Biofilmbasics - PDF document

OEST 740011508 Biofilmbasics Biofilm basics • Biofilmsarenowbelievedtobetheprimarymode Biofilms are now believed to be the primary mode of existence for bacteria in aqueous environments.1,000 –10,000x greater populations than planktonicDefined as a consortium of microorganisms tllltiltdbthihbiti ex t race

ll u l ar ma t er i a l secre t e d b y th e i n h a biti organisms. • Theestablishmentmaintenanceandexistenceof • The establishment , maintenance and existence of biofilm communities are highly complex, socially organizedprocesses. organized processes. Biofilmbiology Biofilm biology • Investigates

theconsequencesoftheclose Investigates the consequences of the close association of microorganisms at interfaces. iil •Common pr i nc i pa l s –Attachment Cdhi – C oa dh es i Regulation of biofilm phenotype – Biofilmarchitecture Biofilm architecture Interfaces Interfaces •Solid:Li q ui d q Gas:Soli

d(often exposed to liquids) – Lichen, trickling filters, myxobacterialswarms Neuston penicillinproducedbyfungalfermentation – Neuston , penicillin produced by fungal fermentation •Liquid:Liquid – H y drocarbon oxidizin g biofilm at oil:waterinterfaces yg Solid:Solid(periodically exposed to liquid)Endolith

otrophiccommunities Biofilmimpact Biofilm impact • Thedevelopmentofbiofilmshasimportant The development of biofilms has important impacts – Bacterial p ro p erties pp VirulenceSettlement and metamorphosis of higher organisms organisms The physical and chemical structure of the surfaces y are establishe d y B

iofilmImpact Biofilm Impact •Thus , the y are p otentiall y relevant to a wide ,ypy processes in aqueous environments – Biology–Engineering – Medical –Dental BiofilmComposition Biofilm Composition Ct %Ttl Diti Oii C omponen t % T o t a l D escr i p ti on O r i g i Water Up to 95%Characteristics dete

rminedbydissolved determined by dissolved Microbial cells2-5 % Polsaccharides 1 2% Netral and polanionic ; Etracelllar Pol y saccharides 1 - 2 % Ne u tral and pol y anionic ; homo and heteropolysaccharides E x tracell u lar Proteins - 2% Enzymes Extracellularand Proteins 2% Enzymes Extracellular and DNA and RNA1-2%Celllys

is Ions ? Boundorfree Ions ? Bound or free EPS present in biofilms is thought to closely resemblethecorrespondingpolymerssynthesized resemble the corresponding polymers synthesized by planktonic cells. – Carbon (intra and extra-cellular)Carbon:Limitingnutrient – Varyinproportionsofvariouscomponents – Vary

in proportions of various components Some are neutral macromolecules, but majority p ol y anioninic py �Uronic acids (D-glucuronicD-galacuronic= D- – Ketal - linked pyruvate Ketal - linked pyruvate Exopolysaccharides Exopolysaccharides Ver y few are p ol y cationic y py –S. epidermidis•In nature, ex

ist in ordered configurations of low temperaturesalineconditions temperature , saline conditions Very long, thin molecular chainsMolecular mass 0.5-2.0 x 10 Aiif • A ssoc i at i on o f Electrostatic and hydrogen bonding are dominate forces Providebacteriawithbackbonestructure,measureof Provide bacteria with backbone s

tructure, measure of homeostasis, primitive circulatory system and a large Formation•Biofilm formation begins with a transition of bacteria from the planktonic (free swimming) form to its geneticallydistinctattachedform genetically distinct attached form .•The genetic transition occurs across the life cycle of th

e Cdiii – C on di t i on i ng–Contact – Adsor p tion p –Growth–Production of extracellularproducts extracellular products –Attachment–Re-entrainment Photo:CEB:MSU - Bozeman Photo: CEB : MSU - Bozeman Step1:Conditioning Step 1: Conditioning • Acleansurfaceisimmediatelycoveredwitha

A clean surface is immediately covered with a conditioning film of organic molecules and macromolecules macromolecules Transport of molecules and small particles is rapidandasaresultadsorptionofconditioning rapid and as a result adsorption of conditioning film occurs instantaneously Thfhdiiifill • T

h e presence o f t h e con di t i on i n g fil m a l the characteristics of the substratum. Effect Substrate Substrate hydrophobicity decreases negative charge increase or decrease Ciilf • C r i t i ca l sur f tensions increase or decrease decrease Step 2: Contact•Bacteria in fluid contact the substrate via mass trans

port mechanisms•Strongly influenced by mixing in the bulk flui d Related to flow regime p ort p –Sedimentation–Motility – Molecular diffusionTurbulent flow transport (larger particles) – Diffusivetransport – Diffusive transport Bacteria penetrate the viscous sublayer(~1 cm) via eddy diffusion • B

acteriaactielmigratethroghthediffsie sblaer • Bacteria acti v el y migrate thro u gh the diff u si v e s u bla y er using pili(~1 mm) Step3:Absorption Step 3: Absorption • Atthesubstratethecellsabsorbreversiblyor At the substrate the cells absorb reversibly or irreversibly – Primary(early)

colonization Primary (early) colonization Adsorption –accumulation of cells directly on surface fb o f su b Desorption –re-entrainment of cells into the bulk fluid • Complexprocess • Complex process Adsorption Adsorption • Initialadsorptionoccursthroughlong - range(100s Initial adsorption occurs

through long range (100s nm), weak interactions with low specificity – Electrostaticorvan der Waalsforces Electrostatic or van der Waals forces •Irreversible adsorption is short-range (5nm), highlyspecificinteraction highly specific interaction –Dipole, ionic, hydrogen bonding, hydrophobic interaction

s, etc.–Can take place by secretion of EPS or fibrillar Step4:Growth Step 4: Growth • Thenumberofirreversiblyadsorbedcells The number of irreversibly adsorbed cells increase due to replication Limitedbyphysiologicalprocesses – Limited by physiological processes Concentration of rate-limiting nutrient

important Affixed cells transition from planktonic form Processes controlled by gene encoding for the production of products Ste p 6: Attachment p Secondary (late) colonizing cells from bulk flidattachtotheeistingbiofilm fl u id attach to the e x isting biofilm –Can result in species displacement AttachmentandCoaggr

egation Attachment and Coaggregation •Coa gg re g ation – is the attachment of distinct ggg b acteria via specific molecules adheretogeneticallydistinctcellsindeveloping adhere to genetically distinct cells in developing Prior coaggregationin suspension followed by subsequentadhesiontoexistingbiofilm subseq

uent adhesion to existing biofilm •Multi-species biofilms are a functional consortium that often p osses a combined p metabolic activity that is greater than the Step7:Re - entrainment Step 7: Re entrainment Cells detach from the surface and return to the b ulk fluid and planktonic form of growth Ei – E ros

i on–Sloughing – Humanintervention Human intervention –Predatory grazing–Abrasion – Detachment can be an active or passive process leadingtofurthersurvivalorcolonization leading to further survival or colonization Biofilmdegradation Biofilm degradation • Microorganismsrequireenergyto “

maintain ” Microorganisms require energy to maintain existing structures and processes•Im p ortant p rocess durin g starvation survival ppg Can occur from endogenous decay and deathEndogenous decay –the depletion of intracellular constituents that occurs when cells have insufficient ieStarvation i . e . S

tarvation Death –the permanent loss of a cell’s reproductive and Cell - cellsignaling Cell cell signaling “Quorum” –the minimal number of people who must be present for a decision to be Autoinduction QuorumSensing – GeneticRegulation Quorum Sensing Genetic Regulation BiofilmFormation Biofilm Fo

rmation BiofilmCommunities Biofilm Communities • Multispeciescommunities Multispecies communities •Described in terms of Oi – O rgan i sms–Structure – Interactions–Coordination BiofilmAdvantages Biofilm Advantages •Enhanced scaven g in g of nutrient from bulk li q uid ggq and surface•Ph

ysiological alterations Ehdh – E n h ance d growt h Higher DNA synthesis and RNA turnover rates – Enhancedresistance Enhanced resistance Greater local diversityPhysical protection and stabilizationHigh densities –provide framework for coordinatedandsocializedbehavior coordinated and socialized behavior Questio