The BIOFILM concept

University of Barcelona team/Oliver-Rodés

Miquel SalgotAntonio BorrellAlex Mezquida

BIOFILM = Microbial community on a surface

BIOFILM

Fixed bacteria (sessile)Surface able to be

colonized (rough)

The presence of nutrients conditions the change from reversible adhesion to not-reversible adhesion phases

Free swimming bacteria (in the planktonic phase)

BIOFILM

Fixed bacteria (sessile)

Plus dirt, other microorganisms and exopolysaccharides

(“gum” formed by the bacteria) = BIOFILM

In a BIOFILM microorganisms are protected from externalattacks

• An external barrier of polysaccharides is formed (protection,cohesion)

• Big molecules cannot enter the biofilm (e.g. antibiotics,disinfectants)

• Bacteria are more resistant in biofilms (are stressed)

• Transfer of resistance among bacteria (e.g. to antibiotic,disinfectants) due to the proximity conditions (side by side)

Nutrients in water are fixed by the biofilm (better growth)

Microscopic organisms, components of Biofilms

• Pseudomonas fragi over inox steel, after 24h at 23⁰C

With exopolysaccharides microorganisms anchorage to the surface starts

• P fragi (PS) over inox steel, after 10 days at 7⁰C

Accumulation of extracellular material (exopolysaccharides) entrapping dirt

• Joint development of P fragiand embedded Listeria monocitogenes (reach the site with the dirtyness) over inoxsteel, after 7 days at 7⁰C

Ps fragi is mainly forming the biofilm, Listeria is embedded with the dirt not decomposed

Biofilm formed by Ps aeruginosa,over nitrilic rubber, after 64 hoursincubation

Biofilm formed by Ps aeruginosa, overinox steel surface, after 93 hoursincubation

BIOFILM ELIMINATION

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 mediafor new development of microorganisms

• Layers of material remain which impede the access ofdisinfectants to the target microorganisms

If surfaces are not disinfected after cleaning, an excessivenumber of organisms remain on the surfaces; they willeasily multiply again

Biofilm elimination / Several possibilities

- Classical way as indicated: Detergents + Rinse + Disinfection + Rinse

- Combine several disinfectants (Chlorine derivatives, Peracetic acid, Ozonatedwater…) instead of a single one

- Hard ways: e.g. steam in the pipes

Last operation

Rinse afterwards and do not use the first water issuing from the system (calculate the water that can remain inside the pipes and at least duplicate it – discard this water)

BIOFILM IMPORTANCE

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

THIS IS NOT THE CASE FOR BOTTLING WATER SYSTEMS