Developments in Science : Anti-Quorum Sensing Molecules

Anti-Quorum Sensing Molecules: The Future of Bacterial Resistance

The misuse of antibiotics has meant that some bacteria have become resistant, such as strains like the ‘superbug’ MRSA, and has caused for extensive research to be taken into other methods that will prevent harmful bacteria. Although new antibiotics have been created from different microbes, they are a finite source for antibiotics and so are only a short term solution. However, Bonnie Bassler, a microbiologist has discovered the crucial element in the on-going war with bacteria; the way in which bacteria co-ordinate collective behaviours and function as multi-cellular organisms through a mechanism known as quorum sensing.

Quorum Sensing

Quorum sensing is the bacterial communication phenomenon; during quorum sensing, bacteria produce, detect, and exchange signalling molecules known as auto inducers. The concentration of a particular auto inducer enables a population of bacteria to collectively regulate gene expression, thus meaning specific genes are only synthesized as particular population densities. This process is crucial to disease development because it ultimately controls the way that bacteria express virulence factors—the molecules that enable the bacteria to colonize a host. In bacteria, virulence factors are often encoded on mobile genetic elements, such as bacteriophages, and can easily be spread through horizontal gene transfer. Auto inducers bind to receptors in the bacteria, forming receptor:autoinducer complexes which bind to certain sites along the cell’s DNA, triggering the bacterium’s virulence genes.

Anti-Quorum Sensing

Anti-quorum sensing molecules would essentially prevent bacteria from communicating by strongly inhibiting quorum sensing through binding to the receptors in place of the autoinducers, thus upsetting the process. Said compounds would be specialised to target specific receptors of a bacteria type, and thus by being unable to carry out collective virulence activities that are critical for enabling bacteria to stay in the host, the immune system would have more time to get eliminate said pathogens.

Recently, researchers from Princeton University and the Howard Hughes Medical Institute developed a molecule to block quorum-sensing in the bacteria Chromobacterium violaceum which has a close homolog to a bacteria that causes particular trouble for cystic fibrosis patients. Due to the effectiveness of the mechanism of anti-quorum sensing, many scientists are now investigating other bacterial traits that could be similarly exploited.

The Benefits

Because anti-quorum-sensing molecules do not kill bacteria, only keep them from communicating, it is probable that bacteria would be less likely to develop resistance; nonetheless if a resistance does develop, it will be expected to progress far slower than resistance occurs in response to current antibiotics. Furthermore, ‘quorum-sensing antagonists represent potential lead molecules in the search for new antibacterial therapeutics’, and so coupled with the success in this particular field, it shouldn’t be too far in the future that this treatment becomes available for a wider audience.