From Alzheimer’s to Zebrafish: Eclectic Science and Regulatory Stories 92
Bacteroides thetaiotaomicron is the prominent and remarkable bacterial species in the
distal intestinal tract of adult humans. It is a very successful anaerobic glycophile (“sugar
loving” microbe) whose prodigious capacity for digesting otherwise indigestible dietary
polysaccharides is reflected in its genome. It encodes 241 glycoside hydrolases and
polysaccharide lyases. This means that the organism has the ability to break down xylan-,
pectin- and arabinose-containing polysaccharides that are common components of dietary
fiber.26 When dietary polysaccharides are scarce, B thetaiotaomicron turns to host mucus by
deploying a different set of polysaccharide-binding proteins and glycoside hydrolases.
Other Bacteroides species include B vulgatus, B distasonis, and B fragilis. All play a role in the
digestive process.
New Research
Microbiologists from Louis Pasteur (1822–95) and Ilya Mechnikov (1845-1916) to present-
day scientists have emphasized the importance of understanding the contributions of
our microbiota to human health and disease. Mechnikov, who won the Nobel Prize for
Physiology and Medicine in 1908, was one of the first researchers to study the flora of the
human intestine.27 He developed a theory that senility is due to poisoning of the body
by the products of these bacteria. To prevent them from multiplying, he suggested a diet
containing milk fermented by bacilli, which produce large quantities of lactic acid.28
Today, science is on the verge of understanding how the body maintains a state
of equilibrium with its incredibly complex enteric microflora.29 Appropriate immune
recognition is also essential to host-bacteria symbiosis (i.e., the biological association of
two individuals or populations of different species). It has recently been shown that the
recognition of commensal bacteria by epithelial cells protects against intestinal injury.30
Other research indicates that use of antibiotics reduces the capacity of intestinal micro-
flora to metabolize phytochemicals into compounds that may protect against cancer.31
However, antibiotic use also disrupts the intestinal microflora metabolism of estrogens,
which results in lower levels that might decrease the risk of some hormonal cancers. Use
of antibiotics may be associated with cancer risk through effects on immune function and
inflammation, although little is known about these mechanisms.32,33
Intestinal bacteria release chemical signals recognized by specific receptors—called
“toll-like receptors” (TLRs)—of the innate immune system. The interaction helps to
maintain the architectural integrity of the intestinal surface and enhance the ability of
the epithelial surface to withstand injury. A deficiency in any of the numerous signaling
molecules can induce intestinal inflammation, which may be a precursor of inflammatory
bowel disease. Research is now ongoing to understand various types of TLR activation
to ascertain how this information can be used to treat irritable bowel syndrome, Crohn’s
disease and other types of intestinal inflammatory conditions.34
A group of medical researchers in Ireland recently identified five probiotic bacte-
ria than can prevent Salmonella infection in pigs and, if translated to humans, could
potentially reduce Salmonella-induced foodborne illnesses, which cause between 500
and 1,000 deaths every year in the US.35 This same group is also investigating the human
microbiome for antimicrobials against pathogens. They have isolated a compound called
lacticin 3147 from the harmless bacterium Lactococcus lactis, which is used to make cheese.
Recently, lacticin 3147 has demonstrated antimicrobial activity against a range of geneti-
cally distinct Clostridium difficile strains isolated from the human gut. This indicates that
lacticin 3147 may offer a new treatment for C difficile-associated diarrhea, a serious condi-
tion that affects 3,000,000 people per year in the US and is a major problem in hospitals.36
There is evidence confirming the effects of Lactobacillus GG in preventing diarrhea
and atopy in children.37,38 These organisms are thought to occupy binding sites in the gut
mucosa and prevent pathogenic bacteria from adhering. Lactobacilli also produce bacte-
riocins that act as local antibiotics. Diarrhea associated with antibiotics may result from
Bacteroides thetaiotaomicron is the prominent and remarkable bacterial species in the
distal intestinal tract of adult humans. It is a very successful anaerobic glycophile (“sugar
loving” microbe) whose prodigious capacity for digesting otherwise indigestible dietary
polysaccharides is reflected in its genome. It encodes 241 glycoside hydrolases and
polysaccharide lyases. This means that the organism has the ability to break down xylan-,
pectin- and arabinose-containing polysaccharides that are common components of dietary
fiber.26 When dietary polysaccharides are scarce, B thetaiotaomicron turns to host mucus by
deploying a different set of polysaccharide-binding proteins and glycoside hydrolases.
Other Bacteroides species include B vulgatus, B distasonis, and B fragilis. All play a role in the
digestive process.
New Research
Microbiologists from Louis Pasteur (1822–95) and Ilya Mechnikov (1845-1916) to present-
day scientists have emphasized the importance of understanding the contributions of
our microbiota to human health and disease. Mechnikov, who won the Nobel Prize for
Physiology and Medicine in 1908, was one of the first researchers to study the flora of the
human intestine.27 He developed a theory that senility is due to poisoning of the body
by the products of these bacteria. To prevent them from multiplying, he suggested a diet
containing milk fermented by bacilli, which produce large quantities of lactic acid.28
Today, science is on the verge of understanding how the body maintains a state
of equilibrium with its incredibly complex enteric microflora.29 Appropriate immune
recognition is also essential to host-bacteria symbiosis (i.e., the biological association of
two individuals or populations of different species). It has recently been shown that the
recognition of commensal bacteria by epithelial cells protects against intestinal injury.30
Other research indicates that use of antibiotics reduces the capacity of intestinal micro-
flora to metabolize phytochemicals into compounds that may protect against cancer.31
However, antibiotic use also disrupts the intestinal microflora metabolism of estrogens,
which results in lower levels that might decrease the risk of some hormonal cancers. Use
of antibiotics may be associated with cancer risk through effects on immune function and
inflammation, although little is known about these mechanisms.32,33
Intestinal bacteria release chemical signals recognized by specific receptors—called
“toll-like receptors” (TLRs)—of the innate immune system. The interaction helps to
maintain the architectural integrity of the intestinal surface and enhance the ability of
the epithelial surface to withstand injury. A deficiency in any of the numerous signaling
molecules can induce intestinal inflammation, which may be a precursor of inflammatory
bowel disease. Research is now ongoing to understand various types of TLR activation
to ascertain how this information can be used to treat irritable bowel syndrome, Crohn’s
disease and other types of intestinal inflammatory conditions.34
A group of medical researchers in Ireland recently identified five probiotic bacte-
ria than can prevent Salmonella infection in pigs and, if translated to humans, could
potentially reduce Salmonella-induced foodborne illnesses, which cause between 500
and 1,000 deaths every year in the US.35 This same group is also investigating the human
microbiome for antimicrobials against pathogens. They have isolated a compound called
lacticin 3147 from the harmless bacterium Lactococcus lactis, which is used to make cheese.
Recently, lacticin 3147 has demonstrated antimicrobial activity against a range of geneti-
cally distinct Clostridium difficile strains isolated from the human gut. This indicates that
lacticin 3147 may offer a new treatment for C difficile-associated diarrhea, a serious condi-
tion that affects 3,000,000 people per year in the US and is a major problem in hospitals.36
There is evidence confirming the effects of Lactobacillus GG in preventing diarrhea
and atopy in children.37,38 These organisms are thought to occupy binding sites in the gut
mucosa and prevent pathogenic bacteria from adhering. Lactobacilli also produce bacte-
riocins that act as local antibiotics. Diarrhea associated with antibiotics may result from