U.S. researchers say they're learning more and more about the importance of "on/off switches" that can determine whether bacteria remain harmless to humans or can suddenly turn deadly.
We don't necessarily think of bacteria as a social, communicating form of life, they say, but the single-cell organisms, utilizing a signaling process known as "quorum sensing," can in fact modify their behavior based on their population level within the human body.
In other words, researchers at the University of Wisconsin-Madison report in the journal Chemistry & Biology, some bacteria can conduct a "census" and be "aware" how many are present, then alter their behavior accordingly.
When such quorum-sensing types of bacteria grow to certain population levels, they may turn from harmless to pathogenic or change from helpful, even necessary, to unhelpful and unhealthy, the scientists say.
Chemistry Professor Helen Blackwell says the ability to block such a sensing signal could keep harmless bacteria from turning downright nasty.
She has been creating artificial compounds that have the ability to block the natural signal from binding with its intended protein target.
Blackwell and her colleagues have succeeded in converting an activation quorum signal into a deactivation signal and vice versa, a university release reported.
"It was surprising that making minor tweaks, very subtle changes, to the protein would convert a compound from an inhibitor to an activator, or turn an activator into an inhibitor," she says. "That shows that small-molecule control of quorum sensing is very finely tuned, much more than we even expected."
Many bacteria use such a sensing strategy, and it makes sense for them, the researchers say. While several hundred bacteria have no hope of overwhelming a host organism, and staying inert and evading the host's immune system is therefore an effective survival strategy. When their numbers increase into the millions it brings the ability to overwhelm the immune system and multiply even more rapidly.
Inhibiting the sensing capability in a strain of bacteria would offer another option in the war against pathogenic varieties, Blackwell says.
"We are approaching the end of the antibiotic era, as bacteria evolve resistance to some of our most advanced drugs, and scientists are looking for alternative ways to control bacteria," she notes.
While antibiotics are meant to kill off microbes, the strategy of controlling quorum sensing could maintain them in a harmless, "tame" state, she says.
That could help reduce microbial infections without increasing the drug resistance making such infections so problematic today, she explains.
