Biofilms Flashcards
What are microbial biofilms?
A group of microorganisms which are adherent both to each other and to a surface.
Bacteria within biofilms are frequently embedded in an ECM that holds the organisms together
What are microbial biofilms made from?
-Number of polymeric substances of bacterial origin like polysaccharides, proteins and nucleic acids
-Biofilms represent the typical mode of growth of bacteria in natural environments
-The biofilm lifestyle contrasts w the planktonic (suspended growth) lifestyle
Cycle of candida albicans - fungi
- Adhesion - initial contact w surface-reversible
- Initiation - chemical messaging - switch to hyphal growth
3.Maturation - hyphal interwoven structure - anti fungal resistnce - Dispersal - dissemination - clinical challenge
Where do microbial biofilms enter?
Catheter, hip replacement, peridontal disease
Cycle of pseudomonas aeruginosa
- Adhesion
- Microcolony - chemical messaging- microcolony formation
- Maturation - 3D structure formed
- Dispersal - dissemination - clinical challenge
Can biofilms be polymicrobial in nature?
Yes - many diff types of species of bacteria
Where does vibrio cholerae form biofilms?
In aquatic environments prior to entry to a host
Where does opportunistic human pathogen Pseudomonas aeruginosa form biofilmss?
Within the airways of cystic fibrosis sufferers
Example of polymicrobial biofilm?
Dental plaque
Can fungi form biofilms?
Yes
Why is the formation of biofilms important?
-Promotion of bacterial survival
-Permitting bacteria to remain in a favourable niche
-Close proximity within the biofilm provides more opportunities for nutrients and genetic exchange between organisms
How does biofilm formation promote bacterial survival?
More tolerant to antimicrobial substances including host defence compounds, bleaches, antibiotics
-Some antibiotics have reduced penentration into the biofilm structure
-Bacteria within biofilm grow more lsowly than their planktonic counterparts
-Bacteria in biofilms show diff patterns of gene expression than planktonic cells with enhanced expression of genes conferring tolerance to antimicrobial substances
Look at diagram on chemical and physical interactions between bacteria and other cells in biofilm
Steps in the formation, maturation and dispersal of biofilms?
-Attachment of planktonic cells to a surface using pili, flagella, adhesion proteins
-Colonisation and cell-cell adhesion by the extracellular matrix
-Proliferation and maturation, further matrix production
-Dispersal to release planktonic cells - this may be triggered by nutrient availability or other environmnetal factors
How to control biofilm formation?
-Inhibition of regulatory systems that control biofilm formation through low molecular weight molecules
-Use of enzymes that degrade the components of the ECM
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What controls biofilm formation in Pseudomonas aeruginosa?
Quorum sensing by 3-oxo-C12 HSL and 4-Alkylquinolones (PQS and HHQ)
Furanone C30 potentiates the antibiotic effects pf tobramycin on biofilms of Pseudomonas aeruginosa - green - live, red - dead
Can microbial compounds from one pathogen block biofilm in co-colonising pathogens?
Yes
-Clinical isolates sensitive to small molecule analogue
