In this lesson, you’ll learn what bacterial biofilms are and how they form. Learn about the positive and negative sides of biofilms and where you can find them growing.
What Are Biofilms?
Have you ever picked up a rock from a nearby stream and wondered why it’s slimy on the surface? That slimy layer is actually a group of microorganisms, collectively called a biofilm. A biofilm is a community of bacteria that attach to a surface by excreting a sticky, sugary substance that encompasses the bacteria in a matrix. This might be the first time you’ve heard the term biofilm, but they’re actually all around us, in streams, in drains, in fish tanks, even on our teeth.
A biofilm can be composed of a single species or a conglomerate of species. In many cases, biofilms are only bacteria, but they can also include other living things, such as fungi and algae, creating a microbial stew of sorts. Biofilms are complex systems that are sometimes compared to multicellular organisms.
How Are Biofilms Formed?
Biofilm formation begins with planktonic, or free-swimming, bacteria, which land on a surface. Bacteria can attach to a variety of surfaces, from woods, metals, and plastics to living tissues and stagnant water. The cells are able to attach to the surface by excreting a sugary molecule that holds the cells together and attaches them to the surface. This sugary substance is called extracellular polymeric substance, or EPS, and has a strand-like structure that allows it to bind to the surface and to other cells, creating a matrix.This matrix of cells and strands can be quite complex: the cells may even share genetic material and have organized structure.
A biofilm can be as thin as a single cell or as thick as several inches, depending on conditions in the environment. As a biofilm grows and develops, it thickens and becomes mature. If there is sufficient water and nutrients, the biofilm will develop until small portions detach and float to another surface and colonize.
Biofilms that Affect Humans
Biofilms can take a variety of forms – from the plaque on your teeth to slime buildup in your sink. These microscopic organisms can cause billions of dollars of damage each year in industrial, medical, and domestic settings by clogging equipment and harboring infectious bacteria.One type of biofilm is dental plaque, which attaches to your teeth and causes cavities and gum disease.
Over 500 species of bacteria have been implicated in the formation of dental plaque. Oral appliances, such as dentures and mouth-guards, are a prime location for biofilm growth. In medical equipment, biofilms can decrease the effectiveness of sterilization procedures, resulting in increased medical infections.
Biofilms have been associated with infection in contact lenses, catheters, heart valves, pacemakers, and artificial joints.
Recently, there has been an increased research effort to more fully understand biofilms and their mechanism of attachment and survival. Research has shown that the formation of biofilms can make bacteria less susceptible to antimicrobial products. The thick, slimy layer can protect bacteria in the middle of the biofilm from the effects of an antimicrobial.
This is especially concerning where human health may be affected (for example, on medical devices or in food handling areas). The survival power of bacteria in a biofilm is much higher than that of planktonic bacteria.
While slimy bacterial growth may seem like a negative, there are some surprising benefits of biofilms.
On the plus side, biofilms can be used to filter and clean wastewater. They can also reduce hazardous waste through the process of bioremediation, where bacteria break down waste into non-hazardous products. Researchers have also discovered that our large intestines support a biofilm of beneficial bacteria that help us digest our food and may help us form a healthy immune system.
A biofilm can be made up of many different species of bacteria and may even include algae and fungi.
They start with planktonic bacteria cells attaching to a surface, and from there, the cells grow and multiply. Strands of sugary material called extracellular polymeric substance are produced, and they attach the cell to the substance surface. This results in a matrix of cells and sugars that creates the slimy biofilm layer. These layers can range from a single cell to several inches thick.
Biofilms can negatively affect medical equipment and machinery by clogging mechanisms or reducing the effectiveness of antimicrobial agents.
After this lesson, you should have the ability to:
- Describe what a biofilm is
- Recall examples of where biofilms may be found
- Explain how biofilms are formed
- Understand how biofilms can impact our health
- Discuss how biofilms aid in bacterial survival
- Summarize some of the benefits of biofilms