This course aims at an audience with basic experience in microbiology. It will serve students intending to major in all disciplines in biology as opportunity to refresh existing knowledge as well as to broaden their horizon. The class starts with an overview over microbial cell structure and functions, metabolism and growth control as well as basic microbial genomics and genetics and their relevance for biotechnology. Microbial systematics and metabolic diversity will be introduced and illustrated by selected examples from different microbial taxa. Finally, the pivotal role of microorganisms in large scale ecological processes will be discussed and their interaction with other organisms, including humans, will be covered.