LORNE PROTEIN: The lingua franca of bacteria

The Lorne series of conferences -- Protein, Cancer and Genome -- begin in early February. Over the coming days, we'll preview the events with profiles of some of their key speakers and issues.

One of the major international speakers at the Lorne Protein Conference will be Princeton University microbial geneticist, Prof Bonnie Bassler, discoverer of 'quorum sensing' in bacteria.

Bassler has shown that bacteria secrete and sense species-specific signalling molecules that tell individual cells whether they are in the company of conspecifics. The concentration of signalling molecules in the environment conveys information about the number of cells in the population.

Bassler says that a single bacterial cell entering its host's body "gets creamed by the immune system", but if it waits until it is in company, it can successfully infect its host. Quorum sensing also switches bacteria into a virulent state in which they may secrete toxins or virulence factors, or form complex communities that produce biofilms on surfaces.

Bassler is best known for discovering that, in addition to their species-specific 'dialects', bacteria also employ a lingua franca -- in the form of an ancient signalling molecule that is secreted and 'understood' by all species -- even across the evolutionary gulf between gram-positive and gram-negative species.

Uniquely, in Bassler's model, the luminescent marine bacterium Vibrio harveyi, it comprises two sugar-like ring molecules linked by a single boron atom. Furanosyl borate ester is the only biologically active molecule known to incorporate boron.

Bassler and her colleagues have recently made another remarkable discovery: although the basic structure of the molecule is universal, distantly related species secrete their own distinctive variants of the lingua franca molecular signal.

Yet, somehow, the signal is universally 'understood' by all bacteria. A microbe receiving a signal from a different species somehow translates it into its own native 'language' -- a biochemical analogue of the Babel Fish universal translator in The Hitchhiker's Guide to the Galaxy.

Bassler says it is an outstanding target for new drugs that, by mimicking the signalling molecule, would prevent infection by disrupting bacterial communication. Princeton chemists have already synthesised analogues that block quorum sensing in V. harveyi, quenching its colonial glow.