Editing Biofilm (section)

=== Dental plaque ===
Within the human body, biofilms are present on the [[teeth]] as [[dental plaque]], where they may cause [[tooth decay]] and [[gum disease]]. These biofilms can either be in an uncalcified state that can be removed by dental instruments, or a calcified state which is more difficult to remove. Removal techniques can also include [[antimicrobial]]s.<ref>{{cite journal | vauthors = Chandki R, Banthia P, Banthia R | title = Biofilms: A microbial home | journal = Journal of Indian Society of Periodontology | volume = 15 | issue = 2 | pages = 111–4 | date = April 2011 | pmid = 21976832 | pmc = 3183659 | doi = 10.4103/0972-124X.84377 | doi-access = free }}</ref>

Dental plaque is an oral biofilm that adheres to the teeth and consists of many species of both bacteria and fungi (such as ''[[Streptococcus mutans]]'' and ''Candida albicans''), embedded in salivary [[polymers]] and microbial extracellular products. The accumulation of microorganisms subjects the teeth and gingival tissues to high concentrations of bacterial [[metabolite]]s which results in dental disease.<ref name="RevistaOMF">{{cite journal | vauthors = Augustin M, Chifiriuc CB, Lazăr V, Stănescu R, Burlibașa M, Ispas DC |date=December 2010|title=Microbial biofilms in dental medicine in reference to implanto-prostethic rehabilitation|url=http://www.revistaomf.ro/(8)|journal=Revista de Chirurgie Oro-maxilo-facială și Implantologie|language=ro|volume=1|issue=1|pages=9–13|issn=2069-3850|id=8 |access-date=3 June 2012}}{{Dead link|date=June 2019 |bot=InternetArchiveBot |fix-attempted=yes }}(webpage has a translation button)</ref> Biofilm on the surface of teeth is frequently subject to oxidative stress<ref name="pmid8519478">{{cite journal | vauthors = Marquis RE | title = Oxygen metabolism, oxidative stress and acid-base physiology of dental plaque biofilms | journal = Journal of Industrial Microbiology | volume = 15 | issue = 3 | pages = 198–207 | date = September 1995 | pmid = 8519478 | doi = 10.1007/bf01569826 | s2cid = 19959528 | doi-access = free }}</ref> and acid stress.<ref name="Lemos">{{cite journal | vauthors = Lemos JA, Abranches J, Burne RA | title = Responses of cariogenic streptococci to environmental stresses | journal = Current Issues in Molecular Biology | volume = 7 | issue = 1 | pages = 95–107 | date = January 2005 | pmid = 15580782 | url = http://www.horizonpress.com/cimb/v/v7/07.pdf | access-date = 3 April 2014 | archive-date = 7 April 2014 | archive-url = https://web.archive.org/web/20140407114140/http://www.horizonpress.com/cimb/v/v7/07.pdf | url-status = dead }}</ref> Dietary carbohydrates can cause a dramatic decrease in pH in oral biofilms to values of 4 and below (acid stress).<ref name="Lemos" /> A pH of 4 at body temperature of 37&nbsp;°C causes [[depurination]] of DNA, leaving apurinic (AP) sites in DNA,<ref name="pmid14938354">{{cite journal | vauthors = Tamm C, Hodes ME, Chargaff E | title = The formation apurinic acid from the desoxyribonucleic acid of calf thymus | journal = The Journal of Biological Chemistry | volume = 195 | issue = 1 | pages = 49–63 | date = March 1952 | doi = 10.1016/S0021-9258(19)50874-2 | pmid = 14938354 | doi-access = free }}</ref> especially loss of guanine.<ref name="pmid13701660">{{cite journal | vauthors = Freese EB | title = Transitions and transversions induced by depurinating agents | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 47 | issue = 4 | pages = 540–5 | date = April 1961 | pmid = 13701660 | pmc = 221484 | doi = 10.1073/pnas.47.4.540 | bibcode = 1961PNAS...47..540B | doi-access = free }}</ref>

Dental plaque biofilm can result in [[Tooth decay|dental caries]] if it is allowed to develop over time. An ecologic shift away from balanced populations within the dental biofilm is driven by certain (cariogenic) microbiological populations beginning to dominate when the environment favors them. The shift to an [[acidogenic]], aciduric, and cariogenic microbiological population develops and is maintained by frequent consumption of fermentable dietary [[carbohydrate]]. The resulting activity shift in the biofilm (and resulting acid production within the biofilm, at the tooth surface) is associated with an imbalance of demineralization over remineralization, leading to net mineral loss within dental hard tissues ([[Tooth enamel|enamel]] and then [[dentin]]), the symptom being a [[carious lesion]], or cavity. By preventing the dental plaque biofilm from maturing or by returning it back to a non-cariogenic state, dental caries can be prevented and arrested.<ref name="Pennwell">Pennwell, "Toothbrush technology, dentifrices and dental biofilm removal." ''Dental Academy of CE'' Accessed 12 January 2022</ref><ref>{{cite book|title=Pathology of dental caries. In: Dental caries: the disease and its clinical management.| vauthors = Fejerskov O |publisher=Oxford (UK): Wiley Blackwell|year=2015|isbn=978-1-4051-3889-5|pages=7–9}}</ref> This can be achieved through the behavioral step of reducing the supply of fermentable carbohydrates (i.e. sugar intake) and frequent removal of the biofilm (i.e., [[Tooth brushing|toothbrushing]]).<ref name="Pennwell"/>

====Intercellular communication====
{{See also|Oral microbiology}}
A peptide pheromone quorum sensing signaling system in ''[[S. mutans]]'' includes the [[Oral microbiology#Intercellular communication|competence stimulating peptide]] (CSP) that controls genetic competence.<ref name="Li">{{cite journal|date=February 2001|title=Natural genetic transformation of Streptococcus mutans growing in biofilms|journal=J. Bacteriol.|volume=183|issue=3|pages=897–908|doi=10.1128/JB.183.3.897-908.2001|pmc=94956|pmid=11208787|vauthors=Li YH, Lau PC, Lee JH, Ellen RP, Cvitkovitch DG}}</ref><ref name="pmid18792689">{{cite book|year=2008|series=Advances in Experimental Medicine and Biology|volume=631|pages=[https://archive.org/details/bacterialsignalt0000unse/page/178 178–88]|doi=10.1007/978-0-387-78885-2_12|isbn=978-0-387-78884-5|pmid=18792689|vauthors=Senadheera D, Cvitkovitch DG|chapter=Quorum Sensing and Biofilm Formation by Streptococcus mutans |title=Bacterial Signal Transduction: Networks and Drug Targets|chapter-url=https://archive.org/details/bacterialsignalt0000unse/page/178}}</ref> Genetic competence is the ability of a cell to take up DNA released by another cell. Competence can lead to genetic transformation, a form of sexual interaction, favored under conditions of high cell density and/or stress where there is maximal opportunity for interaction between the competent cell and the DNA released from nearby donor cells. This system is optimally expressed when ''S. mutans'' cells reside in an actively growing biofilm. Biofilm grown ''S. mutans'' cells are genetically transformed at a rate 10- to 600-fold higher than ''S. mutans'' growing as free-floating planktonic cells suspended in liquid.<ref name="Li" />

When the biofilm, containing ''S. mutans'' and related oral streptococci, is subjected to acid stress, the competence regulon is induced, leading to resistance to being killed by acid.<ref name="Lemos" /> As pointed out by Michod et al., transformation in bacterial pathogens likely provides for effective and efficient recombinational repair of DNA damages.<ref name="Michod">{{cite journal|date=May 2008|title=Adaptive value of sex in microbial pathogens|journal=Infect. Genet. Evol.|volume=8|issue=3|pages=267–85|doi=10.1016/j.meegid.2008.01.002|pmid=18295550|vauthors=Michod RE, Bernstein H, Nedelcu AM|bibcode=2008InfGE...8..267M }}http://www.hummingbirds.arizona.edu/Faculty/Michod/Downloads/IGE%20review%20sex.pdf {{Webarchive|url=https://web.archive.org/web/20200511153411/http://www.hummingbirds.arizona.edu/Faculty/Michod/Downloads/IGE%20review%20sex.pdf |date=11 May 2020 }}</ref> It appears that ''S. mutans'' can survive the frequent acid stress in oral biofilms, in part, through the recombinational repair provided by competence and transformation.

'''Predator-prey interactions'''

{{See also|Lotka–Volterra equations|l1=Predator-prey interactions}}

[[Predation|Predator]]-[[Predation|prey]] interactions between biofilms and bacterivores, such as the soil-dwelling nematode ''[[Caenorhabditis elegans]],'' had been extensively studied. Via the production of sticky matrix and formation of aggregates, ''[[Yersinia pestis]]'' biofilms can prevent feeding by obstructing the mouth of ''C. elegans''.<ref>{{cite journal | vauthors = Atkinson S, Goldstone RJ, Joshua GW, Chang CY, Patrick HL, Cámara M, Wren BW, Williams P | title = Biofilm development on Caenorhabditis elegans by Yersinia is facilitated by quorum sensing-dependent repression of type III secretion | journal = PLOS Pathogens | volume = 7 | issue = 1 | pages = e1001250 | date = January 2011 | pmid = 21253572 | pmc = 3017118 | doi = 10.1371/journal.ppat.1001250 | doi-access = free }}</ref> Moreover, ''[[Pseudomonas aeruginosa]]'' biofilms can impede the slithering motility of ''C. elegans'', termed as 'quagmire phenotype', resulting in trapping of ''C. elegans'' within the biofilms and preventing the exploration of nematodes to feed on susceptible biofilms.<ref>{{cite journal | vauthors = Chan SY, Liu SY, Seng Z, Chua SL | title = Biofilm matrix disrupts nematode motility and predatory behavior | journal = The ISME Journal | pages = 260–269 | date = September 2020 | volume = 15 | issue = 1 | pmid = 32958848 | doi = 10.1038/s41396-020-00779-9 | pmc = 7852553 | url = }}</ref> This significantly reduced the ability of predator to feed and reproduce, thereby promoting the survival of biofilms. ''Pseudomonas aeruginosa'' biofilms can also mask their chemical signatures, where they reduced the diffusion of quorum sensing molecules into the environment and prevented the detection of ''C. elegans''.<ref>{{cite journal | vauthors = Li S, Liu SY, Chan SY, Chua SL | title = Biofilm matrix cloaks bacterial quorum sensing chemoattractants from predator detection | journal = The ISME Journal | volume = 16 | issue = 5 | pages = 1388–1396 | date = May 2022 | pmid = 35034106 | pmc = 9038794 | doi = 10.1038/s41396-022-01190-2 | bibcode = 2022ISMEJ..16.1388L }}</ref>