The cytokine MIF controls daily rhythms of symbiont nutrition in an animal–bacterial association

What is it about?

Circadian rhythms of host animals and their microbial partners, or their microbiome, has recently become well established, but the mechanisms underlying what drives these rhythms is currently poorly understood. This problem is because many microbiomes are incredibly complex; often they comprise hundreds of microbial species interacting with a single host animal. As is so often the case, biologists turn to simple model systems to provide insights. The simpler systems have been invaluable in revealing evolutionarily conserved mechanisms, and those things that are conserved are fundamental. In the natural binary system between the bobtail squid and its partner, a luminous vibrio bacterial species, mechanisms underlying circadian rhythms are experimentally approachable. In this article, the authors show that an immune protein, macrophage migration inhibitory factor (MIF), a protein found in all animals, is critical in driving the daily rhythms of the host-microbe partnership. MIF does so by controlling food delivery to the site of bacterial symbiont colonization.

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Why is it important?

Similar to the bobail squid host, MIF has recently been found in the epithelium that supports the microbiome, and has been found to be important for the health of the partnership. While circadian rhythms have been discovered in mammalian (including human) gut epithelia, whether MIF is involved in the control of these rhythms has not been studied. The work in the squid system provides an avenue for study of MIF involvement in daily rhythms of symbiosis across the animal kingdom.

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