biofilm: a standalone construct

The microbiologist J. William Costerton and colleagues brought the term biofilm into wide scientific use beginning with their 1978 Scientific American essay How bacteria stick, which argued that most bacteria in nature do not float freely but live attached to surfaces inside a sticky coating they secrete. A biofilm is a structured community of microorganisms, often many species together, that adhere to a surface or to one another and are held within a self-produced matrix of extracellular polymeric substances, a hydrated mesh of polysaccharides, proteins, and DNA that the cells build around themselves. Surface-attached bacterial communities had been documented earlier, notably by Claude ZoBell in 1943, who showed that solid surfaces in seawater concentrate bacterial activity, and centuries before that Antonie van Leeuwenhoek observed the living microbes in scrapings from teeth, but the biofilm concept gathered these observations under one named mode of microbial life. Costerton and colleagues' 1995 synthesis in the Annual Review of Microbiology set out the modern account, in which cells within the matrix communicate, differentiate, and become far more tolerant of antibiotics and host defenses than the same cells growing free in suspension. The construct is a landmark because it reframes the default state of bacterial existence from the isolated, free-swimming cell of classical laboratory culture to the attached, matrix-embedded community that predominates in natural, industrial, and clinical settings, from dental plaque and chronic wounds to water pipes and ship hulls.[1][2][3]

Unit

A named mode of microbial life: a surface-attached community of microbes held in a self-produced extracellular matrix

Recovery means

Not applicable

Measured by

Identified by microscopy of attached communities (including confocal and electron microscopy), by staining of the extracellular matrix, and by viable-cell counts, and distinguished from free-floating planktonic cells by surface attachment and the presence of matrix