Staphylococcus aureus can develop resistance
(Picture: Pfizer)
(Picture: Pfizer)
The growing problem of resistance to some antibiotics has been linked to more illness and death from infectious diseases.
It is known that bacteria exchange messages by releasing substances into the fluid in which they are growing, but new research suggests they can send signals through the air.
It is the first time airborne communication has been identified, say the team who carried out the study.
The findings of Richard Heal and Alan Parsons of QinetiQ, formerly part of the UK Government's Defence Evaluation and Research Agency, are reported in New Scientist magazine.
Heal and Parsons did their experiments in a Petri dish divided into two compartments.
The only connection between them was a five-millimetre air gap between the top of the wall and the lid.
In one compartment they placed 100 or so blobs of the bacterium E.coli, together with various antibiotics.
When the other compartment was empty, the bugs simply died, killed by the antibiotics.
Thriving bugs
However, if thriving colonies of E.coli were placed in the other compartment, the first lot of bugs not only survived, but began to multiply.
If the gap between the compartments was sealed, the bacteria in the first compartment died.
So the bugs in the second compartment must have sent some kind of airborne "survival" signs, Heal and Parsons conclude.
The warning signal made the recipient bacteria turn on genes that make them resistant to at least three common antibiotics - ampicillin, tetracycline and rifampicin.
However, the researchers have not yet identified the signal. Mr Heal doubts whether it could be any of the known chemical messengers or pheromones that bacteria use.
Nor is it likely to be any of the volatile substances discharged into the air by some soil microbes.
Blocking resistance
Mr Heal said: "We've tried without success to isolate the chemical signal from the air by dissolving it. Next we'll try gas chromatography."
They hope that by identifying and neutralising the signal, it might be possible to stop new colonies of bacteria growing or stop them developing resistance to antibiotics.
Mr Heal says he expects the discovery to be of most use preventing the growth of biofilms, which often clog surgical prostheses and catheters.
Microbiologist Professor Peter Hawkey, from the University of Birmingham, is intrigued by the findings.
He said: "What I find unusual is that the signalling substance is potentially airborne. The levels of resistance being switched on by this substance are quite low.
"However it does help to stimulate research into fundamental control mechanisms of antibiotic resistance in clinically important bacteria, to understand how bacteria are spread and how bacteria can be switched on to resistance."
Dr Douglas Kell, who studies bacterial pheromones at the University of Wales in Aberystwyth, said the results were "striking".
He said he knew of no other reports of airborne signalling between bacteria, but said there were parallels in plants.
Leaves wounded by biting insects send out a gas called methyl jasmonate that warns other leaves to prepare for attack.