This month, Journal of Applied Microbiology publishes a ground-breaking study demonstrating that bacteria which are physically separated can transmit information through the air. It is well documented that bacteria can exchange messages by releasing substances into a surrounding liquid culture medium, but this new study is the first to demonstrate signalling between physically separated bacterial cells.
Professor Alan Parsons and Dr Richard Heal of QinetiQ ltd, have shown that physically separated colonies of bacteria can transmit signals conferring resistance to commonly used antibiotics. The discovery is thought to have direct application against the growing problem of the resistance of bacteria to antibiotics – in particular in preventing the growth of biofilms, which often cause infection associated with surgical implants.
Professor Parsons and Dr Heal conducted their experiments using a Petri dish divided into two compartments, connected by a five-millimetre air gap between the top of the wall and the lid. In one compartment they placed drops of the bacterium Escherichia coli, together with the antibiotics. When the other compartment was empty, the bacteria were killed. However, if thriving colonies of E.coli were placed in the other compartment, the first colony of bacteria not only survived, but also multiplied. Yet, if the gap between the compartments was sealed, the bacteria in the first compartment died. Professor Parsons and Dr Heal concluded that the bacteria must have been responding to some kind of airborne signal from the adjacent culture probably in the form of a volatile chemical.
Further research is still required to identify the exact nature of the signalling mechanism, and to establish whether blocking of the signalling mechanism might prove a valuable weapon in combatting the problem of bacterial antibiotic resistance.
Blackwell Publishing Ltd. May 2002.