Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Salmonella bacteria sequenced

25.10.2001


Salmonella: two sequences are better than one
© SPL


Bugs behind typhoid and food poisoning give up genetic secrets.

Two teams have sequenced the genomes of two Salmonella bacteria. One is responsible for typhoid; the other causes food poisoning.

The genomes should lead to new ways to diagnose, treat and vaccinate against both diseases. Comparing the sequences should also clarify why the closely related bugs behave quite differently.



The two strains are called Typhi and Typhimurium. Typhi, the typhoid bug, infects only humans, attacking the liver, spleen and bone marrow. Gut-dwelling Typhimurium, a major cause of salmonella food poisoning, is much less fussy about where it sets up home. "It infects just about anything that walks or crawls on the face of the earth," says microbiologist Stanley Maloy of the University of Illinois at Urbana-Champaign.

Fatal flaw

Typhoid infects 16 million people each year and kills 600,000. Drug resistance is making matters worse. The Typhi team sequenced a strain from Vietnam that is resistant to several antibiotics.

The genome data should improve diagnostic tools, says team member Gordon Dougan of Imperial College, London. Typhoid is hard to diagnose because its symptoms resemble those of other diseases, including malaria and dengue fever, and the bug is difficult to recognize.

Typhoid vaccines are not fully reliable, and are not included in infant vaccination programmes. "We need another step in vaccine progress," says Dougan.

The rewards for such a step could be great. "If we could block its transmission in humans, we could eradicate it altogether - it’s got nowhere else to go," says Julian Parkhill of the Sanger Centre in Cambridge, UK, leader of the Typhi genome project. Relying on human hosts has painted Typhi into an evolutionary corner.

Typhi’s genome gives a strong hint about its narrow tastes. The bacterium has more than 200 ’pseudogenes’ - once-functional stretches of DNA that have been inactivated by mutation. Working versions of these genes were discarded during Typhi’s evolution for its current habitat.

The more flexible Typhimurium, which presumably requires a bigger biological toolkit, has about 40 pseudogenes. Each bug also has hundreds of genes that are not found in the other. "For two organisms that are classified as a single species, the amount of difference is quite a surprise," says Parkhill.

Problem and solution

Typhimurium has a less alarming public image, but is a bigger health problem than typhoid, says Michael McClelland of the Sidney Kimmel Cancer Center in San Diego, California, who led the project to sequence Typhimurium.

"It’s thought to be at least 30-fold underreported. There are probably hundreds of millions of cases every year in the world," says McClelland. He adds that gut-dwelling Salmonella may kill twice as many people - mostly infants and the elderly - as typhoid.

Typhimurium’s sequence reveals 50 previously unknown genes that code for proteins on its surface. These are potential vaccine or drug targets.

The bug is a tool as well as a menace. Weakened versions are used to deliver vaccines and cancer drugs. In mice, Typhimurium’s symptoms are very similar to human typhoid, making it a laboratory favourite for salmonella research.

The team behind the Typhimurium genome has designed microchips to identify the genes that the organism switches on in different situations. These might explain how the bug lives in different hosts, and why it has different effects on humans and mice.

"It’s a double-whammy - we can design therapies and study Salmonella’s evolution," says Typhimurium team member Sandra Clifton of Washington University in St Louis, Missouri.

There are more than 2,000 recognized strains of Salmonella enterica, with a wide variety of hosts and disease-causing capabilities. The genomes of several more strains are in the pipeline - comparisons between types "will provide the very best clues as to how [host switches] can happen in bacteria", says Maloy.

References
  1. Parkhill, J. et al. Complete genome sequence of a multiple drug resistant Salmonella enterica serovar Typhi CT18. Nature, 413, 848 - 852, (2001).

  2. McClelland, M. et al. The complete genome sequence of Salmonella enterica serovar Typhimurium LT2. Nature, 413, 852 - 856, (2001).


John Whitfield | Nature News Service
Further information:
http://www.nature.com/nsu/011025/011025-10.html
http://www.nature.com/nsu/

More articles from Life Sciences:

nachricht Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University

nachricht Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017
25.04.2017 | Laser Zentrum Hannover e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>