biofilms Flashcards
what is a biofilm
when bacteria attach to a surface and grow there
what are exopolysaccharides
The matrix in which bacteria grow in a biofilm. 90% of the biofilm is made up of the EPS rather than the cells themselves
what are the four stages in biofilm development
Attachment
Colonisation
development
active dispersal
how do cells attach to a surface to form a biofilm
the bacteria collides with the surface by random chance. Surface structures on the bacteria, often flagella, stimulate adhesion.
Adhesion stimulates the activation of biofilm genes that synthesise the matrix that holds a biofilm together.
Once committed to a biofilm cells often lose their motility.
why are biofilms advantageous
They can protect against predation by protists and small grazers
they can trap nutrients for microbial growth
they prevent bacteria from being washed into a less favourable habitat
Since horizontal gene transfer is happening all the time, bacteria are more resilient to antimicrobial agents
what are microbial mats
huge biofilms often 5-10cm thick. They usually occur in extreme environments, either acidic or hot, due to the absence of predators
what is dental plaque
dental plaque is a biofilm
explain why there is such diversity within biofilms
bacteria in biofilms create mutualistic relationships with eachother. Aerobic bacteria will colonise the outer layers whilst anaerobic bacteria will colonise the inside and produce hydrogen sulfide. more bacteria that reduce hydrogen sulfide can then colonise these areas
how does dental plaque form on teeth
acidic glycoproteins found in saliva form layers round teeth which bacteria, usually streptococci, can attach to. if they build up they will form plaque
how are biofilms involved in human disease
cystic fibrosis is characterised with the formation of biofilms in the lungs. these are especially dangerous since the biofilm makes it hard for antibiotics to reach their targets.
why are biofilms more resistant to antibiotics
they grow slower, the matrix prevents antibiotics from penetrating and horizontal gene transfer occurs more frequently.
what is Endochartitis
the infection of hear chambers or valves. These often occur because a biofilm was growing on the replacement valve
how are medical implants designed to prevent the growth of biofilms
-anti adhesive surfaces
-wear resistance
-bactericidal coatings
-coatings the stimulate the bodies natural tissues to integrate
what is biofouling
the accumulation of microorganisms, plants, algae or animals on equipment which leads to its deterioration
