Study finds how bacteria detect and ingest new DNA

A new study by researchers at Imperial College London has identified how Neisseria meningitidis, a type of bacteria that causes life-threatening meningitis and septicaemia, is able to detect and ingest new DNA and generate different strains.

A piliated Neisseria meningitidis bacterium as seen by immunofluorescence microscopy. The bacterium is in red, the pili are in green.

One way in which bacteria overcome our immune defences is by generating new variants that either go undetected, or are more resistant to antibiotics and can cause serious disease outbreaks. This usually occurs through a process known as natural transformation where bacteria ingest free DNA that is abundant in many environments and acquire new genetic traits.

Natural transformation has been studied for decades, and has been instrumental to one of the most important discoveries in biology: that DNA is the material that carries genetic information. However, it remains unknown how bacteria are able to detect the new DNA they ingest.

Published today in Proceedings of the National Academy of Sciences, a study by Dr Vladimir Pelicic and professor Stephen Matthews from the MRC Centre for Molecular Bacteriology and Infection has identified a 'molecular sensor' for DNA in Neisseria meningitidis.

Hair-like structures called pili found on many bacteria have long been known to be involved in natural transformation. In this study, the researchers discovered that a protein component of pili is capable of sensing DNA outside the cell, binding it very strongly using a previously unrecognised mechanism.

The bound DNA is then thought to be imported in the bacteria by retracting the pili, which act like grappling hooks.

"Similar pili and proteins are found in hundreds of bacterial species, several of which cause disease in humans," said Dr Pelicic "The challenge now isto understand in greater detail the biology of these fascinating molecular machines, and - potentially - to exploit these findings to develop new drugs targeting them that would be effective against a very broad spectrum of bacteria."

This research project was funded with grants from the Wellcome Trust and the Biotechnology and Biological Sciences Research Council.