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Biofilm_growth_structure_function_ppt.pdf
- 1. Biofilm growth, structureand function OEST 740 011508
- 2. Biofilm basics Biofilm basics •Biofilms are now believed to be the primary mode Biofilms are now believed to be the primary mode of existence for bacteria in aqueous environments. – 1,000 – 10,000x greater populations than planktonic • Defined as a consortium of microorganisms encased in a complex 3-D gelatinous matrix of t ll l t i l t d b th i h biti extracellular material secreted by the inhabiting organisms. • The establishment maintenance and existence of • The establishment, maintenance and existence of biofilm communities are highly complex, socially organized processes. organized processes.
- 3. Biofilm biology Biofilm biology •Investigates the consequences of the close Investigates the consequences of the close association of microorganisms at interfaces. – Physiological adaptation to the proximity of other cells and surfaces. • Biofilms are highly diverse in nature i i l • Common principals – Attachment C dh i – Coadhesion – Regulation of biofilm phenotype – Biofilm architecture Biofilm architecture
- 4. Interfaces Interfaces • Solid:Liquid q – Mostcommon type of biofilm • Gas:Solid (often exposed to liquids) – Lichen, trickling filters, myxobacterial swarms • Gas:Liquid Neuston penicillin produced by fungal fermentation – Neuston, penicillin produced by fungal fermentation • Liquid:Liquid – Hydrocarbon oxidizing biofilm at oil:water interfaces y g • Solid:Solid (periodically exposed to liquid) – Endolithotrophic communities
- 5. Biofilm impact Biofilm impact •The development of biofilms has important The development of biofilms has important impacts – Bacterial properties p p • Virulence • Survival • Diversity – Settlement and metamorphosis of higher organisms organisms – The physical and chemical structure of the surfaces on which they are established y
- 6. Biofilm Impact Biofilm Impact •Thus, they are potentially relevant to a wide , y p y variety of disciplines that aim to study processes in aqueous environments – Oceanography – Ecology – Biology – Engineering – Medical – Dental
- 7. Biofilm Composition Biofilm Composition Ct % T t l D i ti O i i Component % Total Description Origin Water Up to 95% Characteristics determined by dissolved determined by dissolved solutes Microbial cells 2-5 % Pol saccharides 1 2 % Ne tral and pol anionic ; E tracell lar Polysaccharides 1-2 % Neutral and polyanionic ; homo and heteropolysaccharides Extracellular Proteins <1-2% Enzymes Extracellular and Proteins <1 2% Enzymes Extracellular and cell lysis DNA and RNA <1-2% Cell lysis Ions ? Bound or free Ions ? Bound or free
- 8. Exopolysaccharides • EPS presentin biofilms is thought to closely resemble the corresponding polymers synthesized resemble the corresponding polymers synthesized by planktonic cells. • Quantity of EPS depend on availability – Carbon (intra and extra-cellular) – Carbon:Limiting nutrient – Vary in proportions of various components – Vary in proportions of various components • Some are neutral macromolecules, but majority are polyanioninic p y – Uronic acids (D-glucuronic>D-galacuronic = D- mannuronic) – Ketal-linked pyruvate Ketal-linked pyruvate
- 9. Exopolysaccharides Exopolysaccharides • Very feware polycationic y p y – S. epidermidis • In nature, exist in ordered configurations of low temperature saline conditions temperature, saline conditions – Very long, thin molecular chains – Molecular mass 0.5-2.0 x 106 Da A i i f • Association of structure – Electrostatic and hydrogen bonding are dominate forces • Provide bacteria with backbone structure, measure of Provide bacteria with backbone structure, measure of homeostasis, primitive circulatory system and a large measure of protection
- 10. Formation • Biofilm formationbegins with a transition of bacteria from the planktonic (free swimming) form to its genetically distinct attached form genetically distinct attached form. • The genetic transition occurs across the life cycle of the biofilm and is comprised of seven distinct steps C di i i – Conditioning – Contact – Adsorption p – Growth – Production of extracellular products extracellular products – Attachment – Re-entrainment Photo: CEB : MSU-Bozeman Photo: CEB : MSU-Bozeman
- 11. Step 1: Conditioning Step1: Conditioning • A clean surface is immediately covered with a A clean surface is immediately covered with a conditioning film of organic molecules and macromolecules macromolecules. • Transport of molecules and small particles is rapid and as a result adsorption of conditioning rapid and as a result adsorption of conditioning film occurs instantaneously Th f h di i i fil l • The presence of the conditioning film alters the characteristics of the substratum.
- 12. Effect • Substrate Substrate hydrophobicity decreases • Substrateobtains a negative charge • Substrate potentials increase or decrease C i i l f • Critical surface tensions increase or decrease decrease
- 13. Step 2: Contact •Bacteria in fluid contact the substrate via mass transport mechanisms • Strongly influenced by mixing in the bulk fluid – Related to flow regime • Laminar flow transport p – Sedimentation – Motility – Molecular diffusion • Turbulent flow transport (larger particles) – Convection – Diffusive transport – Diffusive transport • Bacteria penetrate the viscous sublayer (~1 cm) via eddy diffusion • Bacteria acti el migrate thro gh the diff si e s bla er • Bacteria actively migrate through the diffusive sublayer using pili (~1 mm)
- 14. Step 3: Absorption Step3: Absorption • At the substrate the cells absorb reversibly or At the substrate the cells absorb reversibly or irreversibly – Primary (early) colonization Primary (early) colonization – mediated through specific or non-specific physiochemical interactions with components of conditioning film – Adsorption – accumulation of cells directly on surface f b of substrate – Desorption – re-entrainment of cells into the bulk fluid • Complex process • Complex process
- 15. Adsorption Adsorption • Initial adsorptionoccurs through long-range (100s Initial adsorption occurs through long range (100s nm), weak interactions with low specificity – Electrostatic or van der Waals forces Electrostatic or van der Waals forces • Irreversible adsorption is short-range (5nm), highly specific interaction highly specific interaction – Dipole, ionic, hydrogen bonding, hydrophobic interactions, etc. – Can take place by secretion of EPS or fibrillar structures
- 16. Step 4: Growth Step4: Growth • The number of irreversibly adsorbed cells The number of irreversibly adsorbed cells increase due to replication Limited by physiological processes – Limited by physiological processes – Concentration of rate-limiting nutrient important
- 17. Step 5: Productionof extra-cellular products • Affixed cells transition from planktonic form to attached form – Processes controlled by gene encoding for the production of products
- 18. Step 6: Attachment p •Secondary (late) colonizing cells from bulk fl id attach to the e isting biofilm fluid attach to the existing biofilm – Can result in species displacement
- 19. Attachment and Coaggregation Attachmentand Coaggregation • Coaggregation – is the attachment of distinct gg g bacteria via specific molecules – Single cells in bulk fluid specifically recognize and adhere to genetically distinct cells in developing adhere to genetically distinct cells in developing biofilm – Prior coaggregation in suspension followed by subsequent adhesion to existing biofilm subsequent adhesion to existing biofilm • Multi-species biofilms are a functional consortium that often posses a combined p metabolic activity that is greater than the individual component species
- 20. Step 7: Re-entrainment Step7: Re entrainment • Cells detach from the surface and return to the bulk fluid and planktonic form of growth • Detachment can occur E i – Erosion – Sloughing – Human intervention Human intervention – Predatory grazing – Abrasion – Starvation • Detachment can be an active or passive process leading to further survival or colonization leading to further survival or colonization
- 21. Biofilm degradation Biofilm degradation •Microorganisms require energy to “maintain” Microorganisms require energy to maintain existing structures and processes • Important process during starvation survival p p g • Can occur from endogenous decay and death – Endogenous decay – the depletion of intracellular constituents that occurs when cells have insufficient exogenous supplies • i e Starvation i.e. Starvation – Death – the permanent loss of a cell’s reproductive and metabolic activity
- 22. Cell-cell signaling Cell cellsignaling “Quorum” – the minimal number of people who must be present for a decision to be binding Autoinduction
- 23. Quorum Sensing –Genetic Regulation Quorum Sensing Genetic Regulation
- 24.
- 25. Biofilm Communities Biofilm Communities •Multispecies communities Multispecies communities • Described in terms of O i – Organisms – Structure – Interactions – Coordination
- 26. Biofilm Advantages Biofilm Advantages •Enhanced scavenging of nutrient from bulk liquid g g q and surface • Physiological alterations E h d h – Enhanced growth rates – Higher DNA synthesis and RNA turnover rates – Enhanced resistance Enhanced resistance – Enhanced virulence – Greater local diversity • Physical protection and stabilization • High densities – provide framework for coordinated and socialized behavior coordinated and socialized behavior
- 27.