Gerard Muyzer is Professor in Microbial Systems Ecology at the University of Amsterdam. He is studying the structure, function and dynamics of microbial communities, their role in biogeochemical cycles and their application in biotechnological processes. For this, he is using a systems biology approach in which he combines experimental work, the use of state-of-the-art omics techniques, and mathematical modelling. He is mainly focusing on the microbial sulfur cycle, and in particular on sulfur bacteria that are present in natural ecosystems (e.g. soda lakes, stratified lakes, rhizosphere of seagrasses) as well as man-made ecosystems, such as full-scale bioreactors removing toxic sulfur compounds from wastewater. Recently, he switched his research activities to host-microbe interactions in the green alga Caulerpa.