Editing Epigenetics (section)

== Epigenetics in bacteria ==
[[File:Escherichia coli flagella TEM.png|thumb|''Escherichia coli'' bacteria]]
While epigenetics is of fundamental importance in [[eukaryote]]s, especially [[Multicellular organism|metazoans]], it plays a different role in bacteria.<ref>{{cite journal | vauthors = Oliveira PH | title = Bacterial Epigenomics: Coming of Age | journal = mSystems | volume = 6 | issue = 4 | pages = e0074721 | date = August 2021 | pmid = 34402642 | doi = 10.1128/mSystems.00747-21 | pmc = 8407109 | s2cid = 237149441 | doi-access = free }}</ref> Most importantly, eukaryotes use epigenetic mechanisms primarily to regulate gene expression which bacteria rarely do. However, bacteria make widespread use of postreplicative DNA methylation for the epigenetic control of DNA-protein interactions. Bacteria also use DNA [[adenine]] methylation (rather than DNA [[cytosine]] methylation) as an epigenetic signal. DNA adenine methylation is important in bacteria virulence in organisms such as ''[[Escherichia coli]]'', ''[[Salmonella]], [[Vibrio]], [[Yersinia]], [[Haemophilus]]'', and ''[[Brucella]]''. In ''[[Alphaproteobacteria]]'', methylation of adenine regulates the cell cycle and couples gene transcription to DNA replication. In ''[[Gammaproteobacteria]]'', adenine methylation provides signals for DNA replication, chromosome segregation, mismatch repair, packaging of bacteriophage, transposase activity and regulation of gene expression.<ref name="JorgTost" /><ref name="Casadesus">{{cite journal | vauthors = Casadesús J, Low D | title = Epigenetic gene regulation in the bacterial world | journal = Microbiology and Molecular Biology Reviews | volume = 70 | issue = 3 | pages = 830–56 | date = September 2006 | pmid = 16959970 | pmc = 1594586 | doi = 10.1128/MMBR.00016-06 }}</ref> There exists a genetic switch controlling ''[[Streptococcus pneumoniae]]'' (the pneumococcus) that allows the bacterium to randomly change its characteristics into six alternative states that could pave the way to improved vaccines. Each form is randomly generated by a phase variable methylation system. The ability of the pneumococcus to cause deadly infections is different in each of these six states. Similar systems exist in other bacterial genera.<ref name="MansoOggioni2014">{{cite journal | vauthors = Manso AS, Chai MH, Atack JM, Furi L, De Ste Croix M, Haigh R, Trappetti C, Ogunniyi AD, Shewell LK, Boitano M, Clark TA, Korlach J, Blades M, Mirkes E, Gorban AN, Paton JC, Jennings MP, Oggioni MR | title = A random six-phase switch regulates pneumococcal virulence via global epigenetic changes | journal = Nature Communications | volume = 5 | pages = 5055 | date = September 2014 | pmid = 25268848 | pmc = 4190663 | doi = 10.1038/ncomms6055 | bibcode = 2014NatCo...5.5055M }}</ref> In [[Bacillota]] such as ''[[Clostridioides difficile (bacteria)|Clostridioides difficile]],'' adenine methylation regulates [[Spore|sporulation]], [[biofilm]] formation and host-adaptation.<ref>{{cite journal | vauthors = Oliveira PH, Ribis JW, Garrett EM, Trzilova D, Kim A, Sekulovic O, Mead EA, Pak T, Zhu S, Deikus G, Touchon M, Lewis-Sandari M, Beckford C, Zeitouni NE, Altman DR, Webster E, Oussenko I, Bunyavanich S, Aggarwal AK, Bashir A, Patel G, Wallach F, Hamula C, Huprikar S, Schadt EE, Sebra R, van Bakel H, Kasarskis A, Tamayo R, Shen A, Fang G | title = Epigenomic characterization of Clostridioides difficile finds a conserved DNA methyltransferase that mediates sporulation and pathogenesis | journal = Nature Microbiology | volume = 5 | issue = 1 | pages = 166–180 | date = January 2020 | pmid = 31768029 | pmc = 6925328 | doi = 10.1038/s41564-019-0613-4 }}</ref>