By some estimates, Helicobacter pylori (H. pylori) causes the most widespread an

Question

By some estimates, Helicobacter pylori (H. pylori) causes the most widespread and common infection in the world. Over half the people in the world have H. pylori, a bacterium, inhabiting their stomachs. Given these statistics, it is surprising that most people have never heard of H. pylori. The fact that the majority of people infected with H. pylori never show signs of infection probably accounts for its lack of recognition in the general public. However, those who do experience complications from H. pylori are at a much higher risk for stomach cancer and ulcers. Since H. pylori is associated with such serious stomach diseases, there is a great deal of interest in studying the bacterium.

That H. pylori chooses the stomach as its home makes it somewhat unique among bacteria. The stomach represents a quite inhospitable environment for most bacteria. However, H. pylori has evolved a variety of unique features to help it thrive in the stomach. H. pylori has a collection of powerful flagella, whip-like extensions that help the bacteria move and swim. H. pylori can sense chemical gradients and it typically chooses to inhabit the pyloric antrum, where it encounters relatively few parietal cells. The bacterium then uses adhesin proteins on its surface to stick to the stomach's epithelial cells. Once H. pylori has settled in the stomach, its chemical activities stimulate G cells to release gastrin into the blood. As the bacteria reproduce and stimulate more and more gastrin production, a positive feedback loop begins that might irritate and damage the digestive tract. Biologists think this series of events might explain some of the serious gastrointestinal problems associated with H. pylori.

1. Why do you think H. pylori requires powerful flagella and adhesin surface proteins to survive in the stomach?

2. Why would H. pylori prefer to settle in areas of the stomach with relatively few parietal cells?

3. Describe the mechanisms by which the positive feedback loop described above could eventually cause damage to digestive organs.

Explanation / Answer

By some estimates, Helicobacter pylori (H. pylori) causes the most widespread an

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