What Are Biofilms? - Definition, Formation & Examples

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  • 0:02 What Are Biofilms?
  • 0:55 How Are Biofilms Formed?
  • 1:57 Biofilms that Affect Humans
  • 2:50 Biofilm Survival
  • 3:25 Biofilm Benefits
  • 3:55 Lesson Summary
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Lesson Transcript
Instructor: Paula Jacoby-Garrett
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.

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