How a certain bacterium communicates and makes us sick

Assistant Professor Xin Yong and graduate student Ao Li from the Department of Mechanical Engineering, along with Associate Professor Jeffrey W. Schertzer of the Department of Biological Sciences, published their findings in the Journal of biological chemistry.

The study examined how bacteria communicate via the transport of small molecules. Yong and Schertzer explained that communication molecules stimulate the production of vesicles in the outer membrane. These small packages come off the surface of the bacteria and contain highly concentrated toxins.

Originally, it was assumed that the communication molecule induced vesicle production by controlling the expression of genes, but this is not what happens.

Yong and Schertzer decided to work together on a model to better understand how the communication molecule inserts into the membrane of bacteria in order to physically stimulate the production of these toxin vectors.

"It's hard to see the molecular details at this level," said Schertzer. "But with Dr. Yong's expertise, we were able to build a computer model that helped us understand what's really going on between the individual molecules."

Yong's model allowed them to examine the details of the molecule and better understand how it interacted with the membrane over a very short period of time.

"Our most important discovery is that the communication molecule must penetrate the membrane in a very specific way," said Schertzer. "It bends like a book, then expands once it gets into the membrane."

Schertzer and Yong explained that the communication molecule had both a head and a tail known to be flexible, but they did not expect this type of change. In the future, they hope to test what would change in the interaction when the tail is removed or the head is changed.

Although the study may appear quite specific, it has broader implications for all Gram-negative bacteria.

Gram-negative bacteria probably all have the same kind of communication molecules We focused on the PQS [Pseudomonas Quinolone Signal] Pseudomonas aeruginosa molecule because it was the first discovery and the best studied, Yong said. Other Gram-negative species, such as E. coli, could transfer their own communication molecules in the same way.

Learning more about how Gram-negative bacteria communicate with each other can help researchers better understand multi-species interactions and eventually control these types of high-risk infections.

"This study demonstrates the value of interdisciplinary work," Schertzer said. "We had reached a limit with what we could do experimentally, and we needed Dr. Yong's model to explain how the molecule was interacting with the membrane.More importantly, this work has generated a host of new questions as we continue to investigate. "

The study, "Molecular conformation affects the interaction of Pseudomonasquinolone signal with the external bacterial membrane", was published in the Journal of biological chemistry.

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More information:
Ao Li et al., Molecular conformation affects the interaction of Pseudomonas quinolone signal with the outer membrane of the bacterium. Journal of biological chemistry (2018). DOI: 10.1074 / jbc.AC118.006844