Our current understanding of the evolution of mutualisms is limited partly because there have been relatively few model systems for studying it in real time. A model mutualistic interaction between the bacterium D. vulgaris and the archaeaon M. maripaludis was developed to allow for rigorous tests of general hypotheses about the evolution and ecology of mutualisms. This model system also allows us to develop an evolutionary genetics perspective on an interaction that plays a key ecological role in many oxygen-free microbial communities. Here, we describe the techniques used to make anoxic media for propagating these species alone or in conditions that require their cooperation.