Microbial Communication

If when you wake up in the morning your teeth feel sticky, this indicates bacteria that live in your mouth have formed a slimy structure called a biofilm. To do this, they engage in a very special form of communication using chemical signals. Furthermore, bacteria in the ocean communicate with one another as well as with the tiny planktonic algae which provide about half of the world´s primary production to the global carbon cycle. Our scientists are deciphering these processes in order to be able to influence them, for instance to prevent caries.

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Bacteria communicate with one another but, since they have neither mouth nor ears, they use chemical signals instead of sounds. They release small molecules into their environment and respond to the molecules of other bacteria. Such molecules are known as “auto-inducers”. 

Researcher examine the mechanism of the quorum sending at Streptococcus mutans. © HZI

Based on their structure and concentration in the immediate environment, the bacteria are able to determine how many other bacteria are in the neighbourhood. This type of chemical communication is called “quorum sensing”. Auto-inducers typically regulate characteristic bacterial properties, which are much more effective when they are performed by a large number of cells, such as luminescence, the production of antibiotics, the formation of biofilms, or the production of toxins.

Scientists in the group “Microbial Communication” investigate the mechanisms of quorum sensing in Streptococcus mutans, a human pathogen that causes caries, and in Dinoroseobacter shibae, a representative of the Roseobacter Group. They study the functions of genes and proteins using molecular methods that include gene knock-outs, micro-arrays, mRNA sequencing, and heterologous expression of proteins. They have developed new test systems for finding inhibitors of quorum sensing.

A very interesting source of such inhibitors is the Myxobacteria, a group of soil bacteria that form fruiting bodies, which produce a large diversity of novel chemical structures with unknown biological functions. These quorum sensing inhibitors may eventually be used as novel anti-infectives. Such drugs are not required to kill the pathogen; rather they are intended to weaken its capability to make us sick.

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