Research ArticleMicrobiome

Effects of a gut pathobiont in a gnotobiotic mouse model of childhood undernutrition

Science Translational Medicine  23 Nov 2016:
Vol. 8, Issue 366, pp. 366ra164
DOI: 10.1126/scitranslmed.aah4669

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Neighbors matter

A big unanswered question is what determines the effects of enteropathogen burden in children who are undernourished or at risk for undernutrition. In a new study, Wagner and colleagues introduce collections of sequenced gut bacterial strains cultured from healthy or underweight Bangladeshi children into germfree mice fed diets resembling those consumed by the children. The gut bacterial strains were transplanted with or without nontoxigenic or enterotoxigenic Bacteroides fragilis strains. Addition of enterotoxigenic B. fragilis induced cachexia in the transplanted mice, and altered gene expression and metabolic activity of the transplanted bacterial strains. These effects were mitigated by cocolonization with nontoxigenic B. fragilis, illustrating the influence of intra- and interspecies interactions in determining the impact of an enteropathogen on its host.

Abstract

To model how interactions among enteropathogens and gut microbial community members contribute to undernutrition, we colonized gnotobiotic mice fed representative Bangladeshi diets with sequenced bacterial strains cultured from the fecal microbiota of two 24-month-old Bangladeshi children: one healthy and the other underweight. The undernourished donor’s bacterial collection contained an enterotoxigenic Bacteroides fragilis strain (ETBF), whereas the healthy donor’s bacterial collection contained two nontoxigenic strains of B. fragilis (NTBF). Analyses of mice harboring either the unmanipulated culture collections or systematically manipulated versions revealed that ETBF was causally related to weight loss in the context of its native community but not when introduced into the healthy donor’s community. This phenotype was transmissible from the dams to their offspring and was associated with derangements in host energy metabolism manifested by impaired tricarboxylic acid cycle activity and decreased acyl–coenzyme A utilization. NTBF reduced ETBF’s expression of its enterotoxin and mitigated the effects of ETBF on the transcriptomes of other healthy donor community members. These results illustrate how intraspecific (ETBF-NTBF) and interspecific interactions influence the effects of harboring B. fragilis.

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