Bacteria 'send message' to ailing colonies
Tim Radford, The Guardian, 04/29/2002
British scientists have caught bacteria in the act of passing information to each other - even when separated by a plastic wall. The discovery could throw new light on the spread of antibiotic resistance in hospitals.
Mathematical physicist Alan Parsons and biologist Richard Heal, work for QinetiQ - formerly the Ministry of Defence science laboratory - at Winfrith in Dorset. They report in the Journal of Applied Microbiology that they grew separated colonies of bacteria, one in an ordinary nutrient, one in a dish of food that had been spiked with antibiotic.
At first, the medicinally-treated bacteria began to die. If they were totally sealed off from the healthy bacteria next door, they would all die. But if there was a small gap through which air could pass between the two colonies, the ailing bacteria would recover.
The only conclusion could be that the healthy, stable bacteria next door were sending their stricken cousins some kind of survival advice - in the form of information about antibiotic resistance.
"If these unstressed bacteria are present then we find that the bacteria that are attacked by the antibiotic actually do not die. A large proportion of them survive and they begin to recover," Professor Parsons said.
"It happens in a few hours. We first discovered this a year ago and have done a great many controlled tests to throw out other possibilities."
"We have only tried it on two bacteria that happened to be available. It worked with both. But there are obviously thousands of other strains and species we haven't tried.
"We don't know if this thing exists between the pathogenic bacteria that hospitals are interested in. This is something we would like to find out. It would be surprising if they did not have some similar capacity."
The means by which bacteria pass messages to each other is so far unknown. The guess is that signals could be carried by airborne molecules released by microbes.
Prof Parsons and Dr Heal speculated that bacteria were sending electromagnetic signals to each other, but ruled out this possibility after they found that the effect only occurred when the two colonies were linked by a passage of air.
Winfrith is a centre for research into naval sonar and underwater acoustics. The two scientists had been experimenting with bacteria as "living sensors" which could register acoustic pressure. The discovery that the microbes could signal to each other through the air was completely unexpected.
If confirmed in experiments with the kind of infectious bacteria that spread pneumonia or blood poisoning, or other life threatening illnesses, the discovery could have profound consequences.
But there was a twist. The two scientists found the same result when they used three kinds of antibiotics - but not with a fourth variety, from a different class.
"So clearly, some antibiotics are effective against the signal, and some not," said Prof Parsons.
"It is absolutely fascinating and astonishing. I don't have a picture of it yet. We don't know what the signal is, we don't know how it activates the resistance mechanism in the stressed bacteria. That has to be sorted out. We are very keen to pursue this further."
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