helicobacter pylori

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Happy Birthday Robert Koch!

On this date in 1843, Robert Koch, the founder of modern microbiology was born.  And on December 10, 1905, one day before his 62nd birthday, he was awarded the Nobel Prize in Physiology or Medicine for his work on tuberculosis.

But what many microbiologists are more familiar with are the Koch’s postulates, four criteria needed to establish a causal relationship between microbe and disease. These are:

  • The microorganism must be found in individuals suffering from the disease, but in not healthy individuals,
  • The microorganism must be isolated from a diseased individual and grown in pure culture,
  • The cultured microbe should cause disease when introduced into a healthy individual, and
  • The microbe must be isolated from the inoculated individual and identified as the same microbe from the original source.

Now, more than a century after Koch’s time, how do these postulates hold up? (more…)

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Meet a microbiologist: Stéphane Benoit

Many graduate students call the lab their second home. I was fortunate enough to have a second “lab home”. Today, we meet Stéphane Benoit, a microbiologist from my second “lab home” who has taught me much of what I know about working with the stomach bacterium Helicobacter pylori.

Growing up in the French village of Saint Pierre La Palud near Lyon, Stéphane has spent countless hours observing the social behavior of ants in the woods. He has always been interested in the sciences, especially biology. After obtaining his Ph.D. from the National Institute of Applied Sciences of Lyon, Stéphane came to the United States for what he thought was a two-year postdoc to study metal utilization in spirochetes at the University of Georgia. (more…)

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Microbes in costumes trick the immune system

Halloween has finally arrived and everyone around you has been busy working on their costumes in anticipation for this glorious day of tricks and treats. Come Halloween night, you may not even recognize the faces behind the costumes. How would you tell apart friends with a sweet tooth from foes ready for some tricks?

For some bacteria, putting on costumes is an everyday event when it comes to tricking the immune system. The immune system distinguishes the body's own cells from those of invading bacteria and viruses. Since the microbe's outer membrane is usually the first thing the immune system sees, the body takes advantage of molecules found on the outer membrane to generate an immune response. This seems like a wise defense mechanism but microbes have several tricks up their sleeves; they disguise themselves from the immune response by changing molecules on their outer membrane (antigenic variation) or by turning on and off expression of genes encoding for surface molecules (phase variation). (more…)

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Microbe of the month: Helicobacter pylori

The first Microbe of the Month is Helicobacter pylori, my favorite bacterium during my graduate school years.

Discovery of Helicobacter pylori

Stomach ulcers were traditionally thought to be caused by stress. However, in 1982 Barry Marshall and Robin Warren discovered that the bacterium Helicobacter pylori (H. pylori for short) is actually the cause of these ulcers. These scientists found that almost all stomach biopsies from patients with gastric ulcers also contained this helical shaped bacteria (hence the name Helicobacter). Barry and Marshall's discovery was met with much skepticism at the time. Desperate to prove that H. pylori was indeed the cause of gastric ulcers, Marshall drank a culture of H. pylori and developed gastric ulcers that were accompanied by H. pylori in his gastric biopsies. He then cured himself of the infection by taking antibiotics. For this discovery Marshall and Warren were awarded the Novel Prize in Physiology or Medicine in 2005. (more…)