Archive for June 2011
Last week I had the pleasure of attending an event mixing craftwork with bacteriology. It sounds like an odd combination, but was in fact the latest in a series of outreach events organised by Science London.
Joining 50 other people in London’s Drink, Shop & Do cafe, I arrived with my pals from the British Science Association to find tables festooned with felt, thread, and glitter. Our task was to create a bacterium from what was available to us. You can see some of our efforts in the photos below; mine is the expertly crafted blue circle with glued-on eyes and multi-coloured flagella. Prizes were available for the best creation. I did not win a prize. The winner did use some purple thread to Gram-stain his effort, which I thought was rather clever.
In addition to the craft, there was a quiz all about microbiology. I did not win the quiz. I got over my embarrassment with the aid of
G&T pecan pie, so all was well…
I’m pretty lucky to work at the Wellcome Trust. We always have excellent events about science or the history of medicine. This month was no different. I went to the first in a series of talks held at Wellcome Collection called ‘The Thing Is…’, hosted by Quentin Cooper from Radio 4′s Material World. The event invites a guest speaker to describe the history behind a single object found within Wellcome Collection’s vast archives.
Our speaker this month was Hugh Pennington, emeritus professor of bacteriology at the University of Aberdeen. The object he chose to describe was a device for spraying carbolic acid, dating back to around 1875, designed by Joseph Lister. Professor Pennington used the machine to describe the history of antisepsis, early microbiology and surgery.
Tuberculosis is the world’s oldest and most deadly disease. It’s caused primarily by Mycobacterium tuberculosis, which is commonly known as the tubercle bacillus, or TB. Despite the advent of antibiotics nearly 100 years ago, an estimated two billion people are infected with TB and tuberculosis kills around two million people every year. Drug tolerance in TB, after it has infected humans, appears to be key to its success.
Now it seems we are beginning to understand how this works. In a recent paper published in the journal Cell, Lalita Ramakrishnan and colleagues report that Mycobacterium marinum bacteria infecting zebrafish embryos respond to antibiotic treatment in an exactly the same way as M. tuberculosis bacteria infecting humans. Because M. marinum is 99% identical to TB genetically and infects transparent zebrafish embryos, it is an excellent model for studying tuberculosis. Tracking the M. marinum bacteria during infection and antibiotic therapy of the zebrafish shows that not all of the bacteria are killed by antibiotic treatment; some acquire drug tolerance and hide inside immune cells known as macrophages, then use these immune cells to spread around the body.
The Escherichia coli (E. coli) bacterium is commonly found in the guts of humans and other mammals. Most E. coli strains are harmless, but some – including enterohaemorrhagic E. coli (EHEC) – cause severe disease. EHEC is transmitted to humans primarily through consumption of contaminated foods, such as undercooked meat and unpasteurised milk1.
The recent EHEC outbreak in Germany is unusual because it was probably spread by salad leaves and has infected 2400 people, killed 24 and left many more with serious complications as a result of infection. Although the outbreak appears to have peaked, it raises a terrifying new spectre of drug-resistant, infectious bacteria being spread by something as seemingly innocuous as salad. It’s also pretty embarrassing for health ministers in Germany who wrongly pointed at Spanish cucumbers as the source of this new “superbug” and have been warned by the EU health minister not to issue any more premature – and false – health warnings 2.
In fact, reports that this is a completely new strain are incorrect3 and outbreaks of Salmonella– and E. coli-induced food poisoning caused by contaminated salads are also nothing new. The problem is that the bacteria can actually infect salad leaves, spinach, cucumbers and tomatoes so that washing them does not make them safe to eat. It seems this outbreak is not the start of something new: it’s happened before, and it’s pretty certain that it will happen again. Unless we start cooking our salads…
Back when I was a teenager devouring science fiction novels, I read a wonderful short story written in 1941 by Theodore Sturgeon, called “microcosmic gods.” Sturgeon’s god was Mr Kidder, an amateur scientist who had the great idea that – instead of trying to invent new products on his own – he could create his own fast-living species and they could invent for him, solving any problem that Mr Kidder could pose, if not within one generation, then in no more than two or three. Mr Kidder’s microcosmic civilisation invented, among other things, super-strong aluminium, a generator powered by cosmic energy, and an impenetrable force field.
The thing about science fiction is that it guesses right in unanticipated ways, and so, while we still don’t have any of those inventions, we do now have experimental evolution. Labs around the world regularly use microbes, which evolve quickly, to solve problems in evolutionary biology. One such example is given by Manhes and Velicer (2011), who show that a social bacterium, Myxococcus xanthus, can evolve to police cheaters within its own species.