The Sinister Link Between Infectious Agents, Bacteria and Protozoa
In 1980, Tim Rowbotham, a microbiologist at the University of Bradford, made an extraordinary discovery about a tiny single-celled protozoa called Acanthamoeba. These organisms are ubiquitous, turning up almost anywhere there is liquid water. Since the 1950s they have been known to cause a number of rare diseases, mainly in humans with impaired immune systems.
What Rowbotham found was that they could be much more dangerous.
It had long been known that protozoa feed on bacteria, gradually munching through great mounds of these bugs. However, Rowbotham discovered that Legionella, the particularly nasty bacteria that causes Legionnaire’s disease, could not only survive being eaten by Acanthamoeba but actually thrived on it. In fact, it turns out that there is some kind of symbiotic relationship between these organisms that even today is not yet fully understood.
Microbiologists are still coming to terms with the implications of this discovery. They have since found that Acanthamoeba can host other nasties too such as H Pylori, the bacteria responsible for stomach ulcers, various strains of the food poisoning bugs Lysteria and E coli, a type of Chlamydiae and MRSA, the superbug currently sweeping through many hospitals.
The fear is that Acanthamoeba harbours these bacterial species, providing a safe haven against attack from antibiotics and contributing to the virulence of these bugs. That could make them an important source of infectious disease that is largely ignored.
So the study of the interaction between Acanthamoeba and the bacteria it supports has become an important area of research. But it is hampered by the difficulty of studying how protozoa interact with bacteria.
Today, Giorgos Tsibidis from the Foundation for Research and Technology in Greece and a couple of mates make a contribution that could help. It takes the form of a computer vision system that can identify individual protozoa, distinguishing them from cysts by virtue of their shape, and follow them as they move. The same system is also able to monitor concentration of bacteria.
They’ve tested the idea by watching the behaviour of Acanthamoeba protozoa grazing on a lawn of Salmonella bacteria. The machine is able to follow the Acanthamoeba as they move and to measure the drop in concentration of the Salmonella bacteria is they are eaten.
That’ll save some postdocs a huge amount of time and could dramatically improve our understanding of protozoan-bacterial interactions. it may even help save a few lives if it turns out that Acanthamoeba play a significant role in the transmission of disease.
Ref: arxiv.org/abs/1008.4662: Automated Two-Dimensional Acanthamoeba Polyphaga Tracking And Calculation Of Salmonella Typhimurium Distribution In Spatio-Temporal Images
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