Ellagibacter isourolithinifaciens gen. nov., sp. nov., a new member of the family Eggerthellaceae, isolated from human gut

Abstract

Urolithins are gut microbial metabolites that exert health benefits in vivo and are generated from ellagic acid (EA) and ellagitannin-containing foods such as strawberries, pomegranates and walnuts. Gordonibacter species produce some intermediary urolithins but the micro-organisms responsible for the transformation of EA into the final and more bioactive urolithins, such as urolithin A and isourolithin A, are unknown. We report here a new bacterium, capable of metabolizing EA into isourolithin A, isolated from healthy human faeces and characterized by determining phenotypic, biochemical and molecular methods. Strain CEBAS 4A belongs to the Eggerthellaceae family and differed from other genera of this family, both phylogenetically and phenotypically. Based on 16S rRNA gene sequence similarity, the strain was related to Enterorhabdus musicola DSM 19490^T (92.9 % similarity), Enterorhabdus caecimuris DSM 21839^T (92.7 % similarity), Adlercreutzia equolifaciens DSM 19450^T (92.5 % similarity), Asaccharobacter celatus DSM 18785^T (92.5 % similarity) and Parvibacter caecicola DSM 22242^T (91.2 % similarity). This strain was strictly anaerobic and Gram-stain-positive. The whole-cell fatty acids were saturated (98.3 %), a very high percentage that differs from the nearest genera ranging from 62 to 73 %. The major respiratory lipoquinone was menaquinone-7 and the diamino acid in the peptidoglycan was meso-diaminopimelic acid. Diphosphatidylglycerol and phosphatidylglycerol comprised the main polar lipid profile in addition to several phosphoglycolipids (PGL1-2), phospholipids (PL1-4), glycolipids (GL1-6) and lipids. Based on these data, a new genus, Ellagibacter gen. nov. is proposed with one species, Ellagibacter isourolithinifaciens sp. nov. The type strain of Ellagibacter isourolithinifaciens is CEBAS 4A^T (=DSM 104140^T=CCUG 70284^T).

Keywords: ellagic acid; ellagitannin; gut microbiota; isourolithin A; polyphenol metabolism; urolithin.