host-microbe interaction

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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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A Case of the Missing Microbes

Most animals depend on their gut microbes for digestive help. The caterpillar, however, seems to lack resident gut microbes all together.

By characterizing the microbial composition across 124 species of caterpillars from North America and Costa Rica, Tobin Hammer and colleagues at the University of Colorado Boulder found that caterpillars do not have microbial friends living in their gut. Fecal material from the caterpillars contained several orders of magnitude fewer microbes compared to other organisms. (more…)

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A Bacterium You Can See With the Naked Eye

It is commonly believed that bacteria are microscopic – stealthy and hidden from the naked eye. But the bacterium, Epulopiscium fishelsoni, is a microbial behemoth you can see with the human eye alone. First discovered in the intestines of a brown surgeonfish in the Red Sea in 1985, this giant bacterium was first classified as a protist because of its large size. In 1993, rRNA sequencing revealed that this organism is actually a bacterium.

Epulopiscium varies between 10- to 20-fold in length and has a volume more than 2,000 times that of a typical bacterium. They range from 200 - 700 microns in length, about the size of a grain of table salt. But being big does have its downsides. (more…)

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Think again before you compost that

Spring has arrived, gardens are planted, and now, we eagerly await the harvest of fruits and vegetables. This spring awakening brings not only new plant life, but fungi also come out to feast. Phytophthora root rot is a common fungal disease in plants, infecting over 250 plant genera including peppers, tomatoes, berries, and eggplants. At least a hundred species of fungi are responsible for phytophthora root rot. Chemical efforts to treat phytophthora root rot have been ineffective to control disease and have mostly been banned. So what is a gardener or farmer to do? (more…)

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Eaten alive from the inside: predatory bacteria kill pathogenic bacteria from the inside out

When it comes to predators, we naturally think of large, agile, and powerful animals on the prowl. But we often don’t think about the most abundant predators on our planet, predators of the microscopic world. In the depths of the microbial universe, predatory bacteria (those that feast upon other bacteria) have emerged. These bacteria are now ubiquitous in terrestrial and marine environments. Predatory bacteria penetrate the outer membrane of bacterial prey and ingest their prized nutrients, killing the prey. (more…)