Biofilms are collections of microorganisms in a matrix of extracellular polymeric material made up of polysaccharides, proteins, lipids, as well as nucleic acids. Many bacteria may transition among planktonic and biofilm forms. Planktonic bacteria have reproduction rates and relatively fast cell growth, which reduces their chances of survival but they are capable to different environments. The biofilm formation state appears to be a natural besides prevalent condition of microorganisms. The biofilm formation important since it increases bacterial tolerance to hostile environmental conditions lets microorganisms avoid being washed away by merely attaching to a surface or tissue, and most likely, by limiting thein diffusion, the extracellular polymeric matrix protects bacterial cells in deeper layers against antimicrobial agents. Primary contact/attachment to the surface, micro-colony development, maturity and construction of the biofilm architecture, and ultimately detachment and dispersion define the phases in biofilm formation. Once a biofilm is established, bacterial mobility decreases while cell density increases. Bacteria communicate within the biofilm through quorum sensing (QS), a signaling mechanism that regulates biofilm formation and the production of virulence factors. QS relies on the secretion and detection of autoinducers, which facilitate intercellular communication. In Gram-negative bacteria, the major QS signaling molecules include acyl-homoserine lactones (AHLs), autoinducing peptides (AIPs) in the Gram-positive bacteria and autoinducer-2 (AI-2), which is produced by both types of bacteria.
