Researchers have discovered a new type of flagella that is capable of digesting proteins in the bacteria’s environment. This is the first known example of a type of flagella that acts enzymatically. The discovery was made by researchers at the University of Waterloo and was published in a paper that appeared this week in Nature Communications.
Flagella are found in a wide range of bacterial species and display a large amount of sequence diversity corresponding to the unique environments bacteria are adapted to. It was this diversity that led the scientists to question whether there may be undiscovered functions of flagella to explore.
To answer their question the researchers turned to bioinformatics. They gathered a database of tens of thousands of predicted flagellin structures and combed it for novel domain architectures. This search revealed several types of flagellins with enzymatic activity.
“What we found in this case is that many bacteria have repurposed their flagella to function as protein-degrading enzymes. There are thousands of these enzymes, making this potentially one of the largest enzyme structures known," said Andrew Doxey, a professor of biology at the University of Waterloo, and the lead researchers on this study. He and the other researchers believe these enzymatic flagellins may help bacteria move through viscous environments.
To test the activity of these new flagella, the researchers isolated flagella from Clostridium haemolyticum, a pathogen that can be fatal to cows and sheep and is known to have numerous flagella on one cell. They found that these flagella were capable of breaking down proteins in a cow's liver—the main site of infection for this pathogen.
These enzymes were also found in bacteria that inhabit the human gut, though further research is needed to know what role they play there.
This knowledge may improve understanding of disease and could potentially be used in biotechnology for degrading structures we want to break down, including biofilms.