Stanford researchers reveal how some bacteria go "underground"

Bioengineers at Stanford University have unlocked a mystery that had spanned over six decades: why some bacteria shift their shape for some time, fooling the immune system, and recover their original form later.

This enigma was first observed by Nobel Prize-winning geneticist Joshua Lederberg in the 1950s, when he saw some bacteria were able to shed their outer walls, turning themselves into a blob, and go under the radar inside the body.

Lederberg also noticed that these bacteria later regained their outer shells along with their full infectious potential.

In order to solve the riddle, Stanford bioengeneering professor K.C. Huang and colleagues from Stanford and Princeton used a time-lapse microscope to shoot detailed pictures of E. Coli bacteria for over nine hours.

What they discovered was that a protein, MreB, known to play a key role helping the cells create their outer wall, was also crucial when the cells wanted to stop "going undercover" and revert to their normal shape.

When infused with a specific antibiotic that suppresses MreB, the cells recovered their hard walls, but this time, shaped like a blob. Unable to maintain this form, the cells eventually died out.

"What we found was very stark: MreB was critical for this reversion process to occur, and without MreB what would happen is that the cells would just expand in size without any notion of their normal shape," Huang said in a press release.

According to the researchers, this discovery gives an essential insight into how cells maintain their structure, and it also opens the door to understanding why some bacteria become resistant to certain antibiotics over time.

Many antibiotics, Huang explained, target the cell walls, but since the cells can get rid of their outer walls, they continue to reproduce and survive in the shape of blobs until they revert to their original form.

"Better understanding of cell wall construction could lead to better antibiotic strategies," Huang said.

The researchers describe their findings in the latest issue of Molecular Microbiology. Endi