Order of authorship in the original publication: Sonnenberg, Xu, Leip....The authors showed that complex plant carbohydrates (glycans), which the human body cannot digest, provide food for benign bacteria in the microbiome, and that feeding them appropriately maintains our symbiotic relationship with these benign bacteria. This glycan material that provides food for benign bacteria in the microbiome was later called Prebiotics. 

(Thanks to Juan Weiss for this reference and its interpretation.)