Dr. Igboin Study Guide 1 Flashcards
Biofilms
Organized multicellular communit attached to a living or inert surface, surrounded by a self-produced extracellular polymer matrix
Biofilms role in infections
Most bacteria exist in biofilms in nature. They provide biodiversity and can spread to other areas in the body, which is easier than creating a secondary infection
Steps in Biofilm formation
1) Contact to surface and reversible absorption
2) Irreversible attachment
3) Multiply and recruit other bacteria
4) Exopolymer produced by colonies
5) Incorporaiton of other bacteria
Surface conditioning
Important for biofilm attachment
Absorption of organic molecules onto a clean surface forms a conditioning film to which bacteria adhere
Secondary colonizers
Bind to F. nucleatum and rely on the metabolic waste products of primary colonizers
Structure of a Mature biofilm
75-95% Extracellular 5-25% bacteria
Numerous bulbous micro-colonies with fluid filled channels
Fluid filled channels in biofilm
Carry nutrients, fluid, waste, etc between bacteria colonies
How are microcolonies organized
Based on what their needs are…for example, aerobic colonies may be near the exterior, while anaerobic colonies may be closer to the attachment surface
How do biofilm bacteria spread
Bacteria are released either actively (by ExoP) or passively (by fluid flow, collision, human intervention) and become new pioneer cells
Advantages of biofilm to the microbes
Harder to clear
Resistant to antimicrobials and host defenses
Resistant to mechanical removal
Nutritional advantages
Advantages of biofilm to the host
Colonization of beneficial species in a biofilm can compete for space with harmful species as well as produce molecules that can kill harmful bacteria
Quorum Sensing
Process of cell-cell communication by which bacteria monitor the density of members of their species and other species in the environment
Purpose of Quorum Sensing
To synchronize behaviors that cannot be accomplished by individual bacteria working alone
Quorum Sensing in Gram Negative bacteria
When there is enough LuxI made outside the cell, it diffuses into the cell.
Inside the cell, it binds to a signaling protein, which binds to the DNA/Target gene
Species specific
Quorum Sensing in Gram positive bacteria
Oligopeptide on the outside of the cell binds to a surface receptor
Whe bound, the surface receptor activates a gene expression activator protein
The gene expression activator protein binds to the DNA and expresses a gene
