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No matter how many times it’s demonstrated, it’s still hard to envision bacteria as social, communicating creatures.
But by using a signaling system called “quorum sensing,” these single-celled organisms radically alter their behavior to suit their population. In short, some bacteria “know” how many of them are present, and act accordingly.
Blocking such a signal can prevent a bacterium from turning, in common language, nasty.
海伦·布莱克韦尔，教授 化学 at the 大学 of Wisconsin-Madison, has been making artificial compounds that mimic the natural quorum-sensing signals, including some that block a natural signal from binding to its protein target.
In research published today in the journal Chemistry & Biology, Blackwell changed key building blocks in these protein targets one by one. “If that part of the protein is important, the change will have a significant effect on our signal’s activity,” she explains.
Quorum sensing can also direct soil bacteria that infect soybean roots to harvest nitrogen from the atmosphere and improve crop yields.
Reducing infectivity may allow the immune system to help clear the pathogen, Blackwell says. In procedures such as hip replacement or burn treatment, where infection is common, “this could be used prophylactically, or to augment and extend the lifetime of antibiotics.”
The study was performed on Gram-negative bacteria, which are well protected from many drugs by a double membrane. “They also have lots of nasty pumps that eject those drugs that do enter,” Blackwell says.
Gram negatives include E. coli, salmonella, shigella, and pseudomonas. Members of the group cause cholera, gonorrhea, meningitis, Legionnaire’s disease, and respiratory and gastrointestinal diseases.
Gram negatives “are probably the most challenging infections, and the drugs that we have are really failing,” Blackwell says. “But there is also a fascination in seeing how these very simple organisms team up to do things that are impossible in small numbers.
“The compounds and protein modifications we identified in the current study will serve as useful research tools to elucidate, and perhaps redirect, their ‘tiny teamwork.’”
Story by David Tenenbaum, 大学 Communications
Light switch photo courtesy of kelly.sikkema