Microbiota protect the kidneys Chronic kidney disease (CKD) afflicts millions of people globally. The first-line treatment for CKD is dietary intervention, so there may be a gut microbiota–associated component. Lobel et al. investigated the mechanistic links between the microbiota and protein intake, because the protein metabolites indole and indoxyl sulfate are known uremic toxins (see the Perspective by Pluznick). The authors used a mouse model of CKD precipitated by a paucity of the dietary sulfur–containing amino acids methionine and cysteine. Bacterial metabolism of sulfur-containing amino acids modulated indole production by sulfide inhibition of the enzyme tryptophanase, thus abrogating uremic toxicity by this metabolite in this model system. Science , this issue p. 1518 ; see also p. 1426