11.   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.

12.   Quantitative measurements show that in methanogenic subjects the majority of gaseous hydrogen produced from fermentation is consumed by methanogenic bacteria.

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

14.   When sulphate availability is limited, methanogenic bacteria may then predominate.