Utilization of Complex Pectic Polysaccharides from New Zealand Plants (Tetragonia tetragonioidesand Corynocarpus laevigatus) by Gut BacteroidesSpecies

Pectic polysaccharides from New Zealand (NZ) spinach (Tetragonia tetragonioides) and karaka berries (Corynocarpus laevigatus) were extracted and analyzed. NZ spinach polysaccharides comprised mostly homogalacturonan (64.4%) and rhamnogalacturonan I (5.8%), with side chains of arabinan (8.1%), galactan (2.2%), and type II arabinogalactan (7.1%); karaka berry polysaccharides comprised homogalacturonan (21.8%) and rhamnogalacturonan I (10.0%), with greater proportions of side chains (arabinan, 15.6%; galactan, 23.8%; and type II arabinogalactan, 19.3%). Screening of gut commensal Bacteroidesshowed that six were able to grow on the NZ spinach extract, while five were able to grow on the karaka berry extract. Analysis of the polysaccharides remaining after fermentation, by size-exclusion chromatography and constituent sugar analysis, showed that the Bacteroidesspecies that grew on these two substrates showed preferences for the different pectic polysaccharide types. Our data suggest that, to completely degrade and utilize the complex pectin structures found in plants, members of Bacteroidesand other bowel bacteria work as metabolic consortia.