Bacteria of the intestinal microbiota are in need for cellular structures that enable the interaction with their abiotic and biotic environment. One such machinery is the type VI secretion system (T6SS), a sophisticated molecular complex for the transport of proteins across a bacterium’s inner and outer membrane. Secreted ‘T6SS effector proteins’ have been reported across bacterial species to kill competing bacterial and fungal cells, manipulate host cells, and aid in nutrient acquisition. Although T6SSs have been identified in bacteria of the human intestinal microbiota, the structure and function of multiple proteins encoded in T6SS genes is unknown. In this SPP, we combine biophysical and molecular biology technqiues to illuminate the structure and functions of T6SS genes. Our findings will lead to a better mechanistic understanding of the cellular machineries that are used by host-associated gut microbes to interact with other microbes and the host.