Meningitis Bacterium Code Cracked

Researchers in the UK and Germany have decoded all the genes of a bacterium that causes the most common form of meningitis.

Neisseria meningitidis infects half a million people each year, and is associated with major epidemics of meningitis in developing countries. The research paves the way for new methods of detecting, preventing and treating infections.

“This is the result of two years’ work by a team of 30. This research, funded by the Wellcome Trust, has already had – and will continue to have – a significant impact on our understanding of meningitis.”

Dr Julian Parkhill Head of the team at the Sanger Centre, Cambridge UK

The complete DNA sequence of type A N. meningitidis is published today in the science journal Nature by an international team based at the Sanger Centre, UK, the Max-Planck Institut für molekular Genetik, Berlin, Germany and The Wellcome Trust Centre for the Epidemiology of Infectious Disease at the University of Oxford.

One of the most interesting findings is a possible mechanism to explain how the bacteria change their surface coat and thereby evade detection by the body’s natural defences. Other features of the sequence may reveal how the bacteria transfer DNA between strains, thus changing disease-causing properties.

The sequence produced by the European team was released freely on the internet each week, and it has already been compared with the sequence of the related type B, which was sequenced by a team in the US. Comparison between the two sequences will help to identify why the bacteria differ, and which elements are responsible for infection and severity of the disease.

More information

1. The Sanger Centre, which receives the majority of its funding from the Wellcome Trust, is one of the world’s leading genome sequencing centres. Both the Sanger Centre and the Wellcome Trust have been at the forefront of efforts to keep sequence data in the public domain. https://www.sanger.ac.uk/ https://wellcome.org/what-we-do/our-work/research-centres-and-institutes

   The Wellcome Trust Centre for the Epidemiology of Infectious Disease https://wt-globalhealth.cam.ac.uk/programme-areas/infectious-diseases

   Max-Planck Institut für molekulare Genetik https://www.molgen.mpg.de/

2. The Wellcome Trust is the world’s largest medical research charity with an annual spend of some £600 million in the current financial year 1999/2000. The Wellcome Trust supports more than 3000 researchers at 300 locations in 30 different countries – laying the foundations for the healthcare advances of the 21st century and helping to maintain the UK’s reputation as one of the world’s leading scientific nations. As well as funding major initiatives in the public understanding of science, the Wellcome Trust is the country’s leading supporter of research into the history of medicine.

3. The DNA of every living organism is made up of four chemical ‘bases’ represented by the letters A, C, G, and T. The bases are paired together, A with T and C with G to produce double-stranded DNA in the familiar helix. The number of base-pairs varies from a few thousand for the smallest viruses to several billions for complex organisms. The DNA sequence of base-pairs contains all the instructions to make an organism: decoding that set of instructions is the heart of a sequencing project.

4. Meningococcal meningitis is caused by Neisseria meningitidis. Worldwide, N. meningitidis causes about 500,000 cases each year and is found only in humans. It is classified into five main groups (called serogroups). Different serogroups are prevalent in different areas of the world and the disease processes may differ. The serogroups can be divided into strains: many strains appear to be harmless. Serogroup A is the most widespread health threat and tends to occur in epidemics, principally in Africa. In 1996, 250,000 cases occurred in West Africa, resulting in 25,000 deaths. Transmission is by direct contact.

5. The genome of N. meningitides serotype A is 2,184,406 base-pairs in length, and could code for 2121 predicted genes. The most common repeated sequence is a ten base-pair element that occurs in nearly 2000 copies and forms the neisserial DNA uptake sequence, which helps to transfer DNA between cells. DNA transfer helps to contribute to genetic change.

6. A second significant family of repeated sequences are larger dispersed repeats that are associated with genes that code for cell-surface molecules. It is likely that the repeated sequences encourage rearrangements in these genes, leading to variation in the external properties of the cell.