Crime in the realm of bacteria

Christine Kaimer (left) and Susanne Thiery have investigated how soil bacteria fight each other.
Credit: RUB, Marquard

Who would have thought of bacteria: they can sneak up other microorganisms to kill and eat them up.

Bacteria have a variety of survival strategies to provide sufficient food in their densely populated habitats. Certain types of bacteria kill microorganisms of another type, decompose the cells and absorb them as nutrients. How this works is usually unknown. A research team on the biology of microorganisms around Dr. Christine Kaimer examined these processes in more detail. Together with colleagues from the USA, the researchers at the Ruhr University Bochum (RUB) report in the journal Cell Reports on 13. September 2022.

Stop at contact

So far, little is known about the relationship between robbers and prey in the realm of bacteria. However, researchers suspect that bacterial predators can greatly change the composition of a microbiome and thus influence the ecology of their habitat. To learn more about bacterial predator-prey relationships, Christine Kaimer's team examined the predator bacterium Myxococcus xanthus, that often occurs in the ground. It has recently become known that M. xanthus kills his prey cell in direct cell-cell contact: the predator approaches a prey cell, stops when a contact is made, and then causes cell death and decomposition within a few minutes. The researchers examined the molecular mechanisms of this process in more detail.

"We have M. xanthus genetically modified and then tracked the interaction of predator and prey cells under the microscope in real time,” reports Christine Kaimer. “This enabled us to show that two highly specialized protein section systems work together during the killing process, i.e. protein complexes that presumably transport certain proteins from the predator cell into the prey cell. "A so-called Tad-like system initially only causes the prey to be cell-death. A type III-like system is required for the decomposition of the prey cell so that the nutrients can then be absorbed.

Killing is initiated precisely

Images with fluorescence-labeled proteins showed that the protein section systems in the M. xanthus-Collect the cell exactly on the contact surface between the predator and the prey. Apparently feels M. xanthus contact with a prey cell and can initiate the killing process very precisely. "We do not yet know exactly how the protein section systems react to contact with prey and which potentially toxic proteins they release," says Christine Kaimer. “In any case, bacterial predation behavior is a fascinating field of research for us, where there is still a lot to learn about the coexistence of bacteria in their natural environment."

The work was funded by the German Research Foundation Ka 3361 / 3-1.

Source/Credit: Ruhr University Bochum

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