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University of Basel

09 November 2020

Yin and Yang: Two signaling molecules control growth and behavior in bacteria

Caulobacter bacteria in sessile and mobile lifestyle, forming the yin & yang symbol
Yin and Yang: two competing signaling molecules control Caulobacter lifestyle. Pink: Swarmer cell with high ppGpp level; blue: sessile form with high c-di-GMP level. (Illustration: University of Basel, Biozentrum)

Bacteria are considered to be true experts in survival. Their rapid adaptive response to changing environmental conditions is based, among other things, on two competing signaling molecules. As the “Yin and Yang” of metabolic control they decide on the lifestyle of bacteria, as reported by researchers from the University of Basel. The new findings also play a role in the context of bacterial infections.

Whether they are pathogens, deep-sea microbes or soil-dwelling organisms, in order to survive, microorganisms must be able to adapt rapidly to diverse changes in their environment, including nutrient depletion. Bacteria owe their extraordinary ability to quickly adjust to adverse living conditions to small signaling molecules.

Scientists headed by Professor Urs Jenal and Professor Tilman Schirmer from the Biozentrum, University of Basel, have now discovered that bacteria use two chemically related signaling molecules to adapt their lifestyle to the prevailing living conditions. The researchers present their results in the latest issue of “Nature Microbiology”. Like Yin and Yang, the two molecules embody two forces that control bacterial growth and metabolism reciprocally.

Bacterium with two different lifestyles

The researchers investigated the antagonistic nature of the two signaling molecules ppGpp and c-di-GMP in the cell using Caulobacter crescentus as a model organism. This bacterium can slip into two different roles: It can be found in a free-swimming form that is unable divide and in a surface-attached, reproductive state.

Both the lifestyle and the environmental conditions are reflected in the concentration of the two signaling molecules. This information is detected by a protein that binds both signaling molecules and acts a molecular switch, controlling growth, metabolism and lifestyle of the bacterium.  

Signaling molecules determine bacterial way of life

The signaling molecules ppGpp und c-di-GMP compete for binding to the master switch. “In swarming bacteria with high levels of ppGpp, the protein is switched on; it is active,” explains Urs Jenal. “In this state, glucose consumption is in full swing. Simultaneously, the resulting harmful oxygen radicals are efficiently neutralized.” This ensures, that metabolic reactions adapt to the high energy demand of the motile swimmer cells and cell damage is averted.

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