Role of Intestinal Microbiota in Ulcerative Colitis

Introduction and objectives
Introduction and objectives
Since the beginning of the last century from the early work of Elie Metchnikoff, it is believed that a
synergistic interaction exists between intestinal microbes and their host.
Metchnikoff observed that:
“… different susceptibilities of people to the harmful action of microbes and their products. Some
can swallow without any evil result a quantity of microbes which in the case of other individuals
would produce a fatal attack of cholera. Everything depends upon the resistance offered to the
microbes by the invaded organism" (Metchnikoff, 1908).
Hence, an unfavorable composition of the gut microbiota could play a role in intestinal infections
and diseases. Consumption of indigestible carbohydrates or dietary fibers is suggested to improve
gut health by modulating the gut environment through selective stimulation of bacteria who are
able to promote beneficial events in the host by inhibition of pathogenic bacteria, and induction of
immune regulatory functions (Vernazza et al., 2006).
The objectives of this thesis were to investigate, if the gut microbiota and its ability to colonize
mucus are different in patients suffering from the intestinal bowel disease, ulcerative colitis (UC)
than in healthy subjects, hence playing a role in colonic inflammation. Additionally, investigate the
ability of novel indigestible carbohydrates or fibers from sugar beet and potato pulp to induce
beneficial changes in fecal microbiota communities in vitro obtained from human volunteers both
healthy and UC patients.
The first part of this thesis gives a theoretical introduction to the phylogenetic composition of the
human intestinal microbiota, the location of the microbiota within the colon and their interactions
with the host. Additionally, UC and the colonic microbiota composition observed in UC patients
will be described. Finally, modulation of the intestinal microbiota by prebiotics will be addressed
together with a description of the production of prebiotics and novel carbohydrates. The second
part contains a description of the methodologies used in the studies of this thesis and six papers
that demonstrate the experimental work. The last part is discussion and conclusion based on the
theoretical and experimental work of this thesis.
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