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San Diego Scientists Discover A Bacteria’s Weird Napoleon Complex

Why does one of the smallest organisms known to science have such an outsized ability to conquer our immune systems? Scientists at The Scripps Research Institute in La Jolla found out in an unexpected discovery.

In a paper published in Science, Rajesh Grover and his colleagues describe a protein used by the bacteria M. genitalium to ward off virtually all the antibodies the human immune system can throw at it.

Photo by The Scripps Research Institute

Protein M latched on to every antibody Scripps scientists threw at it, which could explain why the bacteria they studied is so good at infecting hosts.

"They're the smallest living organism on this planet," he said. "They cause sexually transmitted diseases in humans."

The bug is a little guy — very little. It only has around 500 genes. Yet, like Napoleon, it punches much hits hard for its size. It's able to establish longterm infections in humans.

Grover and his colleagues discovered the secret weapon M. genitalium uses to fend off our body's antibody armies. They call it "Protein M," a molecule that hasn't been identified until now. What's remarkable about Protein M, according to Grover, is its tenacity.

"We were really surprised when we saw the structure of the protein," he said. "By binding to each antibody, the protein makes the bacterial invader 'invisible' to our natural defense system. No other molecule is known to have such sophistication in basically hijacking our immune system."

Grover said these are very early insights, but they could one day lead to new methods for fighting bacteria. The antibiotics we have now now are becoming less effective over time, and Grover sees Protein M as an interesting target for new drugs.

"It's going to tell us a lot about our understanding of other bugs as well," Grover predicted.

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