July 6, 2025

What is Biofilm

Biofilm of Desulfovibrio Desulfuricans

Biofilms are structured communities of microorganisms that attach to surfaces and embed themselves in a self-produced matrix of extracellular polymeric substances (EPS). These complex microbial ecosystems are remarkably resilient and are found in a wide range of natural, industrial, and clinical environments.

1. Defining Biofilm

At its core, a biofilm is:

“A sessile microbial community characterized by cells that are irreversibly attached to a surface or to each other, embedded in a matrix of EPS, and exhibiting an altered phenotype with respect to growth rate and gene transcription.”

— Costerton et al., 1995

The EPS matrix—primarily composed of polysaccharides, proteins, and nucleic acids—acts as a protective barrier and structural scaffold, making biofilms highly resistant to external stresses.

2. Microbial Composition

Biofilms are not single-species colonies. In most cases, they are multi-species consortia that include:

  • Bacteria (e.g., Pseudomonas aeruginosa, Staphylococcus aureus)

  • Fungi (e.g., Candida albicans)

  • Algae

  • Protozoa

These organisms communicate using chemical signaling (quorum sensing) and coordinate their behavior for survival and adaptation.

3. The Biofilm Life Cycle

Biofilm formation is a dynamic process that occurs in several stages:

  1. Attachment: Free-floating (planktonic) microbes adhere weakly to a surface.

  2. Microcolony: Cells produce EPS and anchor firmly to the surface.

  3. Early biofilm: Beginning growth stage for a mature colony

  4. Maturation: The biofilm grows in complexity and thickness, forming channels for nutrient and waste exchange.

  5. Dispersion: Cells or clusters detach and return to the planktonic state to colonize new surfaces.

Each stage is regulated by environmental conditions and microbial communication.

4. Where Biofilm Forms

Biofilms can form on virtually any surface that is:

  • Moist

  • Nutrient-rich

  • Exposed over time

Common examples:

  • Teeth (dental plaque)

  • Medical implants (catheters, prosthetics)

  • Industrial pipelines

  • Water filtration membranes

  • Natural surfaces (rocks in rivers, plant roots)

5. Why Biofilms Matter

Biofilms are more than just a nuisance—they have significant impacts across sectors:

Medicine
Biofilm-associated infections are notoriously hard to treat and often recur.

Industry
Biofilms cause corrosion, clogging, and contamination in water systems and manufacturing equipment.

Agriculture
They affect irrigation efficiency and plant health.

Environment
They influence nutrient cycling and pollutant breakdown in aquatic systems.

Their resistance to antibiotics, disinfectants, and physical stress makes them especially problematic.

Key Facts
  • Biofilms can be up to 1,000 times more resistant to antibiotics than planktonic bacteria.

  • The EPS matrix can make up 50–90% of the biofilm’s total organic carbon.

  • Biofilms are responsible for ~80% of chronic infections, according to the NIH.

Coming Next

In the next article:
“How Do Biofilms Form?” — A closer look at the environmental triggers, microbial signaling, and step-by-step development of biofilm communities.

FAQ

Is biofilm the same as mold or algae?

Not exactly. Mold and algae can form biofilms, but a biofilm refers more broadly to any community of microorganisms (bacteria, fungi, algae, etc.) living together on a surface in a self-produced matrix. So, while mold or algae can be part of a biofilm, not all biofilms are mold or algae.

Is biofilm the same as mold or algae?

Not exactly. Mold and algae can form biofilms, but a biofilm refers more broadly to any community of microorganisms (bacteria, fungi, algae, etc.) living together on a surface in a self-produced matrix. So, while mold or algae can be part of a biofilm, not all biofilms are mold or algae.

Is biofilm the same as mold or algae?

Not exactly. Mold and algae can form biofilms, but a biofilm refers more broadly to any community of microorganisms (bacteria, fungi, algae, etc.) living together on a surface in a self-produced matrix. So, while mold or algae can be part of a biofilm, not all biofilms are mold or algae.

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References