- 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.
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- 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.
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- 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.
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- 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.
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- "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.
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- "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."
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- "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.
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- "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."
-
- * Bacteria reproduce by dividing. This can happen
every 15 minutes. In a day and a half, with sufficient food, one
microbe's progeny could outweigh the Earth.
-
- * Around 20bn E coli grow in the intestine of every
human being every day.
-
- * The total number of bacteria on Earth is estimated
to exceed 5m trillion trillion.
-
- * Certain species are able to withstand fierce
radiation, flourish in boiling water, survive at sub-zero
temperatures, multiply in acid or alkali, and eat concrete.
-
- * Bacteria have been found underneath polar ice, in
stratospheric clouds, and in rocks far below the ocean floor.
-
- * Antibiotic resistance is now a worldwide problem.
Strains of three life-threatening microbe are now resistant to more
than 100 antibiotics.
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- Guardian Unlimited © Guardian Newspapers Limited
2002
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- http://www.guardian.co.uk/Print/0,3858,4403319,00.html
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