- 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."
-
- * 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.
-
-
- 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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