Two-way pantothenate/nitrogen exchange reprograms fly metabolism and reinforces microbiota growth

Gut microbiota provide nutrients to their animal hosts, but if and how hosts reciprocate with nutrients for microbes is unclear. We show that Drosophila and their gut bacteria trade a vitamin for nitrogen sources. Acetobacter pomorum supply pantothenate (vitamin B5), which nearly doubles downstream fly coenzyme A. This is accompanied by reprogrammed fly carbohydrate metabolism. Bacteria reduce host lipid storage, dependent on both bacterial pantothenate synthesis and fly pantothenate metabolism. In exchange, bacteria promote host excretion of compounds that rescue growth of nitrogen stressed bacteria, dependent on fly pantothenate metabolism and bacterial purine metabolism. Impairing fly pantothenate metabolism reduced the in vivo bacterial population ten-fold. These results indicate a quid pro quo metabolic trade in a facultative symbiosis.