Signaling receptor may provide a target for reducing virulence without antibiotics

Nov 21, 2012
Microbiology: Eavesdropping on bacterial conversations
Many types of bacteria cells can communicate using quorum sensing. Credit: iStockphoto/Thinkstock

For decades, microbiologists thought that bacteria act individually, unaware of their multitudinous counterparts involved in causing the same infection. In the past two decades, however, they have discovered that many species of bacteria 'communicate'. In fact, bacteria can signal to each other that their numbers are sufficient to launch a coordinated attack.

Owing to the relative newness of this research area, few of these cell-to-cell signaling systems, known as quorum sensing, have been described. Now, by working with Burkholderia cenocepacia, an opportunistic pathogen that infects , a research team led by Lian-Hui Zhang from the A*STAR Institute of (IMCB) has described a previously unknown quorum-sensing system that is present in many human bacterial pathogens.

Many types of individual bacterial cells send and receive 'messages' via called quorum-sensing (QS) molecules. When concentrations of QS molecules reach a threshold, individual simultaneously activate their . By identifying the signaling molecules and decoding these communications, researchers may also be able to reduce bacterial virulence by interrupting these conversations. Such treatments could provide an alternative to antibiotics.

For the QS molecule of B. cenocepacia, BDSF, Zhang and his co-workers identified a novel receptor, RpfR. The researchers produced mutant bacteria that lacked either the receptor RpfR, or the capacity to produce the signal BDSF. Both types of showed decreased motility, produced fewer host-degrading enzymes, and were less able to form biofilms—bacterial aggregates encased in slime—indicating that BDSF and RpfR act together to send and receive the virulence signal.

Zhang and his co-workers also showed that, unlike other QS receptors, RpfR is a multitasking molecule. In other systems, after the receptor binds the QS molecule, it recruits another molecule to perform the next step in the signaling cascade and trigger gene expression. In the quorum-sensing system of B. cenocepacia, however, RpfR binds BDSF, then changes shape and performs the next step itself. Combining the two functions in a single molecule expedites the signaling process, and enables bacteria to adapt very quickly to changing environmental conditions.

The team's search of known bacterial genomes showed that the system is present in many other pathogenic bacteria, including several groups that produce opportunistic infections in immune-compromised patients. "We would like to design chemical compounds to block the BDSF receptor, to compete with BDSF signals and reduce the virulence and pathogenicity of B. cenocepacia," says IMCB team member Yinyue Deng.

Explore further: Environmental pollutants make worms susceptible to cold

More information: Deng, Y., Schmid, N., Wang, C., Wang, J.,  Pessi, G. et al. Cis-2-dodecenoic acid receptor RpfR links quorum-sensing signal perception with regulation of virulence through cyclic dimeric guanosine monophosphate turnover. Proceedings of the National Academy of Sciences USA 109, 15479–15484  (2012). www.pnas.org/content/109/38/15479.abstract

add to favorites email to friend print save as pdf

Related Stories

Fighting bacteria's strength in numbers

May 17, 2012

Scientists at The University of Nottingham have opened the way for more accurate research into new ways to fight dangerous bacterial infections by proving a long-held theory about how bacteria communicate ...

Marine bacteria cope with harsh mileu, learn to adapt

Sep 07, 2010

Marine bacteria live in a harsh mileu. They must constantly cope and adapt to changes in salinity, pH, temperature and other parameters. In her thesis, Barbara Weber, Umea University, studied how bacteria communicate with ...

Recommended for you

Environmental pollutants make worms susceptible to cold

Sep 19, 2014

Some pollutants are more harmful in a cold climate than in a hot, because they affect the temperature sensitivity of certain organisms. Now researchers from Danish universities have demonstrated how this ...

A new quality control pathway in the cell

Sep 18, 2014

Proteins are important building blocks in our cells and each cell contains millions of different protein molecules. They are involved in everything from structural to regulatory aspects in the cell. Proteins are constructed ...

User comments : 0