1.   In vitro, sulphate reducing bacteria compete with methanogenic bacteria for hydrogen when sulphate is present.

2.   In non-methanogenic subjects, sulphate reducing bacteria consume some of the hydrogen produced in fermentation.

3.   In responders, viable counts of methanogenic bacteria decreased in the presence of extra sulphate in the diet while sulphate reducing bacteria were detected in low numbers.

4.   In previous studies we have shown that in the colon of non-methanogenic human subjects, significant populationsof sulphate reducing bacteria exist.

5.   In marine sediments and faeces, sulphate reducing bacteria outcompete methanogenic bacteria because of their higher affinity for such substrates.

6.   Sulphate reducing bacteria were never detected, and methane excretion was not affected by sulphate feeding.

7.   In conclusion, we have shown evidence for regulation of methanogenesis by dietary sulphate if sulphate reducing bacteria are present in the colon.

8.   The predominant sulphate reducing bacteria found in the gut belong to five genera, namely Desulfovibrio, Desulfobacter, Desulfomonas, Desulfobulbus and Desulfotomaculum.