Single Review on past events

Why should we try to understand microbes? – By asking this question Thomas Böttcher started his presentation “From Signals to Language: Insights into Bacterial Population Behavior” and made clear the importance of his research. While the human body contains about 10 trillion human cells, ten times more, 100 trillion microbial cells live in and on us. Of these 100 trillion microbial cells many are beneficial to us and even determine who we are, but many can cause diseases. Worldwide approximately 17 million deaths per year are caused by infectious diseases, mainly bacteria.

Hence the chemist´s aim is to understand microbial behavior and find alternatives to antibiotics. Concretely he wants to investigate the signals involved in the control of bacterial population behavior, discover small molecules to manipulate bacterial behavior, and finally develop novel drugs to treat bacterial infections.

Understanding microbial behavior means understanding microbial communication. Microbes communicate in order to achieve coordinated population behavior. In larger collectives the behavior of bacteria is controlled by a process known as quorum sensing that uses self-produced signaling molecules as a measure for the number bacteria in a given volume. The presence of a sufficiently high population density of bacteria in a particular environment leads to a rapid increase in the concentration of these signaling molecules. When the concentration exceeds a certain threshold, a molecular switch is flicked, which results in the expression of certain genes, e.g. enzymes required for the formation or degradation of biofilms. Biofilms are, besides swarming, one extreme of bacterial population behavior which cause 90 % of the human diseases. Biofilms are a physical barrier and give the bacteria increased resistance to antibiotics.

Such signaling molecules can also be produced by one organism in order to manipulate the behavior of another. Thomas Böttcher could find out that the bacterium Shewanella algae produces a previously unreported molecule that inhibits the bacterium Vibrio alginolyticus from swarming in its vicinity. This molecule is a siderophore, an iron-binding compound used by bacteria for taking up iron from their environment. Biologically available iron is usually relatively limited and in great demand. Such siderophores can often be used not only by the bacteria that produce them, but also by other strains. However, the molecule called avaroferrin binds iron in a way that prevents bacteria other than the producer from using it. Avaroferrin therefore prevents Vibrio alginolyticus from pirating iron and secures this essential resource for its producer. Foreign organisms are thus cut off from the iron source and are unable to grow effectively. Accordingly avaroferrin has great potential as a biotechnological tool, for example for the treatment of bacterial infections.