Interspecies H2 transfer in cellulose degradation between fibrolytic bacteria and H2-utilizing microorganisms from the human colon

Interspecies H-2 transfer between two newly isolated fibrolytic strains (18P13 and 18P16) and H-utilizing methanogen or acetogen from the human colon was investigated during in vitro cellulose degradation. Both H-2-consurnmg microorganisms utilized efficiently H2 produced from cellulose fermentation by the fibrolytic species. H2 utilization by Methanobrevibacter smithii did not change the metabolism and the cellulolytic activity of strain 18P16 whereas it induced a metabolic shift in strain 18P13. However, this metabolic shift was not associated with enhancement of cellulose degradation. In contrast, an increase in cellulose breakdown was observed when strain 18P13 was cultivated with Ruminococcus hydrogenotrophicus. This stimulating effect could be attributed to both the autotrophic and the heterotrophic metabolism of the acetogen in the coculture. (C) 2001 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.