Natural predators
In your body right now, microscopic hunters are on the lookout for prey, swimming at the human equivalent of hundreds of miles per hour. It might sound scary, but don't panic; these bacterial killing machines are not only completely harmless to human cells, but could be used as the next generation of medicines on a mission to kill antibiotic-resistant super-bugs.
Researchers at Nottingham's Institute of Genetics are one of only a handful of research groups in the world currently working on Bdellovibrio bacteria. With their European partners at the Max Planck Institute for Developmental Biology and the University of Bielefeld in Germany, they recently published the entire Bdellovibrio genome in the journal Science. It's early days, but the group hopes that within the next decade it might be possible to harness these tiny predators in the fight against bacterial infections.
Bdellovibrio are one of few bacterial species known to prey on other bacteria, and can be found not only in the human body, but also in water and soil; anywhere in fact where there are other bacteria. Discovered in 1962, Bdellovibrio are around a sixth of the size of an average E coli, and find their prey by swimming with a
flagellum, or propeller. It is thought that they track down their prey by sensing chemical signals and lower oxygen levels in areas where there are other bacteria to attack.
They then collide with, attach to and burrow into their prey, sealing up the outer prey membrane behind them. 'Bdellovibrio can only live in bacteria with two cell membranes, called Gram-negative bacteria,' explains Dr Liz Sockett of the Institute of Genetics. 'Gram-negative bacteria are common and include E coli, Salmonella, Proteus, Serratia and Pseudomonas, which all cause infections in humans and animals.'
Once they are inside, Bdellovibrio settle between the two membranes and set about eating the prey from the inside, breaking them down into their basic components. These are then used as building blocks to make more Bdellovibrio cell parts, with the predator growing into a large Cumberland sausage-shaped cell in the process. 'The clever bit is that they're doing all of this sealed inside another bacterium so nothing else outside can eat what they're eating,' says Dr Sockett. When the Bdellovibrio have exhausted the prey contents, they split up to form several new predators, burst out of the empty shell of the prey and start all over again.
The Bdellovibrio lifecycle was described in 1962, but the genetics of the process has so far remained a mystery. 'It's all very well seeing this elegant process under the microscope, but if you're going to
understand what's happening you need to see which genes do what,' explains Dr Sockett. About five years ago the team started trying to do this by knocking out individual genes to see what happened. They genetically engineered Bdellovibrio with one gene missing and tested how efficiently the altered Bdellovibrio were at killing prey bacteria.
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