MicroL10 Biofilms

• Biofilm formation is a survival strategy

- May be the default mode of growth in natural environments where nutrients are limited

Biofilms enable bacteria to live together

- Permits cell-to-cell signaling, genetic exchange

Persister cells:

cells tolerant to antibiotics due to a state of dormancy

Stress response:

inner layers have more time to adapt

biofilm flow chamber system

media bottle, pump, bubble traps, flowcell, effluent-bottle

Altered microenvironment:

nutrient depletion creates zones of altered activity

Slow penetration:

outer layers of biofilm cell absorb damage

biofilms impact

teeth, drinking water, oil recovery, paper manufacturing, medical implants, ship hulls, food processing

Homoserine lactone-

wont be able to reach high enough conecntrations when free floating, but in a biofilm, In a biofilm, if molecules being freely diffused, possinbilty that some cells are gonna influence the whole biofilm, they are talking to one another

Biofilms are a means of microbial self defense

- Cells can resist physical forces, phagocytosis, antibiotics

endocarditis

-chronic infection where staphylococcal biofilms are formed on the surface of heart valves

• More than XX% of all microbial infections involve biofilms

60%

Traditional methods to grow bacteria

Agar plate Liquid culture

The importance of biofilms in medicine

Bacteria that form biofilms cause persistent (chronic) infections. In this state the bacteria can withstand the action of the host defense system as well as the highest deliverable doses of antibiotics.

Why do bacteria form biofilms?

Biofilms are a means of microbial self defense • Biofilm formation allows cells to colonize favorable niches Biofilms enable bacteria to live together • Biofilm formation is a survival strategy

Staphylococcal biofilms

Often associated with biofilm formation on the surface of implanted medical devices

• Biofilm formation allows cells to colonize favorable niches

Cells remain attached to nutrient rich surfaces or in locations where nutrients are continually replenished

viewing biofilms

Light microscope Scanning confocal laser microscope

Pseudomonas aeruginosa and cystic fibrosis • Virulence factors:

P. aeruginosa alters gene expression during biofilm growth • Virulence factors: - Extracellular polysaccharide (alginate) - Extracellular DNA (DNases used in treatment) - Quorum sensing

Pseudomonas aeruginosa and cystic fibrosis

P. aeruginosa colonizes the lung of cystic fibrosis patients & forms biofilms

How do biofilms become so resistant to antimicrobials?

Slow penetration: Stress response: Altered microenvironment: Persister cells: Antimicrobial depletion:

Green fluorescent protein (Gfp)

Tagging of cells, multiple colours Direct monitoring of live cells No need to stain!

A biofilm is

a structured community of bacterial cells enclosed in a self-produced matrix and adhered to an inert or living surface

quorum sensing

ability to reaqct to a crowd of bacteria

Antimicrobial depletion:

adsorption of antibiotics, lack of penetration

Examples of Biofilms

• Pseudomonas aeruginosa and cystic fibrosis • Uropathogenic Escherichia coli and catheter infections • Staphylococcus aureus and endocarditis

Examples of Biofilms living tissues

• Tooth enamel • Heart valves • Lung • Middle ear • Bladder

Examples of Biofilms medical devices

• Urinary catheters • Central venous catheters • Contact lenses • Heart valves • Prosthetic joints