Biofilms Flashcards
What discovery was made in 1933?
Arthur T Henrich discovered that water borne bacteria were not living on their own, they were living together. Shows that although “biofilm” is a fairly new term, the concept of microbes working together is not new.
What happened in 1934?
Claude E Zobell and Esther C Allen found marine bacteria forming on submerged surfaces- they defined a biofilm.
What is the definition of “biofilm”?
Sructured community of microbial cells encased in an extracellular matrix and adherent to each other or a surface.
A highly regulated process.
A ubiquitous behaviour exhibited by microbes.
Where can biofilms be found?
Everywhere- some can be environmental (microbial mats at Yellowstone National Park), some can cause disease (plaque, contact lens infection).
What molecules can biofilms make?
Extracellular polysaccharides, lipids, proteins, DNA.
Many molecules are functional amyloid (large polymers).
Allow adhesion to each other and surface.
Polysaccharides have several functions- signalling, adhesion, provide mechanical pressure, structure, absorb water and nutrients.
What are the advantages of forming a biofilm?
Strength in numbers. Resist antibiotics. Withstand environmental fluctuations. Resist physical force. Evade immune system. Sometimes allow different species of bacteria to live close together- other species can use resources that are waste or dangerous to another species.
How can we take advantage of biofilms?
Use biofilms to break down waste material in sewage plant.
Intestinal biofilm can extract nutrients.
Biofilms on plant roots- promote growth or protect from pathogens.
Biological fuel cells.
Why are biofilms a major problem on medical devices?
Antobiotic treatment is ineffective.
What kinds of infections can occur from biofilms on human tissue?
Urinary tract infcetion, cystitis, recurring infections on heart valves- need to be removed and replaced.
What are the differences between biofilm cells and free-swimming cells?
Biofilm cells are genetically identical.
Gene expression is vastly different.
(Biofilm and planktonic bacteria are in different states. Can respond to physical environment).
How could you identify genes involved in biofilm formation?
Knockout genes and see if biofilm can’t form.
Look at transcription levels of known targets using fluorescent reporters.
Transcriptional assay- next gen sequencing in bf+ and bf-, proteomics.
How is antibiotic resistance/tolerance achieved in biofilms?
Access to microbes is blocked (physical barrier).
Microbes can pick up antibiotic resistance cassettes by DNA exchange.
Different physiological state- can be less susceptible to antimicrobials.
Different stress responses.
Persister cells- go into a dormancy state. Not actively growing, so not affected by most antibiotics that need actively growing cells to work.
ECM can neutralise some antibiotics.
Can get mixed microbial communities- species could be resistant to diffreent antibiotics, meaning multiple antibiotic won’t work to clear infection.
How do microbes interact?
Physical interactions. Chemical changes (eg. quorum sensing). Use of metabolic by-products. Changes in environment. Alteration of host immune response.
What happens in polymicrobial infection of the lung in cystic fibrosis?
CF is caused by mutations in the CTFR gene, which makes defective chloride ion channels. This affects chloride ion transport in cells, which causes a viscous mucus layer to build up in airways. This can harbour microbes which can form a biofilm in the lungs.
Colonisation and establishment of chronic infections ultimately leads to the morbidity and mortality associated with CF.
Immune response is compromised, Pseudomonas aeruginosa biofilms are able to colonize the alveoli, and to form biofilms.
What is quorum sensing?
Cell-cell signalling systems to coordinate gene expression. Signal molecule is produced by one bacterium, and the signal is picked uo by another.
Signals can be intra or inter species.
