Question

Bacterial Flagella

Many pathogenic bacteria that infect the intestinal tract have flagella. (Hint: See Flagella, section F.)

1. Why might having flagella better enable those bacteria to cause disease?

2. Most pathogenic spirochetes such as Treponema pallidum and Borrelia burgdorferi disseminate from the original infection site. How are they able to do this?

Answer 1

Answer 1) Flagella gives the ability of motility to bacteria. Mobile bacteria can seek new and variable sources of nutrition and away from damaging agents and also help the pathogenic bacteria to spread from one spot to another. Therefore, flagella is usually considered as a virulence factor. Flagella may sometimes also act as adhesins for several bacteria such as E.coli. They also play a crucial role in attachment, colonization of host tissues such as mucus membranes, biofilm formation and transport of molecules associated with virulence. The flagellar apparatus also increases the chance of encounter with host cells and facilitating the invasive capacity.

Answer 2) Borrelia species (spirochetes) disseminate using axial filaments known as endo-flagella. The bacterium moves in a cork-screw like motion with filaments rotating in space between peptidoglycan layer and outer membrane.

Treponema pallidum has a helical structure which allows it to move in a similar corkscrew type manner and enter mucous membranes.