Editing Escherichia coli (section)

==Diversity==
[[File:E.coli on growing on various agar media.jpg|alt=E. coli colonies|thumb|''E. coli growing on basic cultivation media'']]
''E. coli'' encompasses an enormous population of bacteria that exhibit a very high degree of both genetic and phenotypic diversity. [[Whole genome sequencing|Genome sequencing]] of many isolates of ''E. coli'' and related bacteria shows that a taxonomic reclassification would be desirable. However, this has not been done, largely due to its medical importance,<ref>{{cite book | veditors = Krieg NR, Holt JG |title=Bergey's Manual of Systematic Bacteriology |edition=First |volume=1 |publisher=The Williams & Wilkins Co |location=Baltimore |year=1984 |pages=408–20 |isbn=978-0-683-04108-8 }}</ref> and ''E. coli'' remains one of the most diverse bacterial species: only 20% of the genes in a typical ''E. coli'' genome is shared among all strains.<ref name="comparison">{{cite journal | vauthors = Lukjancenko O, Wassenaar TM, Ussery DW | title = Comparison of 61 sequenced Escherichia coli genomes | journal = Microbial Ecology | volume = 60 | issue = 4 | pages = 708–20 | date = November 2010 | pmid = 20623278 | pmc = 2974192 | doi = 10.1007/s00248-010-9717-3 | bibcode = 2010MicEc..60..708L }}</ref>

In fact, from the more constructive point of view, the members of genus ''Shigella'' (''S. dysenteriae'', ''S. flexneri'', ''S. boydii'', and ''S. sonnei'') should be classified as ''E. coli'' strains, a phenomenon termed [[taxa in disguise]].<ref name="pmid12361912">{{cite journal | vauthors = Lan R, Reeves PR | title = Escherichia coli in disguise: molecular origins of ''Shigella'' | journal = Microbes and Infection | volume = 4 | issue = 11 | pages = 1125–32 | date = September 2002 | pmid = 12361912 | doi = 10.1016/S1286-4579(02)01637-4 }}</ref> Similarly, other strains of ''E. coli'' (e.g. the [[E. coli K-12|K-12]] strain commonly used in [[recombinant DNA]] work) are sufficiently different that they would merit reclassification.

A [[strain (biology)|strain]] is a [[subgroup]] within the species that has unique characteristics that distinguish it from other [[Strain (biology)|strains]]. These differences are often detectable only at the molecular level; however, they may result in changes to the physiology or lifecycle of the bacterium. For example, a strain may gain [[pathogenicity|pathogenic capacity]], the ability to use a unique [[carbon source (biology)|carbon source]], the ability to take upon a particular [[ecological niche]], or the ability to resist [[antimicrobial agents]]. Different strains of ''E. coli'' are often host-specific, making it possible to determine the source of fecal contamination in environmental samples.<ref name="Feng_2002" /><ref name="Thompson" /> For example, knowing which ''E. coli'' strains are present in a water sample allows researchers to make assumptions about whether the contamination originated from a human, another [[mammal]], or a [[bird]].

===Serotypes===
{{main|Pathogenic Escherichia coli#Serotypes}}

[[File:Escherichia coli on agar.jpg|alt=E.coli colonies on agar.|thumb|''E. coli'' on sheep blood agar]]
A common subdivision system of ''E. coli'', but not based on evolutionary relatedness, is by serotype, which is based on major surface [[antigen]]s (O antigen: part of [[lipopolysaccharide]] layer; H: [[flagellin]]; K [[antigen]]: capsule), e.g. [[O157:H7]]).<ref name="pmid334154">{{cite journal | vauthors = Orskov I, Orskov F, Jann B, Jann K | title = Serology, chemistry, and genetics of O and K antigens of ''Escherichia coli'' | journal = Bacteriological Reviews | volume = 41 | issue = 3 | pages = 667–710 | date = September 1977 | pmid = 334154 | pmc = 414020 | doi =  10.1128/MMBR.41.3.667-710.1977}}</ref> It is, however, common to cite only the [[serogroup]], i.e. the [[O antigen|O-antigen]]. At present, about 190 serogroups are known.<ref>{{cite journal | vauthors = Stenutz R, Weintraub A, Widmalm G | title = The structures of ''Escherichia coli'' O-polysaccharide antigens | journal = FEMS Microbiology Reviews | volume = 30 | issue = 3 | pages = 382–403 | date = May 2006 | pmid = 16594963 | doi = 10.1111/j.1574-6976.2006.00016.x | doi-access = free }}</ref> The common laboratory strain has a mutation that prevents the formation of an [[O antigen|O-antigen]] and is thus not typeable.

===Genome plasticity and evolution===
Like all lifeforms, new strains of ''E. coli'' [[evolution|evolve]] through the natural biological processes of [[mutation]], [[gene duplication]], and [[horizontal gene transfer]]; in particular, 18% of the genome of the [[Escherichia coli in molecular biology|laboratory strain MG1655]] was horizontally acquired since the divergence from ''[[Salmonella]]''.<ref name="pmid9689094">{{cite journal | vauthors = Lawrence JG, Ochman H | title = Molecular archaeology of the ''Escherichia coli'' genome | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 95 | issue = 16 | pages = 9413–17 | date = August 1998 | pmid = 9689094 | pmc = 21352 | doi = 10.1073/pnas.95.16.9413 | bibcode = 1998PNAS...95.9413L | doi-access = free }}</ref> [[E. coli K-12|''E. coli'' K-12]] and ''E. coli'' B strains are the most frequently used varieties for laboratory purposes. Some strains develop [[Trait (biology)|traits]] that can be harmful to a host animal. These [[Virulence|virulent]] strains typically cause a bout of [[diarrhea]] that is often [[Self-limiting (biology)|self-limiting]] in healthy adults but is frequently lethal to children in the developing world.<ref name=Nataro>{{cite journal | vauthors = Nataro JP, Kaper JB | title = Diarrheagenic ''Escherichia coli'' | journal = Clinical Microbiology Reviews | volume = 11 | issue = 1 | pages = 142–201 | date = January 1998 | pmid = 9457432 | pmc = 121379 | doi = 10.1128/CMR.11.1.142 }}</ref> More virulent strains, such as [[Escherichia coli O157:H7|O157:H7]], cause serious illness or death in the elderly, the very young, or the [[immunocompromised]].<ref name=Nataro/><ref name=Viljanen>{{cite journal | vauthors = Viljanen MK, Peltola T, Junnila SY, Olkkonen L, Järvinen H, Kuistila M, Huovinen P | s2cid = 23087850 | title = Outbreak of diarrhoea due to ''Escherichia coli'' O111:B4 in schoolchildren and adults: association of Vi antigen-like reactivity | journal = Lancet | volume = 336 | issue = 8719 | pages = 831–34 | date = October 1990 | pmid = 1976876 | doi = 10.1016/0140-6736(90)92337-H }}</ref>

The genera ''[[Escherichia]]'' and ''[[Salmonella]]'' diverged around 102&nbsp;million years ago (credibility interval: 57–176&nbsp;mya), an event unrelated to the much earlier (see ''[[Synapsid]]'') divergence of their hosts: the former being found in mammals and the latter in birds and reptiles.<ref name="pmid15535883">{{cite journal | vauthors = Battistuzzi FU, Feijao A, Hedges SB | title = A genomic timescale of prokaryote evolution: insights into the origin of methanogenesis, phototrophy, and the colonization of land | journal = BMC Evolutionary Biology | volume = 4 | pages = 44 | date = November 2004 | pmid = 15535883 | pmc = 533871 | doi = 10.1186/1471-2148-4-44 | doi-access = free }}</ref> This was followed by a split of an ''Escherichia'' ancestor into five species (''[[Escherichia albertii|E. albertii]]'', ''E. coli'', ''[[Escherichia fergusonii|E. fergusonii]]'', ''[[Escherichia hermannii|E. hermannii]]'', and ''[[Escherichia vulneris|E. vulneris]]'').<!--Dates unavailable--> The last ''E. coli'' ancestor split between 20 and 30&nbsp;million years ago.<ref name="pmid9866203">{{cite journal | vauthors = Lecointre G, Rachdi L, Darlu P, Denamur E | title = Escherichia coli molecular phylogeny using the incongruence length difference test | journal = Molecular Biology and Evolution | volume = 15 | issue = 12 | pages = 1685–95 | date = December 1998 | pmid = 9866203 | doi = 10.1093/oxfordjournals.molbev.a025895 | doi-access = free }}</ref>

The [[E. coli long-term evolution experiment|long-term evolution experiments using ''E. coli'']], begun by [[Richard Lenski]] in 1988, have allowed direct observation of genome evolution over more than 65,000 generations in the laboratory.<ref>{{cite web | vauthors = Holmes B | date = 9 June 2008 | url = https://www.newscientist.com/channel/life/dn14094-bacteria-make-major-evolutionary-shift-in-the-lab.html | title = Bacteria make major evolutionary shift in the lab | archive-url = https://web.archive.org/web/20080828030920/http://www.newscientist.com/channel/life/dn14094-bacteria-make-major-evolutionary-shift-in-the-lab.html | archive-date=28 August 2008 | work = New Scientist }}</ref> For instance, ''E. coli'' typically do not have the ability to grow aerobically with [[citrate]] as a [[carbon source (biology)|carbon source]], which is used as a diagnostic criterion with which to differentiate ''E. coli'' from other, closely, related bacteria such as ''Salmonella''. In this experiment, one population of ''E. coli'' unexpectedly evolved the ability to aerobically metabolize [[citrate]], a major evolutionary shift with some hallmarks of microbial [[speciation]].[[File:Scanning electron micrograph of an E. coli colony.jpg|thumb|Scanning electron micrograph of an ''E. coli'' colony]]

In the microbial world, a relationship of predation can be established similar to that observed in the animal world. Considered, it has been seen that ''E. coli'' is the prey of multiple generalist predators, such as ''[[Myxococcus xanthus]]''. In this predator-prey relationship, a parallel evolution of both species is observed through genomic and phenotypic modifications, in the case of ''E. coli'' the modifications are modified in two aspects involved in their virulence such as mucoid production (excessive production of exoplasmic acid alginate ) and the suppression of the [[OmpT]] gene, producing in future generations a better adaptation of one of the species that is counteracted by the evolution of the other, following a co-evolutionary model demonstrated by the [[Red Queen hypothesis]].<ref name="pmid31541093">{{cite journal | vauthors = Nair RR, Vasse M, Wielgoss S, Sun L, Yu YN, Velicer GJ | title = Bacterial predator-prey coevolution accelerates genome evolution and selects on virulence-associated prey defences | journal = Nature Communications | volume = 10 | issue = 1 | pages = 4301 | date = September 2019 | pmid = 31541093 | pmc = 6754418 | doi = 10.1038/s41467-019-12140-6 | bibcode = 2019NatCo..10.4301N }}</ref>

===Neotype strain===
''E. coli'' is the type species of the genus (''Escherichia'') and in turn ''Escherichia'' is the type genus of the family [[Enterobacteriaceae]], where the family name does not stem from the genus ''[[Enterobacter]]'' + "i" (sic.) + "[[Bacterial taxonomy|aceae]]", but from "enterobacterium" + "aceae" (enterobacterium being not a genus, but an alternative trivial name to enteric bacterium).<ref name=Bergey2B /><ref name="pmid9103655">{{cite journal | vauthors = Euzéby JP | title = List of Bacterial Names with Standing in Nomenclature: a folder available on the Internet | journal = International Journal of Systematic Bacteriology | volume = 47 | issue = 2 | pages = 590–2 | date = April 1997 | pmid = 9103655 | doi = 10.1099/00207713-47-2-590 | doi-access = free }}</ref><ref>{{cite journal |title=Conservation of the family name Enterobacteriaceae, of the name of the type genus, and designation of the type species |journal=International Bulletin of Bacteriological Nomenclature and Taxonomy |date=1 January 1958 |volume=8 |issue=1 |pages=73–74 |doi=10.1099/0096266X-8-1-73 |doi-access=free }}</ref>

The original strain described by Escherich is believed to be lost, consequently a new type strain (neotype) was chosen as a representative: the neotype strain is U5/41<sup>T</sup>,<ref name="Meier-Kolthoff14">{{cite journal | vauthors = Meier-Kolthoff JP, Hahnke RL, Petersen J, Scheuner C, Michael V, Fiebig A, Rohde C, Rohde M, Fartmann B, Goodwin LA, Chertkov O, Reddy T, Pati A, Ivanova NN, Markowitz V, Kyrpides NC, Woyke T, Göker M, Klenk HP | display-authors = 6 | title = Complete genome sequence of DSM 30083(T), the type strain (U5/41(T)) of ''Escherichia coli'', and a proposal for delineating subspecies in microbial taxonomy | journal = Standards in Genomic Sciences | volume = 9 | pages = 2 | year = 2013 | pmid = 25780495 | pmc = 4334874 | doi = 10.1186/1944-3277-9-2 | doi-access = free }}</ref> also known under the deposit names [[DSMZ|DSM 30083]],<ref>{{cite web|url=http://www.dsmz.de/catalogues/details/culture/DSM-30083.html|title=Details: DSM-30083|work=dsmz.de|access-date=10 January 2017}}</ref> [[American Type Culture Collection|ATCC 11775]],<ref>{{cite web|url=http://www.atcc.org/ATCCAdvancedCatalogSearch/ProductDetails/tabid/452/Default.aspx?ATCCNum=11775&Template=bacteria|title=Escherichia coli (Migula) Castellani and Chalmers ATCC 11775&tra|work=atcc.org|access-date=10 January 2017|archive-date=4 December 2012|archive-url=https://web.archive.org/web/20121204005421/http://www.atcc.org/ATCCAdvancedCatalogSearch/ProductDetails/tabid/452/Default.aspx?ATCCNum=11775&Template=bacteria|url-status=dead}}</ref> and NCTC 9001,<ref>{{cite web|url=https://lpsn.dsmz.de/genus/escherichia|title=Escherichia|publisher=LPSN|access-date=6 February 2011}}</ref> which is pathogenic to chickens and has an O1:K1:H7 [[serotype]].<ref>{{cite web|url=http://www.jcm.riken.go.jp/cgi-bin/jcm/jcm_number?JCM=1649 |title=Escherichia coli (Migula 1895) Castellani and Chalmers 1919 |work=JCM Catalogue }}</ref> However, in most studies, either [[O157:H7]], K-12 MG1655, or K-12 W3110 were used as a representative ''E. coli''. The genome of the type strain has only lately (2013) been sequenced.<ref name="Meier-Kolthoff14"/>

===Phylogeny of ''E. coli'' strains===
{{Update|section|inaccurate=yes|reason=Cladogram uses an [[WP:OR|OR]] extension of Sims & Kim 2011, which is outdated anyways and should be replaced by Meier-Kolthoff et al. 2014 (fig 6).|talk=Phylogeny|date=January 2021}}
Many strains belonging to this species have been isolated and characterised. In addition to serotype (''vide supra''), they can be classified according to their [[phylogeny]], i.e. the inferred evolutionary history, as shown below where the species is divided into six groups as of 2014.<ref name="comparison02">{{cite journal | vauthors = Sims GE, Kim SH | title = Whole-genome phylogeny of ''Escherichia coli/Shigella'' group by feature frequency profiles (FFPs) | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 108 | issue = 20 | pages = 8329–34 | date = May 2011 | pmid = 21536867 | pmc = 3100984 | doi = 10.1073/pnas.1105168108 | bibcode = 2011PNAS..108.8329S | doi-access = free }}</ref><ref name="pmid21713444">{{cite journal | vauthors = Brzuszkiewicz E, Thürmer A, Schuldes J, Leimbach A, Liesegang H, Meyer FD, Boelter J, Petersen H, Gottschalk G, Daniel R | display-authors = 6 | title = Genome sequence analyses of two isolates from the recent ''Escherichia coli'' outbreak in Germany reveal the emergence of a new pathotype: Entero-Aggregative-Haemorrhagic ''Escherichia coli'' (EAHEC) | journal = Archives of Microbiology | volume = 193 | issue = 12 | pages = 883–91 | date = December 2011 | pmid = 21713444 | pmc = 3219860 | doi = 10.1007/s00203-011-0725-6 | bibcode = 2011ArMic.193..883B }}</ref> Particularly the use of [[Whole genome sequencing|whole genome sequences]] yields highly supported phylogenies.<ref name="Meier-Kolthoff14" /> The [[phylogroup]] structure remains robust to newer methods and sequences, which sometimes adds newer groups, giving 8 or 14 as of 2023.<ref>{{cite journal | vauthors = Koh XP, Shen Z, Woo CF, Yu Y, Lun HI, Cheung SW, Kwan JK, Lau SC | display-authors = 6 | title = Genetic and Ecological Diversity of ''Escherichia coli'' and Cryptic ''Escherichia'' Clades in Subtropical Aquatic Environments | journal = Frontiers in Microbiology | volume = 13 | pages = 811755 | date = 2022 | pmid = 35250929 | pmc = 8891540 | doi = 10.3389/fmicb.2022.811755 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Abram K, Udaondo Z, Bleker C, Wanchai V, Wassenaar TM, Robeson MS, Ussery DW | title = Mash-based analyses of Escherichia coli genomes reveal 14 distinct phylogroups | journal = Communications Biology | volume = 4 | issue = 1 | pages = 117 | date = January 2021 | pmid = 33500552 | pmc = 7838162 | doi = 10.1038/s42003-020-01626-5 }}</ref>

The link between phylogenetic distance ("relatedness") and pathology is small,<ref name="Meier-Kolthoff14" /> ''e.g.'' the [[O157:H7]] serotype strains, which form a [[clade]] ("an exclusive group")—group E below—are all enterohaemorragic strains (EHEC), but not all EHEC strains are closely related. In fact, four different species of ''Shigella'' are nested among ''E. coli'' strains (''vide supra''), while ''[[Escherichia albertii|E. albertii]]'' and ''[[Escherichia fergusonii|E. fergusonii]]'' are outside this group. Indeed, all ''Shigella'' species were placed within a single subspecies of ''E. coli'' in a phylogenomic study that included the type strain.<ref name="Meier-Kolthoff14" /> All commonly used [[Escherichia coli (molecular biology)|research strains]] of ''E. coli'' belong to group A and are derived mainly from Clifton's K-12 strain (λ<sup>+</sup> F<sup>+</sup>; O16) and to a lesser degree from [[Félix d'Herelle|d'Herelle]]'s "[[Bacillus coli]]" strain (B strain; O7).

There have been multiple proposals to revise the taxonomy to match phylogeny.<ref name="Meier-Kolthoff14" /> However, all these proposals need to face the fact that ''Shigella'' remains a widely used name in medicine and find ways to reduce any confusion that can stem from renaming.<ref>{{cite journal |vauthors = Cobo-Simón M, Hart R, Ochman H |title = Escherichia Coli: What Is and Which Are? |journal = Molecular Biology and Evolution |volume = 40 |issue = 1 |pages = msac273 |date = January 2023 |pmid = 36585846 |pmc = 9830988 |doi = 10.1093/molbev/msac273 }}</ref>

{{clade|style=font-size:80%;line-height:80%
 |1=''[[Salmonella enterica]]''
 |2={{clade
  |1=[[Escherichia albertii|''E. albertii'']]
  |2={{clade
   |1=[[Escherichia fergusonii|''E. fergusonii'']]
   |2={{clade
     |1={{clade
      |label1=Group&nbsp;B2
      |1={{clade
       |1=[[E. coli SE15|''E. coli'' SE15]] (O150:H5. Commensal)
       |2=[[E. coli E2348/69|''E. coli'' E2348/69]] (O127:H6. Enteropathogenic)
      }}
     |2={{clade
      |1=[[E. coli ED1a|''E. coli'' ED1a]] O81 (Commensal)
      |2={{clade
       |1={{clade
        |1=[[E. coli CFT083|''E. coli'' CFT083]] (O6:K2:H1. UPEC)
        |2={{clade
         |1=[[E. coli APEC O1|''E. coli'' APEC O1]] (O1:K12:H7. APEC
         |2=[[E. coli UTI89|''E. coli'' UTI89]] O18:K1:H7. UPEC)
         |3=[[E. coli S88|''E. coli'' S88]]  (O45:K1. Extracellular pathogenic)
         }}
        }}
       |2={{clade
        |1=[[E. coli F11|''E. coli'' F11]]
        |2=[[E. coli 536|''E. coli'' 536]]
        }}
       }}
      }}
    |3={{clade
     |label1=Group&nbsp;D
     |1={{clade
      |1=[[E. coli UMN026|''E. coli'' UMN026]] (O17:K52:H18. Extracellular pathogenic)
      |2={{clade
       |1=[[E. coli SMS-3-5|''E. coli'']] (O19:H34. Extracellular pathogenic)
       |2=[[E. coli IAI39|''E. coli'']] (O7:K1. Extracellular pathogenic)
       }}
      }}
     |2={{clade
      |label1=Group&nbsp;E
      |1={{clade
       |1={{clade
        |1=[[E. coli EDL933|''E. coli'' EDL933]] (O157:H7  EHEC)
        |2=[[E. coli Sakai|''E. coli'' Sakai]] (O157:H7 EHEC)
        }}
       |2={{clade
        |1=[[E. coli EC4115|''E. coli'' EC4115]] (O157:H7 EHEC)
        |2=[[E. coli TW14359|''E. coli'' TW14359]] (O157:H7 EHEC)
        }}
       }}
      |2={{clade
       |label1=Shigella
       |1={{clade
        |1={{clade
         |1=''[[Shigella dysenteriae]]''
         |2={{clade
          |1=''[[Shigella sonnei]]''
          |2={{clade
           |1=''[[Shigella boydii]]''
           |2=''[[Shigella flexneri]]''
           }}
          }}
         }}
        }}
       |2={{clade
        |label1=Group&nbsp;B1
        |1={{clade
         |1={{clade
          |1=[[E. coli E24377A|''E. coli'' E24377A]] (O139:H28. Enterotoxigenic)
          |2={{clade
           |1={{clade
            |1={{clade
             |1=[[E. coli E110019|''E. coli'' E110019]] <!-- what is this? -->
             |2={{clade
              |1=[[E. coli 11368|''E. coli'' 11368]] (O26:H11. EHEC)
              |2=[[E. coli 11128|''E. coli'' 11128]] (O111:H-. EHEC)
              }}
             }}
            |2={{clade
             |1={{clade
              |1=[[E. coli IAI1|''E. coli'' IAI1]] O8 (Commensal)
              |2=[[E. coli 53638|''E. coli'' 53638]] (EIEC)
              }}
             |2={{clade
              |1=[[E. coli SE11|''E. coli'' SE11]] (O152:H28. Commensal)
              |2=[[E. coli B7A|''E. coli'' B7A]]
              }}
             }}
            }}
           |2={{clade
            |1={{clade
             |1={{clade
              |1=[[E. coli 12009|''E. coli'' 12009]] (O103:H2. EHEC)
              |2=[[E. coli O104:H4|''E. coli'' GOS1]] (O104:H4 EAHEC) German 2011 outbreak
              }}
             |2=[[E. coli E22|''E. coli'' E22]]
             }}
            |2={{clade
             |1=[[E. coli Oslo O103|''E. coli'' Oslo O103]]
             |2=[[E. coli 55989|''E. coli'' 55989]] (O128:H2. Enteroaggressive)
             }}
            }}
           }}
          }}
         }}
        |label2=Group&nbsp;A
        |2={{clade
         |1={{clade
          |1=[[E. coli HS|''E. coli'' HS]] (O9:H4. Commensal)
          |2=[[E. coli ATCC8739|''E. coli'' ATCC8739]] (O146. Crook's E.coli used in phage work in the 1950s)
          }}
         |2={{clade
          |label1=K-12 strain derivatives
          |1={{clade
           |1=[[E. coli K-12 W3110|''E. coli'' K-12 W3110]] (O16. λ<sup>−</sup> F<sup>−</sup> "wild type" molecular biology strain)
           |2=[[E. coli K-12 DH10b|''E. coli'' K-12 DH10b]] (O16. high electrocompetency molecular biology strain)
           |3=[[E. coli K-12 DH1|''E. coli'' K-12 DH1]]  (O16. high chemical competency molecular biology strain)
           |4=[[E. coli K-12 MG1655|''E. coli'' K-12 MG1655]] (O16. λ<sup>−</sup> F<sup>−</sup> "wild type" molecular biology strain)
           |5=[[E. coli BW2952|''E. coli'' BW2952]] (O16. competent molecular biology strain)
           }}
          |2={{clade
            |1=[[E. coli 101-1|''E. coli'' 101-1]] (O? H?. EAEC)
            |label2=B strain derivatives
            |2={{clade
             |1=[[E. coli B REL606|''E. coli'' B REL606]] (O7. high competency molecular biology strain)
             |2=[[E. coli BL21-DE3|''E. coli'' BL21-DE3]] (O7. expression molecular biology strain with T7 polymerase for pET system)
            }}
           }}
          }}
         }}
        }}
       }}
      }}
     }}
    }}
   }}
  }}
 }}
}}