· Sticky, polysaccharide encased film of microbes on a surface
o Free microbes adhere to surface, sometimes aided by organic molecules
o Binding to surface triggers production of extracellular slime that attaches
o Grow and become encased
o Others join them fixing to them or slime
· Not haphazard but complex
o Architecture depends on
§ Supply and flow rate of nutrients
§ Growth rate of biomass and form
§ Rate of detachment from biofilm
· Low nutrient flow rate or nutrients quickly used
o Finger-like or mushroom like structures with holes and channels
· Sufficient nutrient flow rate
o Compact structure with less form
· Nutrients and waste flow through open channels
Projections break off and seed colonization at other sites
o Allow microbes to work in concert and adapt
o Very common
§ Sticky
§ Coat protects from environmental and chemical factors
§ All function together
o Important in industry
o Cause metal corrosion
o Clog pipes
o Unwanted source of microbes
o Form in suction devices, sinks, faucets, in dental offices
o Many infections caused by biofilms
§ Catheter induced septicemia and skin infections
§ Artificial heart valves, implanted knees
§ Dental plaque
o Difficult to treat due to increased resistance to
§ Antibiotics
§ Antimicrobial chemicals
§ Host immune responses
§ 100x – 1000x more resistant
§ Why?
· Can’t penetrate
· Quorum sensing activated genes for membrane efflux pumps, pump stuff out
· Conjugation and transformation readily happening
o Chronic and difficult to eradicate
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