The Zoonotic and Animal Pathogens Research Laboratory at the University of Edinburgh has worked with a UK-based animation company to produce a full-length animation representing the key stages of E. coli O157:H7 interaction within the gastrointestinal tract. This movie was featured in the August 2004 issue of Microbiology Today, published by the Society for General Microbiology.
Cyanobacteria are the oldest bacteria, having evolved around 3.8 billion years ago. The ability of cyanobacteria to perform oxygenic photosynthesis is thought to have converted the early reducing atmosphere into an oxidizing environment which dramatically changed the life forms on Earth and provoked an explosion of biodiversity. And they’re still here:
Around the year 1590, two Dutch spectacle makers, Hans and Zaccharias Janssen were experimenting with glass lenses. They put several lenses in a tube and discovered that an object near the end of the tube could be viewed at much larger magnification than a simple magnifying glass could achieve. This was the invention of the microscope.
In 1648 while working for a cloth merchant in Amsterdam, Antonie van Leeuwenhoek saw his first simple microscope, which was only capable of magnifying a few times but was useful for counting the threads in cloth. He acquired a microscope for his own use and became so interested that he went on to learn how to make his own lenses.
During his lifetime van Leeuwenhoek ground more than 500 optical lenses and created over 400 microscopes, only nine of which still exist today. His microscopes consisted of silver or copper frames rather than a tube to hold the lenses. By grinding and polishing, he was able to make small lenses with large curvatures. These fat lenses produced greater magnifications, and his microscopes were eventually able to magnify up to 270 times. Van Leeuwenhoek never published his method of how to make these superb lenses.
Robert Hooke also spent much of his life working with microscopes and improved their design. In 1664 he published a book entitled Micrographia in which he described and illustrated small insects such as fleas, but which also contained the first description of plant cells. It is believed that van Leeuwenhoek read Hooke’s book in 1665 and that this stimulated him to use his microscopes for the purpose of investigating the natural world.
In 1674 van Leeuwenhoek discovered protists (which he called animalcules from the Latin for “little animal”) in lake water, and in 1676 was the first person to observe bacteria scraped from the film between his own teeth. In 1677 he also became the first person to observe spermatozoa. But van Leeuwenhoek’s work went far beyond merely observing micro-organisms. For example, in 1676 he described his methods of making infusion cultures of micro-organisms (so the next time anyone tries to tell you Louis Pasteur was the “Father of Microbiology”, remind them that van Leeuwenhoek got there 200 years earlier!).
Van Leeuwenhoek began to send of his microscopic observations to the Royal Society in England, and in 1676 he sent his first observations of microscopic single celled organisms. Such was the quality of his microscopes that other scientists were initially unable to repeat his observations, and his credibility was questioned. Eventually, in 1680, van Leeuwenhoek’s work was accepted by the Royal Society.
Thonis Leeuwenhoek (16321723), was born and died in Delft in The Netherlands, and was known in his adult life as Antonie. He adopted “van” to precede his surname as a mark of social status in 1686.
The Chlamydia are a genus of obligate intracellular bacteria. There are only a few species in this genus and Chlamydia trachomatis is the one which causes sexually transmitted infections in humans. Chlamydia is the most common sexually transmitted infection in the UK and probably worldwide. In developing countries, Chlamydia infection of the eye is the most common cause of preventable blindness. The UK national screening programme has found that 10% of both men and women aged 18 to 25 carry the bacterium, and the Health Protection Agency says that cases of Chlamydia infection have increased by more than 200 per cent in England in the past decade.
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Chlamydia infections of the genital tract frequently show no symptoms at all, particularly in women, and so may go untreated for years. For a long time, chronic infection has been known to harm fertility in infected women, but it has recently been shown that infected men also have decreased fertility. This was demonstrated when a team of doctors from Mexico examined sperm from men infected with Chlamydia who had failed to father a child. Using a microscopic analysis technique, they found the level of DNA fragmentation in their sperm was more than three times higher than in healthy men. The concentration of their sperm, and its ability to swim were also poor, and there were increased levels of defects in sperm shape. The researchers then treated 95 of the infertile men with antibiotics effective against Chlamydia and found the DNA sperm damage improved by an average of 36% after four months. During that period, 13% of the couples became pregnant but after the treatment was finished, 86% achieved a pregnancy.On the BBC website, Dr Allan Pacey, Secretary of the British Fertility Society, is quoted as saying that more needs to be done to target the younger generation.
The message is that we might think of Chlamydia as a disease that damages female fertility, but we need to think again. Chlamydia is getting out of control. We have got to encourage men as well as women to go for screening, but men are more reluctant to do this if they don’t have symptoms. It is the 18 to 25 age group that is of most concern. There should be a page on Facebook you can log onto and sort screening out.
Unlike some of the sexually-transmitted diseases discussed on MicrobiologyBytes (e.g. HIV infection, which is a pretty good reason not to have unprotected sex), Chlamydia infections are easy to treat with a short course of antibiotics - if they can be diagnosed. Because of the unusual intracellular lifestyle of the bacterium, conventional microbiological culture methods are of limited use in detecting the organism. In recent years, techniques involving DNA amplification have become the mainstream diagnostic method.
Here is tale of brave microbiologists on the trail of the most fabulous beast in the prokaryotic kingdom. The saga of Helicobacter pylori is one to rival the early feats of Pasteur, Koch and Beijerinck.
Helicobacter pylori is a helical Gram-negative bacterium which infects the stomach and duodenum. Many people who are infected with this microbe do not show any symptoms of disease, but in other cases a lifetime of infection can lead to peptic ulcers, gastritis and perhaps stomach cancer.
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In the 19th century, German and Italian scientists described helical bacteria in the lining of the stomach of humans and dogs, but because they could not be grown in culture, they were eventually forgotten. These organisms were rediscovered at the end of the 1970s by Australian doctors Robin Warren and Barry Marshall. In a controversial paper, Warren and Marshall argued that most stomach ulcers and gastritis were caused by infection by this bacterium and not by stress or spicy food as had been assumed previously (Unidentified curved bacilli in the stomach patients with gastritis and peptic ulceration. Lancet 1984 8390: 1311-1315). The idea that this bacterium could cause stomach ulcers was met with a great deal of scepticism. Eventually, Barry Marshall deliberately swallowed a culture of the bacterium (don’t try this at home). A week later, he began to suffer acute symptoms of gastritis, and stomach biopsies revealed that he had become infected with H. pylori and showed severe acute gastritis. Marshall wrote:
Becoming increasingly frustrated with the negative response to my work I realized I had to have an animal model and decided to use myself. Much has been written about the episode and I certainly had no idea it would become as important as it has. I didn’t actually expect to become as ill as I did. I didn’t discuss it with the ethics committee at the hospital. More significantly, I didn’t discuss it in detail with Adrienne [his wife]. She was already convinced about the risk of these bacteria and I knew I would never get her approval. This was one of those occasions when it would be easier to get forgiveness than permission. I was taken by surprise by the severity of the infection. When I came home with my biopsy results showing colonization and classic histological damage to my stomach, Adrienne suggested it was time to treat myself. I had a successful infection, I had proved my point.
Fortunately, Marshall was able to cure himself with a course of multiple antibiotics, which is now the standard therapy for Helicobacter infection. In spite of this dumb stunt, the 2005 Nobel Prize in Physiology or Medicine was awarded to Marshall and Warren“for their discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease”.
Unfortunately, an increasing number of infected individuals are found to harbour antibiotic-resistant strains of Helicobacter. This results in initial treatment failure and requires additional rounds of antibiotic therapy or alternative strategies such as a quadruple therapy (treatment for four antibiotics).
Helicobacter species are one of the few known microorganisms which can not only survive but thrive in the highly acidic environment of the stomach. The helical shape of the organism may help penetration of and motility in the mucus gel layer which protects the body from stomach acids. In addition, the bacteria produce a large amount of urease, an enzyme that breaks down urea into ammonia and carbon dioxide and forms a protective alkaline layer around them. This discovery enabled Marshall to develop a non-invasive breath test: patients swallow a small amount of urea labeled with a carbon isotope, and if H. pylori are present, the urea is broken down to release mildly radioactive carbon dioxide in the breath. As this is much more fun than having a stomach biopsy, this has become a common way of diagnosing H. pylori infection.
So that’s the saga of Helicobacter pylori. Because we could not grow it in the laboratory, we pretended it did not exist. It took a man with a strong stomach to show us the error of ignoring this unusual organism.
