Infection Biology of Salmonella

During hot summer months, Salmonella frequently dominates the headlines with reports of infections caused by contaminated ice cream or egg dishes. The aggressive and quick bacteria rapidly infect a large number of people. However, our understanding of the mechanisms that Salmonella uses to infect us is fragmentary at best. In HZI’s Department of Molecular Infection Biology, the junior research group Infection Biology of Salmonella is studying the bacterium’s attack tactics – in order to use this information to develop new strategies in the ongoing fight against enteropathogenic bacteria.


Our research

Infection cycle of salmonella

Raw eggs, poultry, and ice cream can be contaminated with Salmonella. Infections with Salmonella are therefore a global economic and health problem.. In 2010, 50,000 cases of salmonellosis were reported in Germany alone. The pathogen causes gastroenteritis (food poisoning) and can quickly become life-threatening especially in small children and elderly individuals.

The strategy Salmonella uses to infect us is very sophisticated. The first step involves the bacterium using long appendages (its flagella) to move towards the host cell. The flagella rotate and drive the bacterium like a ship’s propeller.

Type III-secretion system to inject the salmonella into host cells

In the next step Salmonella infects its host cells using a type III secretion system, a molecular syringe. The bacterium docks to the cell and injects signaling molecules (so-called effector proteins) via its type III secretion system that promote entry of Salmonella bacteria into the host cell. The combination of efficient motility and injection of effector proteins makes Salmonella such a successful pathogen.

However, to date, little is known about the molecular relationship between these two systems – which are used not only by Salmonella but by other pathogenic bacteria as well. Our scientists utilize methods ranging from bacterial genetics to microscopy, from biochemistry to infection biology to help them examine these relationships and find out more about the different events that lead to a bacterial infection.

Some of the questions our researchers are asking include:

Molecular structure of the type III-secretion system at a cell membrane
  • Can Salmonella detect a potential host cell using chemical signaling – and then swim directly towards it?
  • What happens to the flagellum once the bacterium has entered into the host cell?
  • How does Salmonella manage to ultimately escape from the host cell?
  • How does the type III secretion apparatus work – and what is the nature of its signal?
  • By what mechanism are the effector proteins transported into the host cell?

The ultimate goal behind all of these questions is to identify potential targets for new antibiotics. And, in light of increasing antibiotic resistance, they are urgently needed.


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Audio Podcast

  • Gefährliche Spritzen – Salmonellen infizieren uns mit molekularen NadelnSalmonellen leben und töten überall auf der Welt. Mehrere Hundert Millionen Kranke gehen jährlich weltweit auf ihr Konto.Die Strategien mit denen sie sich unseren Behandlungsversuchen entziehen, werden immer raffinierter, die Resistenzen gegen Antibiotika immer mehr. Marc Erhardt geht auf der Suche nach neuen Therapieansätzen einen ungewöhnlichen Weg: Er untersucht das Spritzbesteck, mit dem Salmonellen uns infizieren und er sucht nach Ansätzen, die die Bakterien nicht töten – und damit Resistenzen provozieren –, sondern nur ihre Spritze verstopfen. Begleiten Sie Marc Erhardt in sein Labor…
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