans on these communities.