Nutritional Aspects of Dissimilatory Sulfate Reduction in the Human Large Intestine |
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Authors: | Caroline L Willis John H Cummings Graham Neale Glenn R Gibson |
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Institution: | (1) Institute of Food Research, Earley Gate, Reading, UK , GB;(2) Medical Research Council Dunn Clinical Nutrition Centre, Hills Road, Cambridge, UK , GB;(3) Department of Gastroenterology, Addenbrooke's Hospital, Cambridge, UK , GB |
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Abstract: | In contrast to other anaerobic ecosystems, such as marine and estuarine sediments, there is a lack of information on the
nutritional requirements of human gut sulfate-reducing bacteria (SRB). Various substrates stimulated sulfate reduction in
mixed culture, including short-chain fatty acids and other organic acids, alcohols, and amino acids (but not sugars or aromatic
compounds). However, the use of sodium molybdate as a specific inhibitor of sulfate reduction caused an accumulation of ethanol
and malonate only, and reduced the rate of utilization of lactate. This indicates the importance of these electron donors
for sulfate reduction. Since ethanol and lactate are primarily utilized by members of the Desulfovibrio genus, the results suggest a physiologically important role for this group. Experiments with two strains of Desulfovibrio desulfuricans isolated from human feces demonstrated that both were able to reduce sulfite, thiosulfate or nitrate in the absence of sulfate.
In addition, one strain (DsvUC1) was able to grow by fermentative metabolism, although the second strain (DsvFD1) showed more
restricted fermentative growth. The data indicate that desulfovibrios are ecologically the most significant group of SRB in
the human colon, and that colonic isolates belonging to this genus are versatile, in terms of both the electron acceptors
and donors that they are able to utilize.
Received: 24 March 1997 / Accepted: 10 June 1997 |
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