Microbiota-produced indole metabolites disrupt mitochondrial function and inhibit Cryptosporidium parvum growth.

Cryptosporidiosis is a leading cause of life-threatening diarrhea in young children in resource-poor settings. To explore microbial influences on susceptibility, we screened 85 microbiota-associated metabolites for their effects on Cryptosporidium parvum growth in vitro. We identify eight inhibitory metabolites in three main classes: secondary bile salts/acids, a vitamin B 6 precursor, and indoles. Growth restriction of C. parvum by indoles does not depend on the host aryl hydrocarbon receptor (AhR) pathway. Instead, treatment impairs host mitochondrial function and reduces total cellular ATP, as well as directly reducing the membrane potential in the parasite mitosome, a degenerate mitochondria. Oral administration of indoles, or reconstitution of the gut microbiota with indole-producing bacteria, delays life cycle progression of the parasite in vitro and reduces the severity of C. parvum infection in mice. Collectively, these findings indicate that microbiota metabolites impair mitochondrial function and contribute to colonization resistance to Cryptosporidium infection. [Display omitted] • The microbiota provides resistance to infection by the protozoan parasite Cryptosporidium • Indole metabolites produced by adult microbiota inhibit Cryptosporidium growth in vitro • Indoles inhibit oxidative phosphorylation and decrease ATP levels in host cells • Indoles also depolarize the mitosome in the parasite, thus likely inhibiting vital functions Funkhouser-Jones et al. show that metabolites produced by the microbiota inhibit growth of Cryptosporidium. Bacterially produced indoles impair energy production by host mitochondria and disrupt the membrane potential of the mitosome, a remnant parasite mitochondrion. These findings demonstrate the basis for resistance against enteric parasite infection provided by the microbiota. [ABSTRACT FROM AUTHOR]