Bacteria living in the human colon can survive on dietary fiber as their only source of food 107th General Meeting of the American Society for MicrobiologyMay 21-25, 2007, Toronto, Ontario, Canada
For more information on any presentation at the 107th General Meeting of the ASM contact Jim Sliwa, ASM Office of Communications at jsliwa@asmusa.org
EMBARGOED UNTIL: Tuesday, May 22, 9:00 AM EDT(Session 041/I, Paper I-030)JakobKirchnerHyperion Biotechnology, Inc.Brooks City-Base, TX, United States
We have found that a small subpopulation of bacteria found in the human colon can rapidly proliferate when given dietary fiber as their only sugar source. The bacterial composition of the colon is an important determinate of GI health. Our findings link consumption of dietary fiber, known to promote good health, with preferential growth of specific microorganisms. We show that feeding bacteria dietary fiber from human supplements causes enrichment for specific, beneficial, bacteria in a test tube, presumably this also occurs in the human gut.
Hyperion Biotechnology, Inc. of San Antonio, Texas and Mannatech™, Inc. of Coppell, Texas have discovered that the bacteria present in the human colon can readily consume Mannatech’s dietary supplement Advanced Ambrotose™ and twoof its fiber components. Dr Jakob Kirchner and Dr. Cherie Oubre from Hyperion have found that some bacteria from the human colon proliferate rapidly when fed a diet composed solely of these dietary fibers.
The experiment consisted, first, of collecting feces from four people with a history of excellent GI health. A small portion of a fecal sample was then added to a salt solution that contained Advanced AmbrotoseTM or one of its component polysaccharides obtained from the bark of the Larch tree (a fiber polysaccharide called arabinogalactan), Aloe Vera gel, a preparation widely used by inflammatory bowel suffers, or a complex dietary supplement containing both arabinogalactan and Aloe Vera gel along with other components.
The three fiber polysaccharides were subjected to dialysis prior to use to remove molecules smaller than 10,000. This is important because many bacteria have the capability of using small sugars and other small molecule and our focus is to identify bacteria that are able to use the large molecules that make up complex dietary fibers. The cultures of fecal bacteria and specific fiber sources were placed in an oxygen-free (anaerobic) environment heated to body temperature, which simulates the environment found in the GI tract.
After three days a small amount of the culture was transferred to a clean flask that contained a fresh stock of the salt solution with the polysaccharide. Three days after this, the process was once again repeated. After 9 days the chemical composition of the liquid portion of the culture was evaluated by Dr. Robert Sinnott’s group at Mannatech. The chemical evaluation consisted of comparing the polysaccharide composition after incubation with the fecal bacteria to a control that was incubated for the same period of time in the salt solution. The chemical evaluation showed that bacteria consume polysaccharides across the entire molecular weight range from 10,000 to 1,000,000.
Somewhat surprisingly, Dr. Sinnott observed an increase in molecules less than 10,000. Since molecules of this size had been removed from the original material by dialysis, we hypothesize that the bacteria may export enzymes that break up the large polysaccharides into small sugars making them easier to use. The use of the very large molecules may mean that bacteria ingest whole particles of fiber, break them down and use them for energy. Another possibility is that glycosidases are exported and that these enzymes are responsible for breaking down the very large fiber molecules. Drs. Kirchner and Oubre characterized the bacteria using DNA sequencing with comparison of the sequence to published databases and classical microbiological methods that characterize the biochemical capability of bacteria.
The results show that out of 57 microorganisms isolated from these cultures, only six species were present. Of these six, 80% of the species identified were determined to be Eneterococcus faecium. This shows that a common GI tract bacteria is readily able to digest fiber and proliferate. This suggests that feeding of fiber may have an important impact on the composition of the bacteria present in the GI tract. Bacteria in the GI tract have recently been shown to be directly implicated in obesity and are probably responsible for other elements of human health. Altering the relative abundance of bacterial species in the GI tract by consuming fiber maybe important. Dietary fiber may have health effects that far exceed those that we associated just with forming bulk in the colon.
What is the impact of the research? Everyone knows that a healthy diet should include dietary fiber from plants. Many fiber products are semi-synthetic meaning they are obtained from a natural source like wood and then modified chemically to make them easier to suspend in water. An example is hydroxypropylmethyl cellulose, the major ingredient found in many of the dietary supplements. These semi-synthetics pass through the GI tract virtually unchanged. We have shown that fiber from Larch tree bark and Aloe Vera gel can be broken down and used by a relatively small number of bacteria.
Our results suggest that some bacteria can use the fiber quite well for the purpose of making more bacteria. This means that regular ingestion of some types of plant fiber will change the relative abundance of bacterial species. A recent report (Nature, 2006 Dec 21;444(7122):1027-31) shows that obese people have a very different population of bacteria and capture more energy from their food then non-obese individuals. In mice, transfer of GI bacterial populations could transform obese mice into healthy mice and visa versa.
Our findings suggest that regular use of some types of dietary fiber may be able to cause a similar switch in microbial populations. If this could be achieved, a safe and effective way of loosing weight may be at hand. Other effects of these dietary fiber-consuming bacteria could also be important. When the bacteria consume polysaccharides under anaerobic conditions like those present in the gut, they produce small chain fatty acids. These have been shown to have beneficial effects on GI health. Some polysaccharides, notably Aloe Vera, have been shown to be effective in treating some types of GI tract disorders.
Hyperion scientists have recently discovered (unpublished results) that some forms of Aloe Vera gel are able to stimulate the immune system but that other forms cannot. Some types of fiber may be very important in building and maintaining a good immune response against pathogenic bacteria. Stated simply, not all fiber is equal with regard to impact on health and wellness.
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