Biofilms Final

8/8/2019 Biofilms Final

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Biologically active matrix

of cells and extracellularproducts attached to a

solid surface

Microbial community

forming a slimy layer on

a surface


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Assemblage oforganisms that can beof different or same

species held togetherby extracellular

polymeric substancesor EPS which allows

them to developcomplex threedimensional, resilient,attached communities.


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Develop in all kinds of surfaces where

there is moisture and nutrients.

Although bacteria require aqueous

conditions for growth, they will adhere toany surface be it inorganic, living or

dead materials, or organic remains.


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Inert surfaces Community water

system pipes

Sulfide tailings andacid mine drainage

system

Industrial wastetreatment machines


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Living cell

surfaces

Plant root system

Ruminant digestivetract

Biliary system

Urinary tract

Teeth


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Able to exploitessential nutrientswhich accumulate inthe form of ions andmacromolecules atthe surface-waterinterface giving thema distinct ecologicaladvantage in an

otherwise nutritionallyunfavorableenvironment(Brown et al., 1981)


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Some examples are:

Staphylococcus aureus - catheters andsurgical implants

Streptococcus mutans - dental plaques

Candida albicans catheters, contactlenses

Coloechaete scutata, Choleochaete soluta- colony proliferation on the surface ofpolyethylene (plastics)


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Pseudomonasaeruginosa is acommon "pioneerbacteria whichcan adhere tostainless steel, evento electropolishedsurfaces, within 30seconds ofexposure.


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Heterogeneous structure which includes cellclusters, void spaces, water channels, endslime streamers that are affected by flow of

the fluid surrounding the biofilm


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Biofilm formation is affected by:

Surface material

Smoothness Flow velocity

Nutrient availability


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1. Surface conditioning

2. Adhesion of pioneer bacteria

3. Slime formation

4. Secondary colonizer

5. Fully functioning biofilm


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First, organic

molecules adhere

to the surfaceand they

neutralize the

surface charge

which may repelapproaching

bacteria.


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Planktonic (free-floating) bacteria firstattach themselves by

electrostaticattraction andphysical forces. Someof these cells will

permanently adhereto the surface withtheir extracellularorganic matrix.


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Extracellular polymersconsisting of charged andneutral polysaccharidegroups cement the cell and

act as an ion exchangesystem for trapping and

concentrating trace nutrients

Accumulation of nutrientspromotes reproduction of

pioneer cells. The daughtercells then produce their ownexopolymers, greatlyincreasing the volume of ion

exchange surface.


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The exopolymer websnares other types ofmicrobial cells throughphysical restraint andelectrostaticinteraction. Thesesecondary colonizersmetabolize wastes from

the primary colonizersas well as producetheir own waste whichother cells then use.


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Microbe-microbeinteraction Production of

metabolites byprimary colonizersmay promote orinhibit secondarycolonizers

The thicker thebiofilm, the higherthe occurrence ofanaerobiosis is


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Microbe-surface interaction

The rate of initial biofilm formation bybacterial adhesion is to a degreedependent on the chemical nature of thesurface

Type of bonding that exists between thebacteria and the substratum must be takeninto consideration.


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The process of communication of

bacteria to respond to local cell density

Regulates the secretion of stickyextracellular slime

Some species use quorum sensing to turn onslime production at high cell density; while

some turn it off.

Synchronize the expression of specialized

gene systems


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Less susceptible to antimicrobial agents

The matrix itself protects the cells from

coming into contact with the antimicrobialeffect of the agent.

e.g.

If the antimicrobial agents mode of action is

oxidizing,


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1: individual cells populate the surface. 2: extracellular polymeric substance

(EPS) is produced and attachment becomes irreversible.3 & 4: biofilm architecture develops and matures.

5: single cells are released from the biofilm.


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Release of bacteria from a biofilm may

be due to production of unattached

daughter cells through attached cellreplication. Other factors that promote

detachment are bulk fluid flow, lack of

oxygen, accumulation of toxic waste

products, biological grazing andpredator harvesting.


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Increased resistance toantibiotic andantibacterial substances

Resistance towards

disinfecting chlorines Metal corrosion due to

sulfate-reducingbacteria

Dental decay Food and water

contamination due tocolonization of pipes


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Used in waste watertreatment fordegradation ofsoluble organic or

nitrogenous waste Stabilize soil, either

by acting ascementing agent orflocculating soil

particles therebyimproving aerationand waterpercolation


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Ettinger, M. Advanced Healing.Com Journal. Retrieved 2

September 2010 fromhttp://www.advancedhealing.com/blog/2009/09/25/dr-

ettingers-biofilm-protocol-for-lyme-and-gut-pathogens/

Korber, D.R., J.R. Lawrence, H.M. Lappin-Scott, and J.W. Costerton.1995. Growth of microorganisms on surfaces. In: H.M. Lappin-Scott and J.W. Costerton (ed). Microbial biofilms. pp. 15-45.

Cambridge University Press, New York.

Lappin-Scott, H.M. and J.W. Costerton. 1995. Microbial biofilms. pp.

15-45. Cambridge University Press, New York.

Marsh, P.D. 1995. Dental plaque. In: H.M. Lappin-Scott and J.W.Costerton (ed). Microbial biofilms. pp. 15-45.Cambridge

University Press, New York.

McArthur, J.V. 2006. Microbial ecology: an evolutionary approach.pp. 257-261. Elsevier Inc., Burlington, MA, USA.

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Biofilms Final