Editing Helicobacter pylori (section)

===Genome===
''Helicobacter pylori'' consists of a large diversity of strains, and hundreds of [[genome]]s have been completely [[sequencing|sequenced]].<ref>{{cite web |url=http://genolist.pasteur.fr/PyloriGene |title=Genome information for the ''H.&nbsp;pylori'' 26695 and J99 strains |publisher=Institut Pasteur |year=2002 |access-date=1 September 2008 |archive-date=26 November 2017 |archive-url=https://web.archive.org/web/20171126221437/http://genolist.pasteur.fr/PyloriGene/ |url-status=live }}</ref><ref>{{cite web |url=https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=genome&cmd=Retrieve&dopt=Overview&list_uids=139 |title=''Helicobacter pylori'' J99, complete genome |publisher=National Center for Biotechnology Information |access-date=1 September 2008 |archive-date=6 April 2011 |archive-url=https://web.archive.org/web/20110406134345/http://www.ncbi.nlm.nih.gov/sites/entrez?db=genome |url-status=live }}</ref><ref name="Oh">{{cite journal | vauthors = Oh JD, Kling-Bäckhed H, Giannakis M, Xu J, Fulton RS, Fulton LA, Cordum HS, Wang C, Elliott G, Edwards J, Mardis ER, Engstrand LG, Gordon JI | title = The complete genome sequence of a chronic atrophic gastritis Helicobacter pylori strain: evolution during disease progression | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 26 | pages = 9999–10004 | date = June 2006 | pmid = 16788065 | pmc = 1480403 | doi = 10.1073/pnas.0603784103 | bibcode = 2006PNAS..103.9999O | doi-access = free }}</ref> The genome of the strain ''26695'' consists of about 1.7&nbsp;million [[base pair]]s, with some 1,576&nbsp;genes.<ref name="NCBI">{{cite web |title=Helicobacter pylori 26695 genome assembly ASM30779v1 |url=https://www.ncbi.nlm.nih.gov/datasets/genome/GCF_000307795.1/ |website=NCBI |access-date=4 June 2024 |language=en}}</ref><ref name="Tomb 1997">{{cite journal | vauthors = Tomb JF, White O, Kerlavage AR, Clayton RA, Sutton GG, Fleischmann RD, Ketchum KA, Klenk HP, Gill S, Dougherty BA, Nelson K, Quackenbush J, Zhou L, Kirkness EF, Peterson S, Loftus B, Richardson D, Dodson R, Khalak HG, Glodek A, McKenney K, Fitzegerald LM, Lee N, Adams MD, Hickey EK, Berg DE, Gocayne JD, Utterback TR, Peterson JD, Kelley JM, Cotton MD, Weidman JM, Fujii C, Bowman C, Watthey L, Wallin E, Hayes WS, Borodovsky M, Karp PD, Smith HO, Fraser CM, Venter JC | title = The complete genome sequence of the gastric pathogen Helicobacter pylori | journal = Nature | volume = 388 | issue = 6642 | pages = 539–47 | date = August 1997 | pmid = 9252185 | doi = 10.1038/41483 | s2cid = 4411220 | bibcode = 1997Natur.388..539T | doi-access = free }}</ref> The [[pan-genome]], that is the combined set of 30&nbsp;sequenced strains, encodes 2,239&nbsp;protein families ([[Sequence homology#Orthology|orthologous groups]] OGs).<ref>{{cite journal | vauthors = van Vliet AH | title = Use of pan-genome analysis for the identification of lineage-specific genes of Helicobacter pylori | journal = FEMS Microbiology Letters | volume = 364 | issue = 2 | pages = fnw296 | date = January 2017 | pmid = 28011701 | doi = 10.1093/femsle/fnw296 | doi-access = free }}</ref> Among them, 1,248&nbsp;OGs are conserved in all the 30&nbsp;strains, and represent the [[Pan-genome#Core|universal core]]. The remaining 991&nbsp;OGs correspond to the [[Pan-genome#Cloud|accessory genome]] in which 277&nbsp;OGs are unique to one strain.<ref>{{cite journal | vauthors = Uchiyama I, Albritton J, Fukuyo M, Kojima KK, Yahara K, Kobayashi I | title = A Novel Approach to Helicobacter pylori Pan-Genome Analysis for Identification of Genomic Islands | journal = PLOS ONE | volume = 11 | issue = 8 | pages = e0159419 | date = 9 August 2016 | pmid = 27504980 | pmc = 4978471 | doi = 10.1371/journal.pone.0159419 | bibcode = 2016PLoSO..1159419U | doi-access = free }}</ref>

There are eleven [[restriction modification system]]s in the genome of ''H. pylori''.<ref name="Tomb 1997" /> This is an unusually high number providing a [[DNA methylation#In bacteria|defence against bacteriophages]].<ref name="Tomb 1997" />