Population levels of bifidobacterial species in continuous coculture in GOS/FOS medium (both substrates at 0.2%, wt/vol). (A) Chemostat inoculated with a combination of strains G9, G15, and G22. (B) Chemostat inoculated with a combination of strains G9, G15, and ATCC 15702. Values are means and standard errors of duplicate chemostat runs.