Amoebae receive surprising support in defense against viruses: The bacteria they are infected with prevent them from being destroyed by giant viruses. Microbiologists have investigated how a virus infection proceeds when the amoebae are simultaneously infected with chlamydia. The research team shows for the first time that intracellular bacteria known as symbionts protect their host against viruses. Amoebae are protists, i.e. single-celled microorganisms with a cell nucleus. Protists play a key role in food webs and ecosystem processes. Consequently, the results of the study suggest that the interaction between symbionts and viruses influence the flow of nutrients in ecosystems.