Until now, that is. Lorenzo Talà, a PhD student in the lab of Alexandre Persat at EPFL's Institutes of Bioengineering and Global Health has developed a microscopy method that can directly observe the structures many bacteria use to crawl.
"Bacterial surfaces are decorated with protein filaments involved in motility, adhesion, signaling and pathogenicity, which ultimately rule how bacteria interact with their environments" says Talà. "However, they are so small that observing them in live cells is extremely complex. So we are left with little knowledge of their dynamic activities."
Structures - IV - Pili - Filaments - Surface
This is especially true for structures known as "type IV pili": nanometer-wide filaments that extend and retract from the surface of many bacteria, helping them walk in a way known as "twitching motility." The term might not sound very serious, but it mechanically activates virulence in certain pathogens -- meaning that it is a prime target for fighting them.
The scientists studied the bacterium Pseudomonas aeruginosa, an opportunistic pathogen that is commonly found in soil. It is one of the most medically concerning bacteria: a leading cause of hospital-acquired infections and of serious infections in cystic fibrosis, traumatic burns, and immunocompromised patients, it is now ranked #1 in the World Health Organization's antibiotic resistant watch-list.
Bacteria - IV - Pili - Motion - Power
But do single bacteria orchestrate type IV pili motion to power their motility? "In our studies of type IV pili and mechano-activation of virulence in Pseudomonas aeruginosa, one technical paradox has been a source of frustration: pili, but also fimbriae, flagella, and injection systems permanently extend outside single cells, so why can't we directly visualize them?"
To overcome this, the scientists explored an emerging microscopy method pioneered by their collaborator...
Wake Up To Breaking News!