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Hiren Korat
Dr. Zappi
NP 341-Science Dept. Seminar
6 November 2009
Helicobacter Pylori
The organism known as helicobacter pylori are bacteria associated with an organ once
thought to be uninhabitable to all bacteria; the human stomach. This bacteria is responsible for
causing numerous gastric disorders that range from inflammation to cancer. This bacterium is
the most widespread infection in the world affecting children and adults. It is capable of making
a sanctuary inside the stomach by using the enzyme urease to its advantage. There are treatments
available for infections, but H. pylori is not an easy antigen to eliminate. More research is
needed to be done to fully understand this organism.
Helicobacter pylori (H. pylori) was first discovered by Australian pathologist, Robin
Warren in 1982 (Press Release, 2005). He noticed in 50% of his patients in which biopsies were
taken a small curved bacteria had been colonizing in the lower part of the stomach (Press
Release, 2005). Warren observed that signs of inflammation were always present in gastric
mucosa, very close to where the bacteria were seen. Barry Marshall, a young clinical worker,
was interested in Warren’s findings and soon joined him in a study of 100 biopsies (Press
Release, 2005). Marshall had success in cultivating the unknown bacteria and both men were
able to determine in practically all biopsies, which contained the organism involved in gastric
inflammation, duodenal or gastric ulcers.
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Warren and Marshall had made a pioneering discovery at the time. Before their findings,
peptic ulcers could be healed by inhibiting gastric acid production. However, this was only a
temporary solution, as the ulcers would often relapse since the bacteria and inflammation
remained in the stomach. The men proved that the illness can be cured by eradicating the
bacteria from its environment by the use of antibiotics (Press Release, 2005). Warren and
Marshall had won the Nobel Prize in Physiology or Medicine for their findings.
H. Pylori is a spiral-shaped, gram negative bacteria, which is capable of thriving in the
human stomach, a very acidic environment. It is present in 50% of the world’s population, but is
mostly present in those people of developing countries (H. pylori, 2006). The bacteria is usually
obtained at an early age and usually picked up from the mother or unclean water supply. It can
remain in a person’s stomach for the rest of his or her life. It is about 3 micrometres in length,
with a diameter of about 0.5 micrometres. It is a microaerophilic organism, meaning that it
requires oxygen to survive, similar to aerobic bacteria. However, they are able to survive with
oxygen levels available at lower concentration than is found in the atmosphere. In fact, it does
not tolerate high oxygen conditions, but it requires at least 2% O2 (Pathogenesis, 2006). This is
because H. pylori uses oxygen as a terminal electron acceptor. H. pylori cannot utilize alternative
electron acceptors, such as nitrate or formate. It contains hydrogenase, which can be used to
obtain energy by oxidizing molecular hydrogen (H2) that is produced by intestinal bacteria
(Molecular 2002). H. pylori’s physical characteristics are key in its survival in the stomach.
There are usually four to six flagella at the end of the bacteria (Peptic Ulcer, 2007). This,
coupled with its spiral shape, help it move through the mucosa layer of the stomach easily. The
microbe is known as a neutrophile, which is an organism that lives in neutral pH (Helicobacter,
2006). Since the stomach is naturally an acidic environment, H. Pylori needs to make its
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environment more basic. It does this by secreting urease. Urease is a special enzyme that
catalyzes the hydrolysis of urea into both carbon dioxide and ammonia. The catalytic reaction
occurs as follows:
(NH2)2CO + H2O → CO2 + 2NH3
In 1926 James Sumner showed that urease is a protein. Urease is found in bacteria, yeast
and several higher plants. The pH-gated urea channel, UreI, is used to enhance urea access to
intrabacterial urease and a membrane-anchored periplasmic carbonic anhydrase to regulate its
periplasmic pH to about 6.1 (Acid Acclimation, 2005). This is crucial for the bacteria’s survival,
since other neutrophiles cannot regulate their periplasmic pH and thus only transit the stomach.
In addition, neutrophiles, with the exception of H. pylori, cannot colonize and grow in this
environment (Helicobacter, 2006).
A common bacterium which is comparable to H. Pylori from a straight forward point of
view is the very well known Escherchia Coli, E. Coli for short. This anaerobic bacteria has been
studied so intensively, that scientists have identified its entire genome (Todar, 2008). Like H.
Pylori, E. Coli is also a gram-negative bacterium possessing flagella for motile functions. It too
prefers to be around neutral to more basic pH. It is most commonly found in the large intestine,
although it can be found outside a living host in contaminated food or water. Most strains of E.
Coli are harmless, but some strains are capable of causing bowel inflammation and ulcerative
colitis (Todar, 2008). Harmful strains can be treated with antibiotics, and when not treated
correctly, can also develop resistance. However, pathogenic E. Coli are much easier to treat due
to the basic environment where they reside.
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H. Pylori is closely related to the campylobacter species, such as C. Jejuni and C. Coli.
These bacterium are similar to H. Pylori in that they are motile, gram-negative, non-spore
forming rod shaped organisms (Campylobacters, 2007). Their flagellar structures are also
similar in that they are primarily composed of two flagellins, FlaA and FlaB (Campylobacters,
2007). Their hosts are normally cattle, swine, and birds. C. Jejuni is usually non-pathogenic, but
C. Coli is pathogenic and can cause Campylobacteriosis. This illness induces inflammation,
bloody diarrhea, or dysentery syndrome. Like H. Pylori, the campylobacter species can be
picked up by humans, however it is usually done so by contaminated food sources. These
bacterium, while rod shaped, they are not straight but curved or spiral. Also, they do not reside
in the lining of the gastric mucosa, but that of the jejunum, ileum, or the colon (Campylobacters,
2007). This is all relative to the species. They are treatable via antibiotics, although there are
