麻豆淫院

Biofilms are conglomerates of bacteria and other organisms, which are feared in medicine as well as other areas because they can contain pathogens and are highly resistant to treatment. Chemists at Heinrich Heine University D眉sseldorf (HHU) have, in collaboration with colleagues from Munich and Groningen, examined how the polysaccharide "Pel"鈥攁 central component of many biofilms鈥攊s exported out of the cell by the pathogen P. aeruginosa.

In an article in Nature Communications, they describe the structure of the so-called PelBC export complex, which represents the last station in the cell before "Pel" is released.

Bacterial biofilms are common aggregates of cells, which ensure the survival of microorganisms in harsh environments and are highly resistant to mechanical and chemical treatments. They can present a danger to humans when they cover the surfaces of medical devices or support the colonization of harmful organisms in the food industry.

Biofilms enable bacteria to exchange genomic information with each other. This makes it easier for them to develop resistance to antibiotics鈥攚hen resistant bacteria pass on resistance information to other species. They also facilitate nutrient uptake.

Where pathogenic bacteria form biofilms, it is important to understand which mechanisms play a role in their formation. The HHU research group "Synthetic Membrane Systems" headed by Professor Dr. Alexej Kedrov has collaborated with colleagues from Ludwig Maximilian University (LMU) in Munich and the University of Groningen in the Netherlands to study this. They have focused on the pathogen Pseudomonas aeruginosa (for short: P. aeruginosa), which can cause pneumonia, urinary tract infections and meningitis in humans. The pathogen is resistant to multiple antibiotics and is a key so-called "hospital germ."

Professor Kedrov states, "In order to form biofilms, the bacteria synthesize and export various biopolymers, above all polysaccharides鈥攕pecific sugar chains. Despite decades of research, knowledge of how the synthesis or transport takes place remains limited. We have concentrated on the polysaccharide 'Pel,' which is produced by P. aeruginosa."

The production of Pel requires a protein machinery comprising several sub-units, which crosses two membranes. "To date, however, neither the structure of the machinery nor its dynamics were known. With the help of cryo-electron microscopy, we can resolve the structure of the PelBC complex in the lipid membranes and identify the path of the Pel polysaccharide," says Kedrov.

Marius Benedens, the lead author, adds, "Our study shows how electrostatic interactions are used in nature to assemble the export complex and enable the transport of the polysaccharide. However, for the cell to survive, the pore cannot remain permanently open for transport. A small conformational change at the end of this pore is therefore necessary鈥攁 tiny gate is opened, so to speak."

"It is fascinating to see the organization of a complex structure in such detail. Among other things, it shows how nature solves challenges in protein design, for example, the coupling of a symmetrical ring of PelC sub-units to the asymmetrical PelB channel. It may be possible to use our results to block the export of Pel in a targeted manner and thus suppress biofilm formation," says Kedrov.

In the next step, the research group intends to examine this export process in detail. Another involved protein complex, which is responsible for the synthesis of Pel in the cytoplasm of the cell and its transport across the inner membrane, will also be examined in greater detail.