Competition for glucose between Candida albicans and oral bacteria grown in mixed culture in a chemostat

The competition for glucose as a growth-limiting substrate between Candida albicans and a mixed community of oral bacteria was investigated. A chemostat was operated under glucose-limiting and glucose excess conditions at a dilution rate of 0.05/h. A mixed population of oral bacteria was established and after a steady state had been reached the chemostat was inoculated with C. albicans. Seven bacterial species Streptococcus sanguis, S. sobrinus, S. mitis, Lactobacillus casei, Veillonella dispar, Eubacterium saburreum and Fusobacterium nucleatum - were able to establish stable populations under glucose-limiting conditions. The yeast was unable to grow with the bacteria under glucose limitation. Only three bacterial species, S, sobrinus, L, casei acid E, saburreum, became established under glucose-excess conditions. C, albicans was also able to become established in the glucose-excess chemostat and could grow and maintain a steady state in a mixed culture with these organisms. L, casei, S, mitis and S, sobrinus had faster glucose consumption rates than C. albicans. All the bacteria, except for F. nucleatum, had maximum specific growth rates higher than C. albicans, The results suggest that glucose may act as a growth-limiting substrate for C. albicans in the establishment and growth of the yeast in a mixed community of oral bacteria.