Microbiology Lecture 6

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Biofilms

  • Biofilms are morphologically heterogeneous and multi-layered matrices commonly established by sessile bacteria able to attach to surfaces and also each other.  
  • Due to the energetic cost of adhering to and departing from a mature biofilm, the mechanism is strategically controlled.
  • Biofilms are surface-attached communities of bacteria, encased in an extracellular matrix of secreted proteins, carbohydrates, and/or DNA, that assume phenotypes distinct from those of planktonic cells.

Formation of biofilms in nature

Biofilms offer their member cells several benefits:

The trapped cells can be exposed to toxic by-products, and also mass transfer limitations.

If external environmental conditions change, residents of a mature biofilm can be threatened. Under these circumstances bacteria respond by returning to their free-living lifestyle (planktonic) enabling them to disperse and re-colonise an alternative niche 

Applications

  • To purify water in water treatment plants.
  • To break down chemicals often toxic.
  • To produce biomolecules, including drugs.

Formation of biofilms in nature

  • Over 90% of all bacteria live in biofilms.
  • Biofilms are diverse from their formation on teeth as plaques and submerged rocks in a stream

Biofilms can be found:

  • On humans
  • Plants
  •  Animals
  • Environmental, industrial or medical systems. 

Biofilm phenotype

  • A slower growth rate
  •  Increased antibiotic resistance
  • Elevated frequency of lateral gene transfer 
  • Chemotaxis
  • Motility
  • Transport/uptake systems
  • DNA release
  •  Polysaccharide production (EPS), 
  • P limitation, 
  • Cellulose 
  • Alginate

Polysaccharides

They impact on microbial virulence significantly. They determine biofilm architecture by protecting the cells from the host defenses and antimicrobials.

Bacteria have capsular…

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