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. Upfront-style teaching to classes will be combined with problem-based interactive approaches. Exemplary problems will be discussed to introduce students to essential topics that will be prerequisites for Fundamental of Microbiology B 211, Advanced Environmental Microbiology B 313 and Genomics B 204. It will also provide complementary foundation to the advanced Cell Biology courses B 213 and B 224 and Synthetic Biology and Biotechnology B 206. In addition, a central aim of the class is to help students realize how deductive processes are harnessed in biological research to gain new insight.