Martin Luther University Halle-Wittenberg

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Chemical Communication

Organisms are in constant exchange with their surroundings. Chemical compounds play an important role in this aspect and serve as communication molecules between the different organisms (e.g. plants, insects and other animals, or microorganisms). We are interested in the chemical nature of these compounds and their biological activities.

Quorum-Sensing molecules from cyanobacteria

Quorum sensing refers to the capacity of bacteria to monitor their population density and regulate gene expression accordingly. This allows bacteria to adopt social behaviour in order to gain benefits over competitors, conquer new niches or sustain survival of the population. The inhibition of quorum sensing (QS) systems in pathogenic bacteria has been discussed as a new promising strategy for anti-virulence therapy, since many pathogenic bacteria use QS to regulate the expression of virulence factors or the formation of biofilms.

Although cyanobacteria have gained much attention as a prolific source for novel bioactive compounds, little is known about QS between cyanobacteria or about cyanobacterial natural products interfering with the QS of other bacteria. This motivated us to search for QS interfering metabolites from cyanobacteria as well as to study their bioactivity in more detail (e.g. identifying their targets in the QS systems of other bacteria). We are not only aiming at a better understanding of chemical communication between bacteria, but also hope to be able to identify compounds that can serve as lead structures for the development of anti-virulence drugs.

Tomasz Chilczuk is working on this project, which was funded by the DFG (GRK 1708) before we moved to the University of Halle-Wittenberg.

Interactions of cyanobacteria with plants

Hormogonia are motile filaments of cyanobacteria of the orders Nostocales and Stigonematales. As they are the "motile forms" of the respective strains, they are e.g. formed when the cyanobacteria experience environmental stress, and enable the cyanobacteria to spatially evade these stresses. Hormogonia are also crucial for the formation of plant-cyanobacteria symbioses, in which cyanobacteria serve as nitrogen fixing symbionts. Host plants secret a hormogonium indicing factor (HIF) into the rhizosphere to convert cyanobacteria in the root environment to hormogonia, which are then attracted to move into the roots of the plants. Once the attracted cyanobacteria have reached the roots, however, plants use hormogonia repressing factors (HRF) to have the cyanobacteria differentiate back to their non-motile form, so they are forced to settle in the roots, and commence nitrogen fixation for the plant. Despite the fact that this ecological process has high importance for global nitrogen fixation and ecosystem development, nothing is known about the chemical nature of the factors and the mechanisms of their reception by the cyanobacteria cells.

Steffen Breinlinger is working on this project.