Biofilm Aquasin EN

1. BIOFILMS

2. BIOFILM
Biofilms:
Microorganisms’ populations which multiply when adhered to a surface and
embedded usually in an extracellular matrix (mainly exopolysaccharides)
Bacteria in the planktonic
phase (free “swimming”)
Fixed bacteria
Surface able to be colonized (sessile)
(rough)
(The presence of nutrients
conditions the change from
reversible adhesion to not-reversible
adhesion phases)

4. BIOFILM’s FUNCTIONS
To protect microorganisms from external attacks
•There is a barrier effect created by the polysaccharides, limiting the diffusion of foreign molecules. Directly, is only effective against big molecules (e.g. antibiotics) but increases the enzymatic effect even with small molecules like hydrogen
•Ionic effect of the usually negatively charged polysaccharides, which fix the positively charged molecules reaching the biofilm, like aminoglycosylated antibiotics or quaternary ammonia
•Enzymatic effect. Immobilization of several enzymes, like b-lactamase or peroxidase in the extracellular matrix
•Chemical effect. Reaction of the extracellular polysaccharides with several disinfectant molecules, like hypochlorite
•Physiological effect. In the biofilm suboptimal conditions are created, representing a stress condition, where bacteria use to be more resistant than in optimal conditions
•Genetic effect. Due to existing proximity conditions and relationships, gene transfer causing increased resistance to several agents (e.g. antibiotics) can be described usually Nutrients are fixed by the biofilm

5. BIOFILM FORMATION
• Pseudomonas fragi over
inox steel, after 24h at 23ºC
The presence of
exopolysaccharides
branches can be observed
This initiates the
microorganisms anchorage
• Ps fragi (PS) over inox
steel, after 10 days at 7ºC
It is to note the
accumulation of
extracellular material
(exopolysaccharides)
entrapping dirt
• Joint development of Ps fragi
and Listeria monocitogenes over
inox steel, after 7 days at 7ºC
One of the microorganisms (Ps
fragi) is mainly forming the
biofilm, where the other
organism is embedded with the
dirt not decomposed

6. BIOFILM
Biofilm formed by Ps aeruginosa, over a
nitrilic rubber, after 64 hours incubation
Biofilm formed by Ps aeruginosa, over a inox
steel surface, after 93 hours incubation

7. THEORETICAL PROCESS OF BIOFILM FORMATION

8. BIOFILM ELIMINATION
If surfaces are not being cleaned before disinfection:
• The real focuses of pollution are not being eliminated
• A basis of substrate remains which is a culture media for new development of
microorganisms
• Layers of material remain which impede the access of disinfectants to the target
microorganisms
If surfaces are not disinfected after cleaning, an excessive number of organisms remain on the
surfaces; they will easily multiply again

9. BIOFILM IMPORTANCE
Nevertheless, Biofilms are important in nature and water treatment, since (e.g.)
•Are the basis for a number of water treatments
•Constitute the major system of self-treatment in water bodies