Biofilms are structured communities of microorganisms that attach to surfaces and to each other. These cells become encased in a self‑produced matrix of extracellular polymeric substances, which glues them together and anchors them to the interface. The matrix traps nutrients and waste, creating a microenvironment distinct from the surrounding fluid.
Explanation
Within a biofilm, microbial cells secrete a slimy extracellular matrix composed mainly of polysaccharides, proteins, lipids and extracellular DNA. This matrix forms a gel-like scaffold that binds cells, stabilises the community and protects inhabitants from desiccation, ultraviolet light, disinfectants and antibiotics. Biofilm development begins when planktonic cells adhere reversibly to a surface; they then proliferate, excrete matrix and recruit additional organisms. Channels form within the structure to allow water and nutrients to circulate. Metabolic gradients arise because outer layers consume substrates and oxygen first, so deeper cells grow slowly or enter dormant states. These physiological differences, along with reduced penetration of antimicrobials through the matrix, make biofilm-associated organisms notoriously hard to eradicate. Biofilms are not limited to bacteria; archaea and microscopic eukaryotes can join these consortia.
Formation and Impact
Biofilms occur wherever microbes encounter moisture and surfaces. In nature they coat stones and plant roots in streams, forming the basis of aquatic food webs. In humans they manifest as dental plaque, the slimy film on teeth that leads to caries if not removed. They are also responsible for persistent infections on medical devices such as catheters, prosthetic joints and heart valves. The matrix protects bacteria such as Staphylococcus aureus or Pseudomonas aeruginosa from host defences and antibiotics, resulting in chronic, relapsing infections. Biofilms form in industrial settings on ship hulls and pipes, causing corrosion and reduced flow. They are not exclusively harmful: biofilms are harnessed in wastewater treatment, bioreactors and bioremediation to degrade pollutants efficiently. Understanding biofilm formation and control is therefore vital across dentistry, medicine, environmental engineering and industry.
Biofilms exemplify the cooperative and adaptive behaviour of microbes. Their resilience stems from the collective action of cells and their extracellular matrix. Strategies to prevent biofilm formation or to disrupt existing communities are important for controlling infections and maintaining infrastructure, while exploiting beneficial biofilms continues to be an area of active research.
Related Terms: Bacteria, Extracellular matrix, Quorum sensing, Biofilm formation, Antibiotic resistance