Microorganisms are key players in all the major biogeochemical cycles on Earth. Fluxes, Cycles, and Microbial Communities explores the microbial influence on the biological, chemical, and geological processes that shape natural environments on our planet. This is currently an area of intense research activity given the extent to which humans have been modifying the natural world, which have potential consequences for ecosystems, the biosphere, and Earth’s climate. Microorganisms have a critical role in these processes as major controllers of elemental fluxes, ecosystem functioning, and as producers and consumers of major greenhouse gases. This module will introduce students to the diversity of life that has been shaping our biosphere since the early beginnings of life, and that continues to shape our biosphere in the Anthropocene. Key environments such as forest and oceans are also specifically covered.