Imagine a city constructed by microbes, a lively, slimy metropolis where bacteria and other microorganisms bond together, protect themselves from danger, and interact like neighbors1. That’s what a biofilm is. You’ve likely come across one if you’ve ever felt the slick coating on river rocks or noticed the plaque on your teeth. However, these microbial cities are much more intricate and resilient than they seem at first glance.
How biofilms begin: the art of sticking around
It all begins with a single microbe floating through water or fluid, on the lookout for a place to settle. When it comes across a suitable surface— a medical device, a pipe, a tooth, or even a piece of microplastic, it attaches itself loosely initially, relying on weak forces like van der Waals attractions or hydrophobic effects2. If it deems the spot favorable, it anchors itself more firmly, utilizing adhesive structures like pili or fimbriae. At this stage, the attachment becomes irreversible, and the microbe officially enters biofilm mode.
It’s fascinating how the composition of a biofilm changes depending on the surface and the surrounding environment. For example, biofilms found on microplastics typically host a diverse range of environmental bacteria, including some that carry resistance genes, whereas biofilms on nutrient-dense surfaces are often mainly made up of conventional pathogens.
Building the matrix: microbial engineering at its finest
Once a few microbes have taken root, they begin to multiply and secrete viscous extracellular polymeric substances, called exopolysaccharides (EPS)3. This matrix is a blend of polysaccharides, proteins, DNA, and lipids, a type of microbial adhesive that binds the community together and shields it from external threats. The EPS serves more than just adhesion; it forms a three-dimensional structure with water channels, akin to plumbing, to transport nutrients in and expel waste out. As the biofilm develops, it transforms into a vibrant, three-dimensional city, with various species of microbes cohabiting, sharing resources, and communicating through chemical signals referred to as quorum sensing.
Biofilms: masters of survival, resistance, and evolution
Biofilms represent more than just a collaboration of microbes, they function as survival machines. When microbes inhabit a biofilm, they gain significant resilience1. The EPS matrix serves as a protective barrier, making it challenging for antibiotics, disinfectants, or even the immune system to penetrate and reach the cells within. This characteristic is what makes biofilms a significant concern in hospitals, where they can establish themselves on catheters, implants, and wounds, resulting in persistent infections that are extremely hard to manage. However, the issues extend beyond that. Within a biofilm, bacteria can exchange genetic material— including genes that confer antibiotic resistance, at a much higher frequency than when they exist independently4.
Biofilms as reservoirs for antimicrobial resistance
The compact, secured environment of a biofilm provides an ideal backdrop for bacteria to share and gather resistance genes via HGT5. Biofilms found on medical devices, hospital surfaces, wastewater pipes, and even microplastics can turn into hotspots for the emergence and proliferation of multidrug-resistant bacteria. In a world where infections can traverse continents within hours, biofilms could potentially trigger the next pandemic of untreatable infections.
Biofilms and cancer: An underappreciated connection
Chronic biofilm infections do not only result in persistent wounds or implant failures, they are increasingly associated with cancer6. In organs such as the colon, ongoing inflammation driven by biofilms can foster an environment conducive to the development and survival of cancerous cells7. Genetic alterations in oncogenes and tumor suppressor genes lead to uncontrolled cell proliferation while epigenetic modifications contribute to cancer cell plasticity and adaptability. The immune system’s ongoing struggle against biofilm communities can result in DNA damage and alterations in tissue that pave the way for cancer8. Additionally, tumor microenvironment interactions promote immune evasion, and metabolic reprogramming allows cancer cells to adapt their energy production to support rapid growth and survival under adverse conditions.
Anti-biofilm strategies
Anti-biofilm strategies are critical in combating persistent infections. According to recent research, effective approaches include the use of agents that disrupt the biofilm matrix, such as enzymes (DNases and proteases) and surfactants, which help break down the protective EPS layer9. Additionally, novel antimicrobial compounds, nanoparticles, and bacteriophage therapy are being explored for their ability to penetrate and eradicate biofilms. Combining traditional antibiotics with these agents often enhances treatment efficacy. Other promising strategies involve the development of surface coatings that prevent biofilm formation on medical devices, as well as the use of quorum sensing inhibitors to block the communication signals bacteria use to organize biofilm growth. Collectively, these multifaceted approaches represent a significant advancement in the prevention and management of biofilm-associated infections.
The bright side: beneficial biofilms
It’s not all doom and gloom. Biofilms can be used in beneficial ways as well. For instance, in our own bodies, beneficial bacteria in the gut microbiome form protective biofilms, playing a vital role in digestion and immune health. In the process of bioremediation, specially engineered biofilms break down pollutants found in contaminated soil and water, helping to clean up oil spills and detoxify industrial waste10. In wastewater treatment plants, biofilms are essential for decomposing organic materials and removing harmful substances, which makes our water safer for drinking and for reintroducing into the environment. When handled correctly, these microbial communities act as powerful partners in promoting environmental protection and sustainability.
The cycle continues: dispersal and new beginnings
Eventually, certain microbes break away from the biofilm, either individually or in clusters, and drift off to settle on new surfaces. This dispersal enables biofilms to spread and restart the process in locations where conditions are suitable.
The hidden menace — and opportunity
Thus, biofilms are not merely slimy layers, they are well-organized, resilient communities that enable microbes to thrive in harsh conditions, evade antibiotics, and exchange survival tactics. They are pivotal in the dissemination of antimicrobial resistance, can play a role in cancer progression, and can adapt to almost any surface. Nonetheless, with appropriate strategies, they can also be utilized for environmental advantages. Whether they are obstructing pipes, leading to ongoing infections, or assisting in pollution remediation, biofilms act as a strong reminder that microbes, when collaborating, are much more than merely the total of their separate parts.