How Do Biofilms Form?

Overview of Biofilm Development

Biofilm formation generally follows five stages:

1. Attachment

Biofilm formation begins when free-floating (planktonic) microorganisms come into contact with a surface. Initially, the interaction is reversible and driven by physical forces (e.g. van der Waals, electrostatic, hydrophobic interactions).
If environmental conditions are favorable, bacteria irreversibly attach using appendages such as pili, fimbriae, or flagella, and begin secreting adhesive substances.
Surface types: natural (rocks, teeth), industrial (pipes), or biological (tissues, medical implants)
Timeframe: minutes to hours
If environmental conditions are favorable, microbes proceed to irreversible attachment.

2. Microcolony Formation
Once cells are irreversibly attached, they begin to proliferate and form microcolonies, small clusters of cells tightly bound to the surface. Cells initiate the production of extracellular polymeric substances (EPS)—a matrix composed of polysaccharides, proteins, lipids, and extracellular DNA (eDNA).
EPS provides mechanical stability and traps nutrients.
Cells begin to coordinate via quorum sensing, a chemical communication process
Microcolonies serve as the foundation for the developing biofilm.

3. Early Biofilm
Microcolonies transition into an early-stage biofilm, characterized by more extensive EPS production and the recruitment of additional cells. The structure becomes increasingly three-dimensional, with developing channels that facilitate fluid and nutrient movement.
Gene expression changes to enhance biofilm-specific traits (e.g., stress tolerance, antibiotic resistance)
Microenvironmental gradients of oxygen and nutrients emerge within the developing layers

This stage marks the establishment of a cooperative microbial community.

4. Mature Biofilm

In the mature stage, the biofilm becomes a complex and heterogeneous structure. It often forms towers, mushroom-like shapes, or thick films with interconnected water channels for waste and nutrient transport.
Multispecies communities are common
Cells display increased resistance to antibiotics, immune responses, and environmental stress
Metabolic cooperation and differentiation between cell populations occur
This highly organized community can persist for long periods and is typically the most resilient form of a biofilm.

5. Dispersion
Eventually, environmental signals (e.g., nutrient limitation, shear stress, changes in pH) trigger a portion of the biofilm to disperse. Cells return to a planktonic state, allowing colonization of new surfaces.
Dispersion can be active (enzymes breaking down EPS) or passive (mechanical disruption)
Facilitates biofilm spread across environments or tissues
This phase is critical for the lifecycle and adaptability of biofilm-forming organisms.

Learn more in our case study: Eliminating Microbiological Contamination in Ozone Fruit Wash Water

Real-World Examples of Biofilm Formation

Biofilms are not limited to laboratories or hospitals—they occur in a wide range of real-world environments, often with serious implications for performance, safety, and health.

Aquaculture

Example
Biofilms develop on fish tanks, nets, and recirculating systems, harboring pathogens like Aeromonas or Vibrio that can infect fish stock and reduce water quality.

Impact
Increased mortality, poor fish health, reduced feed conversion efficiency.

Agriculture

Example

Biofilms form inside drip irrigation lines and emitters, especially when using nutrient-rich or recycled water.

Impact

Clogging of irrigation systems, uneven water distribution, and reduced crop yields.Clogging of irrigation systems, uneven water distribution, and reduced crop yields.

Animal Nurseries / Livestock

Example
Biofilms establish on feeding equipment, water lines, and floor surfaces in pens or barns.

Impact:
Persistent reservoirs of pathogens such as Salmonella, E. coli, and Listeria, increasing disease risk in young animals.

Food and Beverage Processing

Example
Biofilms commonly occur on processing surfaces, pipes, and conveyor belts, especially in dairies, breweries, and meat processing plants

Impact
Cross-contamination of food, reduced shelf life, and major hygiene compliance risks.

Sports Turf Management

Example
Biofilms can build up in subsurface drainage and irrigation systems of golf courses and sports fields.

Impact
Water flow restrictions, turf disease promotion, and localized flooding.

Lakes and Ponds

Example
Naturally occurring biofilms form on rocks, sediment, and submerged structures, but can become problematic with nutrient loading (eutrophication).

Impact
Fueling harmful algal blooms, lowering oxygen levels, and affecting biodiversity.

Next in the Series

“Why Are Biofilms Dangerous?”
Explore how biofilms evade immune responses, resist antibiotics, and cause persistent infections in medical and environmental settings.