Bacteria make a pact before they go on the attack. This communication happens by way of signal molecules. Each bacterium sends out little messengers to find out whether there are any fellow members of the species in the vicinity, and if so, how many. If the signal molecules encounter a larger number of like-minded organisms, this influences the bacteria’s behavior: They gang up and march off together. Microbiologists call this “quorum sensing,” because the bacteria work out whether they have a quorum, in other words the critical mass they need to stage a coordinated, successful offensive.
This has prompted microbiologists to look for ways of disrupting communication among bacteria. As Leo Eberl, professor at the UZH Institute of Plant Biology, explains, this way you can kill two birds with one stone: Blocking the virulence of the bacteria’s activity, and dissolving the biofilm in which the bacteria are entrenched.
This is a completely new tactic in the fight against bacterial infection. Until now, all attempts have revolved around using antibiotics to destroy bacteria on a large scale. Now microbiologists are taking a new tack. Instead of trying to kill the bacteria, they’re attempting to trick and neutralize them so that the human immune system remains intact rather than being weakened by a constant barrage of antibiotics. Despite this, Eberl admits that it probably makes most sense to compromise, trying the new approach while continuing the old one.
As is so often the case, nature has already provided the solution. Eberl says that the common garlic basically already uses both methods: neutralizing bacteria and killing them if necessary. What makes the smell and taste of garlic so special is its sulfur compounds, ajoene and allicin. And these are the weapons that can be used to beat bacteria. Ajoene is able to block the receptors in the bacterium that receive the messages from the signal molecules. If these receptors are blocked, the bacterium can’t sense the large number of fellow bacteria around it.
But to get a medically effective dose you’d have to eat ten whole heads of garlic. So Eberl and his team have begun extracting ajoene and allicin in their pure form and producing them synthetically. The first clinical tests with the artificial garlic have already taken place, with atomizers used to administer the substances directly into the lungs of patients with cystic fibrosis. Has it made them healthy? “It’s too early to answer that question,” says Eberl, “but things are pointing in the right direction.”