Biofilm

A biofilm is a community of microorganisms where the cells stick to each other and often to a surface. These cells are surrounded by a slimy covering made of different substances that they produce. This covering is usually made of polysaccharides, proteins, lipids, and DNA. Because of how they are built, biofilms are sometimes called "cities for microbes." In these cities, microbes can share what they need to grow and protect themselves from dangers like toxins, antibiotics, and the immune system of a host body.

Biofilms can form on both living and non-living surfaces. You can find them in nature, factories, and hospitals. They might be 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 form biofilms for many reasons, such as finding a place to stay, getting enough food, or dealing with small amounts of antibiotics. When a single cell attaches to a surface and starts to grow, it can cause a change 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.

Origin and formation

Biofilms may have begun very early on Earth to help tiny organisms survive tough conditions. We can find 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 make a slimy protective layer. This layer helps them hide from dangers and share food. They also send each other chemical signals to work together.

Development

Biofilms form when tiny living things called microorganisms come together. They stick to each other and to a surface, creating a community. This community is protected by a slimy layer they make. This layer helps them share food and stay safe from harmful things around them.

Dispersal

Dispersal is an important part of a biofilm's life cycle. It helps biofilms spread to new surfaces. Certain enzymes, such as dispersin B and deoxyribonuclease, can break down the slimy matrix of the biofilm, allowing cells to leave. A fatty acid called cis-2-decenoic acid, made 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. Research now shows that these dispersed cells act differently from free-floating cells. Biofilm dispersal involves complex processes, with bacteria sometimes leaving as single cells or in groups.

Properties

Biofilms are often found on solid surfaces in water or very damp places. They can also float on top of liquids or grow on leaves when the weather is humid. 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 also trap helpful substances close to the cells. Because of this protection, bacteria in biofilms can sometimes resist medicines that would normally stop 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 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 can cause many infections in the body. They are linked to infections such as bacterial vaginosis, urinary tract infections, catheter infections, middle-ear infections, and dental plaque. They can also cause 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 are important in medicine because many infections involve them. These sticky layers of germs stick to surfaces like medical devices, making infections harder to treat. They can also make bacteria stronger against medicines.

In other areas like cleaning water 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 looking for new ways to stop harmful biofilms from forming.

Eukaryotic

See also: Phototrophic biofilms

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

Horizontal gene transfer

Horizontal gene transfer is when small living things share their genes with each other outside of normal parent-to-child inheritance. This happens more often in tiny organisms called prokaryotes. In bacteria, gene sharing can occur in a few ways: by picking up free DNA from the environment, through viruses, or by connecting directly with special hair-like structures.

Biofilms, which are groups of tiny organisms stuck together, make this gene sharing easier. They bring bacteria close together, helping them swap genes. This can help bacteria grow stronger or resist medicines. For example, bacteria in biofilms can share genes that help them stick together or protect themselves. This sharing is important for the growth and survival of these tiny communities.

Cultivation devices

Scientists use special tools to grow and study biofilms in laboratories. These tools help them learn how biofilms act in nature or in factories. Some common tools 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 tool gives scientists different ways to watch and study how biofilms grow and change.