Scientists uncover bacterial cloaking

Scientists have uncovered the workings of a method bacteria responsible for diseases such as meningitis and blood disorders use to hide from the body's immune system.

An international research team led by scientists from the University of St Andrews has discovered how bacteria are able to cover their surface under a cloak of carbohydrate molecules to prevent being detected and targeted. Bacteria use a newly discovered protein that allows them to transport a cloak of carbohydrates from inside the bacterial cell that makes them invisible to the immune system.

The research, funded by the Biotechnology and Biological Sciences Research Council (BBSRC), raises the possibility that new drugs could be developed to disrupt the cloak and allow the immune system to attack the bacteria.

The bacteria's outer membrane is oil-based so it forms an effective barrier between the water-based interior and exterior of the cell. The research team has discovered that the bacterium safely transports the carbohydrates through the membrane using a previously unknown protein called Wza. The hollow inner part of the Wza protein creates a tunnel for the carbohydrates to pass through the cell membrane. While the protein is open to the cell's exterior, it is closed at the interior end and only opens to let the molecules through.

"Wza's shape and position in the cell membrane allows the bacterium to perform a very difficult trick", says Professor James Naismith of the Centre for Biomolecular Sciences at the University of St Andrews. "It acts much like an airlock. Wza allows the carbohydrate from inside the cell to cross the outer membrane without creating a hole that could cause the cell contents to leak out. It forms a 'protein tunnel' and plays a key role in allowing bacteria to invade the body under the radar of the immune system."

Moving forward drugs could be developed to block carbohydrates from passing through the membrane, or prevent the protein tunnel from closing again.

Professor Julia Goodfellow, BBSRC Chief Executive, said: "Research in basic biology underpins future healthcare and medical improvements. Only by investing in such research can we uncover the detailed workings of complex biological systems and generate the knowledge we need to make real progress in combating disease."