What is a Biofilm?
¡A ____ of microbes adhering to ____ ____ and a ___ ____, and encased in a sticky ____________.
¡A community of microbes adhering to each other and a solid surface, and encased in a sticky exo-polysaccharide (EPS) matrix.
Where do they form?
¡Non-shedding, fluid coated surface, in a non-sterile environment----> Biofilm
Why do we care?
- ____ ____
- §Medicine and Dentistry
- ▪___ infections
- ▪Difficult to _______
§Natural process of decay
§Bioremediation of toxic waste
§Medicine and Dentistry
▪Difficult to remove from surfaces
How do biofilms form?
¡3-Growth,co-aggregation, matrix (EPS) production
¡4-Mature biofilm (climax community)
Adhesion is a major factor in biofilm formation
____ ____, _____ binding,
§_____ to a surface
___ ___ ___forces
§Non-specific, reversible binding,
§Attraction to a surface
§Van der Waals forces
¡Usually mediated by bacterial ___ ___--> _____
§Adhesins recognize surface molecules on the___ ___--> _____
§Provides ___ and ____
¡Usually mediated by bacterial surface proteins- Adhesins
§Adhesins recognize surface molecules on the binding target - Receptors
§Provides specificity and permanency§
Adhesin - Receptor Interactions
___ ___ (____)
___ ___ ____
____ ___ (____)
¡Carbohydrate - Protein- Carbohydrate
¡Other combinations (lipids)
¡_____-___ ____ ____ ___
_____-____ that bind ___
___ ____ ____ - Gram ___ outer membrane, ______
_____ _____- ____
¡Fimbriae-hair like surface appendages
¡Lectins -proteins that bind sugars
¡Lipo-teichoic acid - Gram + outer membrane, glycolipid
¡Extracellular polymers- capsule
- ____ ____ on ___ cells
¡Sialic acid on mucosal cells
Colonization of surfaces
¡Some bacteria ___ ____ __ ____
Adhere to ___, ____ ___
¡Other bacteria adhere to ____ ____
§You might see these terms used inter-changeably
¡Some bacteria adhere well to surfaces
§(Pellicle, soft tissues)
¡Other bacteria adhere to pioneer bacteria
§You might see these terms used inter-changeably
Visual coaggregation scores for different pairs of strains.
Visual coaggregation scores for different pairs of strains. Cells were grown to stationary phase and harvested after 36, 71, or 144 h. Sphingomonas sp. strain 2.10 and Afipia sp. strain 2.2 (36 h) showed a score of 0 (no coaggregation), P. marcusii 2.21 and B. natatoria 2.3 (72 h) showed a score of 1+, Sphingomonas sp. strain 2.18 and Afipia sp. strain 2.2 (144 h) showed a score of 2+, B. natatoria 2.1 and Nocardioides sp. strain 2.20 (144 h) showed a score of 3+, and B. natatoria 2.1 with M. luteus 2.13 (72 h) showed a score of 4+. Bar, 1 cm.
Corncob and Bristle-brush
How do biofilms form III
¡Growth-microcolonies form community
¡Matrix synthesis (EPS)
Dental plaque. Coloured scanning electron micrograph (SEM) of a fracture through a tooth showing dental plaque (top) and dentin (bottom). Plaque consists of a film of bacteria embedded in a glycoprotein matrix. The matrix is formed from bacterial secretions and saliva. Plaque is the main cause of tooth decay. The bacteria feed on sugars in food, producing acid as a waste product. This acid corrodes the teeth's enamel coating, resulting in dental caries. A build-up of dental plaque can also lead to inflamed and infected gums. Severe gum disease can lead to teeth falling out. Dentin is mineralised connective tissue, that makes up the majority of the tooth. Magnification: x350 when printed at 10 centimetres wide.
___ ___, or “____”
¡Secreted by biofilm bacteria to form a___,____ layer around bacteria
¡Made of ____ ____, allows ____
¡Exact composition ______
¡Biofilm matrix, or “slime”
¡Secreted by biofilm bacteria to form a cohesive, protective layer around bacteria
¡Made of polysaccharide gel, allows diffusion
¡Exact composition varies depending on bacteria present
The EPS Matrix
Mature Biofilm Structure
____ is key to survival of bacteria in biofilms
¡Diffusion is key to survival of bacteria in biofilms
Properties of a Biofilm
Affects of Structure on Biofilm
Species with ___ ____ can live together
Species with different requirements can live together
How do Mature Biofilm Communities Interact?
- __ ___-
- bacteria cooperate in the____ of ____
- ____, ____
- ___ ___
- share ____ ____ genes
- ____ ____-
- bacterial _____
¡Food webs-bacteria cooperate in the breakdown of nutrients
¡Gene transfer-share antibiotic resistance genes
¡Quorum sensing-bacterial coordination
Beneficial Nutritional Interactions in Plaque
Step and Actinomyces break down sugar to lactate
Veillonella in same vicinnity of strep because it eats lactate
Biolfilm Protects against
Five Mechanisms of Increased Biofilm Tolerance to Antimicrobials
¡Antagonism-the production of compounds to ____ __ ____of other organisms
____-small ____ that ___ __ ___in the ____ of other bacteria
▪produces ___, to lower ___ to ___
▪Produces ____ that kill other Streptococcus spp.
¡Antagonism-the production of compounds to inhibit the growth of other organisms
§Bacteriocins-small proteins that poke a hole in the membrane of other bacteria
▪produces acids, to lower pH to ~5.5
▪Produces bacteriocins that kill other Streptococcus spp.
- ¡Different bacteria in close contact may ___ ____
- ___ ____
- ▪_____. share ____resistance genes in biofilms
- ____ ___
- §What are the three forms of DNA exchange between bacteria?
¡Different bacteria in close contact may share DNA
▪Prevotella spp. share tetracycline resistance genes in biofilms
§What are the three forms of DNA exchange between bacteria?