Biofilm

A biofilm is a syntrophic community of microorganisms in which cells stick to each other and often also to a surface. These cells are surrounded by a slimy extracellular matrix made of extracellular polymeric substances (EPSs) that they produce themselves. This matrix is usually made of polysaccharides, proteins, lipids, and DNA. Because of their structure, biofilms have been compared to "cities for microbes," where the microbes can share nutrients and protect themselves from dangers like desiccation, toxins, antibiotics, and the immune system of a host body.

Biofilms can form on both living and non-living surfaces and are common in many places, such as nature, factories, and hospitals. They might form part of a larger microbiome. The cells in a biofilm behave differently from single cells, called planktonic cells, that float freely in liquid. For example, biofilms can form on the teeth of animals as dental plaque, which can lead to tooth decay and gum disease.

Microorganisms decide to form a biofilm because of various factors, such as finding a place to attach, getting enough food, or being exposed to small amounts of antibiotics. When a single cell attaches to a surface and starts growing, it can trigger a change in behavior that helps the group survive better. Biofilms can be made of just one type of microorganism or many different kinds, working together to stay strong and successful.

Origin and formation

Biofilms are thought to have started very early on Earth as a way for tiny organisms to survive harsh conditions. We can see them in fossils from about 3.25 billion years ago.

Biofilms form when tiny organisms, called microorganisms, stick to a surface. They first attach loosely and then more firmly using special structures. As more join, they create a slimy protective layer. This layer helps them hide from dangers and share food. They also talk to each other using chemical signals to coordinate their actions.

Development

Biofilms form through a process where tiny living things called microorganisms come together. They stick to each other and often to a surface, creating a community. This community is protected by a slimy layer made of substances they produce, which helps them share food and stay safe from harmful things in their environment.

Dispersal

Dispersal is an important part of a biofilm's life cycle. It allows biofilms to spread and colonize new surfaces. Certain enzymes, such as dispersin B and deoxyribonuclease, can break down the biofilm's slimy matrix, helping cells to leave. A fatty acid called cis-2-decenoic acid, produced by Pseudomonas aeruginosa, can also trigger dispersal and stop growth in some bacteria and yeast like Candida albicans. Nitric oxide Nitric oxide may help treat chronic infections caused by biofilms.

Previously, it was thought that cells leaving a biofilm would immediately start floating freely. However, research shows that these dispersed cells behave differently from free-floating cells. They can be more harmful to certain organisms but are also more sensitive to lack of iron. Biofilm dispersal involves complex processes, with bacteria sometimes leaving as single cells or in groups, affecting how they might cause new infections.

Properties

Biofilms are usually found on solid surfaces that are in water or very damp places. They can also float on top of liquids or grow on leaves in humid weather. If they have enough food, biofilms can grow big enough to see without a microscope. They can contain many kinds of tiny living things like bacteria, ancient microbes called archaea, tiny animals called protozoa, fungi, and algae. These organisms work together in special ways.

The goo that holds a biofilm together is made of sugars, proteins, and genetic material. This goo helps the tiny creatures talk to each other and share food. It can even trap helpful substances close to the cells. Because of this protection, bacteria in biofilms can sometimes resist medicines that would normally harm them. This makes it harder to treat infections caused by biofilms.

Habitats

Biofilms are found almost everywhere in nature. They form on rocks in streams, inside plants, and even in the human body. These slimy layers of tiny living things stick to surfaces and help share food among the organisms living there.

In places like water filters and sewage treatment plants, biofilms help clean water by trapping and breaking down harmful substances. They also live in our mouths as dental plaque, which can sometimes cause tooth decay if not removed regularly. Biofilms can survive in very hot or cold places, showing how tough and widespread they are in the world.

Taxonomic diversity

Many different bacteria form biofilms. These include both gram-positive bacteria like Bacillus and Staphylococcus and gram-negative bacteria like Escherichia coli and Pseudomonas aeruginosa. Cyanobacteria also form biofilms in water.

Biofilms can also be formed by other tiny living things, such as archaea and fungi like Cryptococcus laurentii. Diatoms, a type of microalgae, are also important in forming biofilms in both fresh and saltwater environments.

Infectious diseases

Biofilms play a big role in many infections in the body. They are linked to about 80% of all infections. This includes common issues like bacterial vaginosis, urinary tract infections, catheter infections, middle-ear infections, and dental plaque. They can also cause more serious problems such as endocarditis, infections in people with cystic fibrosis, and infections of medical devices like joint prostheses, heart valves, and intervertebral discs.

One important type of bacteria that forms biofilms is P. aeruginosa. It is often found in chronic infections like wounds, ear infections, and lung infections in people with cystic fibrosis. Another bacteria, Streptococcus pneumoniae, causes pneumonia and meningitis, especially in children and older adults. Escherichia coli biofilms are a common cause of urinary tract infections, particularly in hospitals. Staphylococcus aureus can infect the skin and lungs and form biofilms that help it resist treatments. Finally, Serratia marcescens forms biofilms on medical devices and in natural environments, making infections hard to treat.

Uses and impact

Biofilms play a big role in medicine because many bacterial infections involve them. These sticky layers of germs stick to surfaces like medical devices, making infections harder to cure. They can also make bacteria much stronger against medicines that try to kill them.

In other areas like water cleaning and making energy from waste, biofilms can be helpful. They help clean water in treatment plants and can even create electricity. But in food processing and fish farming, biofilms can cause problems by making it hard to keep food safe and clean. Scientists are working on new ways to stop harmful biofilms from forming.

Eukaryotic

See also: Phototrophic biofilms

Biofilms can also be created by eukaryotic microbes, which often work together with bacteria. Both fungi and microalgae can form these biofilms, laying down a slimy layer that helps protect all the tiny living things living there. In nature, fungi that live on plants help break down organic material and defend plants against harmful bacteria. In water, tiny plants called diatoms often start biofilms that may help them survive in cold or salty conditions. These diatom biofilms interact with many other tiny creatures, especially certain types of bacteria, in an area called the phycosphere.

Horizontal gene transfer

Horizontal gene transfer is when animals or other small living things share their genes with each other in a way that is not from parent to child. This happens more often in tiny living things called prokaryotes than in others. In bacteria, this can happen in a few ways: by taking up free DNA from the environment, through viruses, or by connecting directly with tiny hair-like structures.

Biofilms, which are groups of tiny living things stuck together, help this gene sharing happen. They bring bacteria close together, making it easier for them to swap genes. This can help bacteria become stronger or more resistant to medicines. For example, bacteria in biofilms can share genes that help them stick together better or fight off harmful substances. This sharing is important for the survival and growth of these tiny communities.

Cultivation devices

Scientists use many different tools to grow and study biofilms in laboratories. These tools help them understand how biofilms behave in natural or industrial settings. Some common devices include microtiter plate systems, BioFilm Ring Tests, Robbins Devices, Drip Flow Biofilm Reactors, rotary devices like the CDC Biofilm Reactor, flow chambers, and microfluidic approaches. Each device offers unique ways to observe and analyze biofilm growth and characteristics.