Join us for an exciting lecture by Prof. Karl Gademann, to be delivered at the GDCh-Colloquium of OV Frankfurt am Main. Abstract: The microbiome is composed of different microorganisms such as bacteria or viruses that live on or in a complex host, such as e.g. humans or plants. Estimates suggest that bacterial cells outnumber their human host cells by as much as 10:1, leading directly to the question: Who is in control? Interactions, and ultimately control of the microbiome with their host might involve the trading and trafficking of chemicals. We will present recent studies from our group investigating small molecule chemicals that serve as signals for bacterial communication, cyclitols for chemical offense, and a recent total synthesis of peyssonnoside A which might be produced by the microbiome of red algae, complemented with other terpene syntheses.