Biofilms are assemblages of bacteria attached to a surface and enclosed in an adhesive matrix. The matrix is made of polysaccharides, proteins, and nucleic acids. These molecules prevent the detachment of cells from surfaces.  Typically biofilms contain many types of bacteria, but can sometimes include only one or two. The biofilm in the mouth, covering the teeth is known to contain as many as 7oo phylotypes of bot archaea and bacteria.

Biofilms form through random collision of cells with a surface. Attachment happens through interactions with the surface and other cells. Before bacteria form a biofilm, they are known, individually, as planktonic cells. Once these cells attach to a surface to form a biofilm,  the bacteria will loose is flagella and become nonmotile.  Cyclic di- guanosine monophosphate is responsible for triggering the transition for plankton into a  biofilm.

Bacteria form biofilm for many reasons. Biofilms increase survival, as it is a means of microbial self-defense, they are resistant to forces that try to remove them from their environment or disconnect them from a surface. Biofilms are resistant to phagocytosis and the immune system of cells. The biofilm allows cells to stay in a certain niche. Another reason biofilms form is because of the close proximity of bacteria cells. Cell to cell communication assists in the survival of the bacteria and the biofilm. Lastly, bacteria from biofilms because it is the default mode of growth in nature. Biofilms are full of nutrients so of course, they are a more typical growth medium for bacteria. You will find individual planktonic cells only if there is a low availability of nutrients in the environment.

Biofilms can be harmful to humans and human lifestyle. They are resistant to the immune system in the body and not all antibiotics, and other microbial agents can penetrate the biofilm. Biofilms have been known to cause cystic fibrosis and are implicated in dental and medical conditions. Biofilms cover medical implants like catheters or artificial joints, causing infection. Biofilms also cause issues in the industrial industry, as they form in pipes and pipelines. The biofilm can cause corrosion of the pipes and cause water in the pipes to become carriers for pathogenic bacteria, like cholera if colonized by the pathogenic agent. Chlorine is used to kill the unwanted bacteria, but it is not always effective.