SCIENCE

Let’s stick together: the basics of bacterial biofilms

Betty Zou, Ph D.

Like many humans, bacteria can have an active or sedentary lifestyle. In their active or planktonic state, bacteria use their various appendages to propel themselves in different directions towards food or away from danger. When conditions are right, they switch gears and adopt a slow living lifestyle where they settle down and build a biofilm.

 

Haven’t heard of biofilms? Unlike what the name suggests, a biofilm is not some new genre of biographical movie on Netflix. It’s actually a community of microbes that lives and grows on a surface. A biofilm can be made entirely of bacteria from one single species or, more commonly, it comprises a variety of bacterial and fungal inhabitants.

 

Another important feature of biofilms is the sticky 3-D structure that encases the microbes. Made of sugars, proteins and fats, this matrix provides the support infrastructure needed to stabilize the biofilm and allow it to adhere to a surface. It also serves as a fortress wall, shielding the microbial citizens inside from attack by chemicals, enzymes and other microbe-killing compounds.

 

Biofilms can form on any hard surface and once they are established, they are notoriously hard to remove. Not only are the bacteria inside physically protected from antibiotics, but they are also in a hibernation-like state where their metabolism slows down and makes them less susceptible to any antibiotics that do get through. These factors make biofilms especially dangerous in a hospital setting wherethey can form on medical devices like catheters, scopes and heart valves and cause infections in patients.

 

Perhaps the most well-known, and well-studied, biofilm is dental plaque. Biofilms are especially important to oral bacteria because it anchors them to a surface—in this case, teeth—and prevents them from being swept away by the steady stream of saliva down Esophagus Falls.

 

Oral biofilms like plaque typically contain many different species of bacteria. Most are harmless or even beneficial to our health but some are known to cause tooth decay, cavities and periodontal disease. The way in which these bacteria assemble together to form a biofilm is structured and orderly. The first settlers are microbes that are able to stick directly to tooth enamel. Next come the early colonizers—bacteria that attach themselves to the microbial pioneers—followed by the late colonizers. In each case, the interaction between two bacterial species is highly specific. Most bacteria are only able to connect with a few other species but some can form liaisons with many different partners. These promiscuous bacteria serve as important bridge species that help connect all the different biofilm inhabitants.

 

Dental plaque at healthy sites differs in their microbial makeup from plaque isolated from diseased sites. Beneficial bacteria that help maintain a near neutral pH and keep pathogens at bay dominate the biofilm at healthy sites. In contrast, plaque from unhealthy sites has more harmful bacteria than good bacteria. These acid-producing and acid-loving microbes metabolize sugars to acid andcause the pH within their biofilm communities to drop to near 5, the point at which the underlying tooth enamel starts to break down.

 

Regular teeth cleaning can remove oral biofilms but doesn’t prevent bacteria from re-colonizing the tooth enamel. These oral microbes possess a stick-to-itiveness that, were it not for the potential harm they cause, would be worthy of admiration.

Betty Zou, Ph D.

Scientist turned science writer and communicator. I turn complex scientific concepts and studies into clear and engaging content for diverse lay audiences. Previous work include blog posts, news articles and releases, patient and customer profiles, feature length stories, donor reports and marketing materials. My areas of expertise are molecular biology, microbiology and microbiome-related topics but I have also written extensively about other health and medicine topics such as cancer, cardiology and trauma.

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