Competition for hydrogen between sulphate-reducing bacteria and methanogenic bacteria from the human large intestine.
Sulphate-reducing activity in human faecal slurries was followed by measuring sulphide production. Sulphate-reducing bacteria (SRB) were found to outcompete methanogenic bacteria (MB) for the mutual substrate hydrogen in faecal slurries from methane- and non-methane-producing individuals mixed together. When molybdate (20 mmol/l) was added to these slurries, sulphate reduction was inhibited and methanogenesis became the major route of electron disposal. Sulphide production was stimulated by the addition of 20 mmol/l sulphate in non-methanogenic but not in methanogenic slurries. In methanogenic slurries that contained the methanogen inhibitor 2-bromoethanesulphonic acid (BES), hydrogen accumulated whilst sulphide levels were unaffected, confirming the absence of SRB in methanogenic faeces. The addition of nitrate (10 mmol/l) to faecal slurries completely inhibited methanogenesis but only slightly reduced sulphate reduction. The sulphated mucopolysaccharides, chondroitin sulphate and mucin, strongly stimulated sulphide production in non-methanogenic faecal slurries only, suggesting that these substances may be a potential source of sulphate in the large gut.
Gibson
G R
GR
Medical Research Council, Dunn Clinical Nutrition Centre, Cambridge, UK.
Cummings
J H
JH
Macfarlane
G T
GT
D000476:Alkanesulfonates; D017738:Alkanesulfonic Acids; D019605:Euryarchaeota / Q000187:drug effects / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D006859:Hydrogen; D007420:Intestine, Large / Q000382:microbiology*; D008982:Molybdenum; D009566:Nitrates; D013431:Sulfates / Q000378:metabolism*; D013440:Sulfides / Q000032:analysis
D000476:Alkanesulfonates; D017738:Alkanesulfonic Acids; D006025:Glycosaminoglycans; D009566:Nitrates; D013431:Sulfates; D013440:Sulfides; C044659:molybdate; C018853:2-bromoethanesulfonic acid; D006859:Hydrogen; D008982:Molybdenum