Pseudomonas uses a modular design for rapid adaptation

HZI researchers show how Pseudomonas aeruginosa adapts to environmental conditions

Modularer Aufbau des Genoms von Pseudomonas aeruginosa: Globale Transkriptionsfaktoren kombinieren verschiedene Sigmafaktoren zu funktionellen Gruppen.© HZI/EckweilerBacteria are exposed to constantly changing environmental conditions to which they need to adapt in order to survive. They manage to do this by activating the production of certain genes. Scientists of the Helmholtz Centre for Infection Research (HZI) in Braunschweig recently showed that bacteria adapt more rapidly and more sustainably if they utilise pre-existing modules in the genome rather than searching through the entire genome for solutions. The researcher's results are published in "Scientific Reports". 

The Pseudomonas aeruginosa bacterium is a much-feared cause of hospital-acquired infections, which can have a severe and often even fatal outcome. The pathogen is a skilled survivor. Whether in the water or on the ground, it adapts extremely quickly to new environmental conditions, and can survive even under extreme conditions. "We elucidated an important mechanism that allows this adaptation to take place so rapidly and successfully," says Dr Denitsa Eckweiler, who is a scientist with the Molecular Bacteriology department of the HZI directed by Prof Dr Susanne Häussler. 

To be able to rapidly and properly adapt to new environmental conditions, the pathogen relies on the optimisation of individual modules of the genome, so-called sigma factors. These proteins play a crucial role in the implementation of genetic information since they facilitate the transcription of DNA into readable RNA. Depending on the predominating environmental conditions, the bacteria produce different sigma factors that are specific for different genes. "The sigma factors categorise the genes into groups and order them," says Dr Sebastian Binder, who is a scientist with the Systems Immunology department of the HZI directed by Prof Dr Michael Meyer-Hermann. So-called transcription factors then decide which genes are ultimately read and activated. 

"We were able to show that transcription factors use this sorting process to find genes and to adapt to changing environmental conditions," says Eckweiler. "This means they do not randomly select the genes to be activated from the entire genome, but rather optimise specific modules from the pre-sorted toolbox." This has two advantages. "Our model shows that evolution does not only proceed more rapidly by this means, but also is more successful," says Binder. "It appears to be easier to optimise a certain module than to attempt to improve the entire genome." 

The principle also explains why the bacterium is able to adapt to changing conditions so quickly. "This allowed us to take an important step in the fight against this bacterium. Once we know the mechanism accurately enough to be able to disturb it, we might find new approaches for therapy," says Eckweiler. 

Original publication:
Sebastian C. Binder, Denitsa Eckweiler, Sebastian Schulz, Agata Bielecka, Tanja Nicolai, Raimo Franke, Susanne Häussler & Michael Meyer-Hermann. Functional modules of sigma factor regulons guarantee adaptability and evolvability. 2016 Feb 26. DOI: 10.1038/srep22212.

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