Microorganisms are the dominant life forms on our planet and are found in every possible ecosystem. They represent the largest biodiversity on the planet with immense genetic and functional potential. Microbes provide essential functions to the environment or host they live with. By catalyzing essential biogeochemical processes they drive the global nutrient cycles. As symbionts, they determine the well-being of their host by providing nutrients and protection against biotic and abiotic stresses. However, these functions are typically a result of an active microbial community and not provided by a single species or by a single cell. Such a complex community is termed microbiota. The microbiome refers to the entire habitat with its microbes, the collective genomic information (i.e. metagenome), surrounding environmental conditions, their metabolic activities, and ecological functions.

Current microbiome research aims to reveal the microbiota composition, its distribution and temporal dynamics, and, most importantly, its function for the ecosystem or the host. This knowledge is essential in order to exploit or manipulate the microbiota to maintain a clean environment, ameliorate the consequences of global change, or support the health of its host.