Editing Biofilm (section)

=== Extracellular matrix ===
[[File:Mixed-culture biofilm.jpg|thumb|Scanning electron micrograph of mixed-culture biofilm, demonstrating in detail a spatially heterogeneous arrangement of bacterial cells and extracellular polymeric substances.]]
The EPS matrix consists of [[exopolysaccharides]], proteins and nucleic acids.<ref name="JMB"/><ref>{{cite journal | vauthors = Danese PN, Pratt LA, Kolter R | title = Exopolysaccharide production is required for development of Escherichia coli K-12 biofilm architecture | journal = Journal of Bacteriology | volume = 182 | issue = 12 | pages = 3593–6 | date = June 2000 | pmid = 10852895 | pmc = 101973 | doi = 10.1128/jb.182.12.3593-3596.2000 }}</ref><ref>{{cite journal | vauthors = Branda SS, Chu F, Kearns DB, Losick R, Kolter R | title = A major protein component of the Bacillus subtilis biofilm matrix | journal = Molecular Microbiology | volume = 59 | issue = 4 | pages = 1229–38 | date = February 2006 | pmid = 16430696 | doi = 10.1111/j.1365-2958.2005.05020.x | s2cid = 3041295 | doi-access = free }}</ref> A large proportion of the EPS is more or less strongly hydrated, however, hydrophobic EPS also occur; one example is cellulose<ref>{{cite journal | vauthors = Choong FX, Bäck M, Fahlén S, Johansson LB, Melican K, Rhen M, Nilsson KP, Richter-Dahlfors A | title = Salmonella biofilms using luminescent oligothiophenes | journal = npj Biofilms and Microbiomes | volume = 2 | pages = 16024 | date = 23 November 2016 | pmid = 28721253 | pmc = 5515270 | doi = 10.1038/npjbiofilms.2016.24 }}</ref> which is produced by a range of microorganisms. This matrix encases the cells within it and facilitates communication among them through biochemical signals as well as gene exchange. The EPS matrix also traps extracellular enzymes and keeps them in close proximity to the cells. Thus, the matrix represents an external digestion system and allows for stable synergistic microconsortia of different species.<ref name="Wingender">{{cite journal | vauthors = Flemming HC, Wingender J, Szewzyk U, Steinberg P, Rice SA, Kjelleberg S | title = Biofilms: an emergent form of bacterial life | journal = Nature Reviews. Microbiology | volume = 14 | issue = 9 | pages = 563–75 | date = August 2016 | pmid = 27510863 | doi = 10.1038/nrmicro.2016.94 | s2cid = 4384131 }}</ref> Some biofilms have been found to contain water channels that help distribute [[nutrient]]s and signalling molecules.<ref>{{cite journal | vauthors = Stoodley P, Debeer D, Lewandowski Z | title = Liquid flow in biofilm systems | journal = Applied and Environmental Microbiology | volume = 60 | issue = 8 | pages = 2711–6 | date = August 1994 | pmid = 16349345 | pmc = 201713 | doi = 10.1128/aem.60.8.2711-2716.1994 | bibcode = 1994ApEnM..60.2711S }}</ref> This matrix is strong enough that under certain conditions, biofilms can become [[fossil]]ized ([[stromatolite]]s).

Bacteria living in a biofilm usually have significantly different properties from free-floating bacteria of the same species, as the dense and protected environment of the film allows them to cooperate and interact in various ways.<ref>{{cite journal | vauthors = Vlamakis H, Aguilar C, Losick R, Kolter R | title = Control of cell fate by the formation of an architecturally complex bacterial community | journal = Genes & Development | volume = 22 | issue = 7 | pages = 945–53 | date = April 2008 | pmid = 18381896 | pmc = 2279205 | doi = 10.1101/gad.1645008 }}</ref> One benefit of this environment is increased resistance to [[detergent]]s and [[antibiotic]]s, as the dense extracellular matrix and the outer layer of cells protect the interior of the community.<ref>{{cite journal | vauthors = Stewart PS, Costerton JW | title = Antibiotic resistance of bacteria in biofilms | journal = Lancet | volume = 358 | issue = 9276 | pages = 135–8 | date = July 2001 | pmid = 11463434 | doi = 10.1016/S0140-6736(01)05321-1 | s2cid = 46125592 | url = https://scholarworks.montana.edu/xmlui/handle/1/13570 }}</ref><ref name="Pandey">{{cite journal |vauthors=Pandey R, Mishra SK, Shrestha A |title=Characterisation of ESKAPE Pathogens with Special Reference to Multidrug Resistance and Biofilm Production in a Nepalese Hospital |journal=Infect Drug Resist |volume=14 |issue= |pages=2201–2212 |date=2021 |pmid=34163185 |pmc=8214009 |doi=10.2147/IDR.S306688 |url= |doi-access=free }}</ref> In some cases [[antibiotic resistance]] can be increased up to 5,000 times.<ref name="Del Pozo"/> [[Lateral gene transfer]] is often facilitated within bacterial and archaeal biofilms<ref name="Chimileski 65">{{cite journal | vauthors = Chimileski S, Franklin MJ, Papke RT | title = Biofilms formed by the archaeon Haloferax volcanii exhibit cellular differentiation and social motility, and facilitate horizontal gene transfer | journal = BMC Biology | volume = 12 | pages = 65 | date = August 2014 | pmid = 25124934 | pmc = 4180959 | doi = 10.1186/s12915-014-0065-5 | doi-access = free }}</ref> and can lead to a more stable biofilm structure.<ref>{{cite journal | vauthors = Molin S, Tolker-Nielsen T | title = Gene transfer occurs with enhanced efficiency in biofilms and induces enhanced stabilisation of the biofilm structure | journal = Current Opinion in Biotechnology | volume = 14 | issue = 3 | pages = 255–61 | date = June 2003 | pmid = 12849777 | doi = 10.1016/S0958-1669(03)00036-3 }}</ref> Extracellular DNA is a major structural component of many different microbial biofilms.<ref name="Jakubovics">{{cite journal | vauthors = Jakubovics NS, Shields RC, Rajarajan N, Burgess JG | title = Life after death: the critical role of extracellular DNA in microbial biofilms | journal = Letters in Applied Microbiology | volume = 57 | issue = 6 | pages = 467–75 | date = December 2013 | pmid = 23848166 | doi = 10.1111/lam.12134 | s2cid = 206168952 | doi-access = free }}</ref> Enzymatic degradation of extracellular DNA can weaken the biofilm structure and release microbial cells from the surface.

However, biofilms are not always less susceptible to antibiotics. For instance, the biofilm form of ''[[Pseudomonas aeruginosa]]'' has no greater resistance to antimicrobials than do stationary-phase planktonic cells, although when the biofilm is compared to logarithmic-phase planktonic cells, the biofilm does have greater resistance to antimicrobials. This resistance to antibiotics in both stationary-phase cells and biofilms may be due to the presence of [[persister cell]]s.<ref>{{cite journal|vauthors=Spoering AL, Lewis K |title=Biofilms and planktonic cells of Pseudomonas aeruginosa have similar resistance to killing by antimicrobials |journal=Journal of Bacteriology |volume=183 |issue=23 |pages=6746–51 |date=December 2001 |pmid=11698361 |pmc=95513 |doi=10.1128/JB.183.23.6746-6751.2001}}</ref>