Distribution of β-glucosidase and β-glucuronidase activity and of β-glucuronidase gene gus in human colonic bacteria

Abstract

β-Glycosidase activities present in the human colonic microbiota act on glycosidic plant secondary compounds and xenobiotics entering the colon, with potential health implications for the human host. Information on β-glycosidases is currently limited to relatively few species of bacteria from the human colonic ecosystem. We therefore screened 40 different bacterial strains that are representative of dominant bacterial groups from human faeces for β-glucosidase and β-glucuronidase activity. More than half of the low G+C% Gram-positive firmicutes harboured β-glucosidase activity, while β-glucuronidase activity was only found in some firmicutes within clostridial clusters XIVa and IV. Most of the Bifidobacterium spp. and Bacteroides thetaiotaomicron carried β-glucosidase activity. A β-glucuronidase gene belonging to family 2 glycosyl hydrolases was detected in 10 of the 40 isolates based on degenerate PCR. These included all nine isolates that gave positive assays for β-glucuronidase activity, suggesting that the degenerate PCR could provide a useful assay for the capacity to produce β-glucuronidase in the gut community. β-Glucuronidase activity was induced by growth on d-glucuronic acid, or by addition of 4-nitrophenol-glucuronide, in Roseburia hominis A2-183, while β-glucosidase activity was induced by 4-nitrophenol-glucopyranoside. Inducibility varied between strains. © 2008 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.