Bacterial conversation stopper

Molecules that interrupt the chemical conversations of bacterial communities are showing early promise in beating the bugs. 

Helen Blackwell at the University of Wisconsin-Madison, US, has developed compounds that can target specific bacteria to prevent them from cooperating with each another, leaving them more vulnerable to antibiotics. 

Bacteria in a growing colony use simple organic molecules to communicate with each other. This allows them to regulate the size of the community, and collectively form a polysaccharide coating, which can prevent antibiotics from reaching the bugs. 

'We wanted to design some compounds to interrupt these conversations,' said Blackwell. Stopping the bacteria communicating doesn't reduce their numbers, but does prevent them teaming up. The strategy is relatively new: 'there are only about five labs worldwide who are working in this area,' said Blackwell. In her latest research, she has proved that the conversation-stopping compounds can be tailored to silence specific species of bugs living in mixed communities - rather like interrupting only English-speakers at a multilingual UN meeting. 

Her team has produced a series of N-acylated  L -homoserine lactones, key signalling molecules used by Gram-negative bacteria. At least two compounds are good at blocking biofilm formation in Pseudomonas aeruginosa, a widespread and otherwise harmless bacterium that causes disease in immunocompromised patients. 

Adding a halogen atom to an aromatic ring in the compound was enough to make the compounds highly specific - and switching the halogen atom's position in the ring can retarget its activity to a different strain of bacterium. 'We didn't believe such a tiny change could have that effect, but it does,' said Blackwell. 

Mark Peplow