Biofilms Flashcards
What is a biofilm?
A mixed community of bacteria growing on a surface
How do biofilms adhere to a surface?
Polysaccharide matrix and adhesins
What is the structure of a biofilm?
Very complex. The surface is lumpy and uneven and lots of channels throughout
How are oxygen and nutrient gradients found through biofilms?
Cells at the surface have the highest access to oxygen and nutrients, so they do aerobic respiration. Oxygen and nutrients get depleted further into a biofilm because the cells use it up
What’s the problem with living in the middle of a biofilm?
No oxygen, so its a great place for obligate anaerobes, but there’s also no nutrients
How do biofilms get around the nutrient depletion in their centres?
Cells in the middle will often metabolize each other’s metabolic byproducts
What are 3 reasons why bacteria form biofilms?
Protection, close association with neighbours, adhesion
How does being in a biofilm protect the cells inside?
Provides physical protection and the matrix acts as a chemical barrier. Biofilms are also resistant to phagocytosis
How is being in a biofilm good for attachment to surfaces?
Allows a cell to remain in a favourable location and avoid being washed away
How does being in a biofilm allow close association between neighbouring cells?
Cell to cell communication is easier. Also allows high rates of horizontal gene transfer to occur and lets cells use each other’s metabolic by products
Why are biofilms a problem on medical implants?
Biofilms can form on abiotic surfaces like medical implants quite easily and cause recurrent and resistant infections. Fragments of the biofilm can also break off and colonize other parts of the body. Antibiotics also can’t penetrate and completely eradicate the biofilm, so the only way to get rid of it is to replace the medical implant
How do dental biofilms cause cavities?
Bacteria can attach to saliva proteins on the surface of your teeth and form biofilms. If you’re eating sugar, they ferment it into lactic acid and the biofilm matrix traps it next to the tooth, where it dissolves your enamel and causes a cavity
Why can’t biofilms in pipes be removed by chlorination?
Only kills the cells on the surface
Why do water safety tests often miss biofilms in pipes?
They only detect what has broken off from the biofilm, so it gets missed and keeps building up
How does the ACU pilus of Acinetobacter baumanii work?
It was 3 hydrophobic “fingers” at its tip that interact with other hydrophobic surfaces non-specifically
