Editing DNA–DNA hybridization (section)

===In microbiology===
DNA–DNA hybridization (DDH) is used as a primary method to distinguish bacterial species as it is difficult to visually classify them accurately.<ref>{{Cite journal |last1=Auch |first1=Alexander F. |last2=von Jan |first2=Mathias |last3=Klenk |first3=Hans-Peter |last4=Göker |first4=Markus |year=2010 |title=Digital DNA-DNA hybridization for microbial species delineation by means of genome-to-genome sequence comparison |journal=Standards in Genomic Sciences |language=en |volume=2 |issue=1 |pages=117–134 |doi=10.4056/sigs.531120 |issn=1944-3277 |pmc=3035253 |pmid=21304684}}</ref> This technique is not widely used on larger organisms where differences in species are easier to identify. In the late 1900s, strains were considered to belong to the same species if they had a DNA–DNA similarity value greater than 70% and their melting temperatures were within 5&nbsp;°C of each other.<ref name="Brenner1979">{{cite journal|author = Brenner DJ|title=Deoxyribonucleic acid reassociation in the taxonomy of enteric bacteria|journal=International Journal of Systematic Bacteriology|volume=23|issue=4|pages=298–307|year=1973|doi=10.1099/00207713-23-4-298|doi-access=free}}</ref><ref name="Wayne1987">{{cite journal|vauthors = Wayne LG, Brenner DJ, Colwell RR, Grimont PD, Kandler O, Krichevsky MI, Moore LH, ((Moore WEC)), ((Murray RGE)), Stackebrandt E, Starr MP, Trüper HG|year = 1987|title = Report of the ad hoc committee on reconciliation of approaches to bacterial systematics|journal = International Journal of Systematic Bacteriology|volume = 37|issue = 4|pages = 463–464|doi = 10.1099/00207713-37-4-463|doi-access = free}}</ref><ref name="Tindall2010">{{cite journal|vauthors = Tindall BJ, Rossello-Mora R, ((Busse H-J)), Ludwig W, Kampfer P|title = Notes on the characterization of prokaryote strains for taxonomic purposes|journal = International Journal of Systematic and Evolutionary Microbiology|volume = 60|issue = Pt 1|pages = 249–266|doi = 10.1099/ijs.0.016949-0|pmid = 19700448|year = 2010|doi-access = free|hdl = 10261/49238|hdl-access = free}}</ref> In 2014, a threshold of 79% similarity has been suggested to separate bacterial subspecies.<ref name="doi:10.1186/1944-3277-9-2">{{cite journal|vauthors = Meier-Kolthoff JP, Hahnke RL, Petersen JP, Scheuner CS, Michael VM, Fiebig AF, Rohde CR, Rohde MR, Fartmann BF, Goodwin LA, Chertkov OC, Reddy TR, Pati AP, Ivanova NN, Markowitz VM, Kyrpides NC, Woyke TW, Klenk HP, Göker M|title=Complete genome sequence of DSM 30083<sup>T</sup>, the type strain (U5/41<sup>T</sup>) of ''Escherichia coli'', and a proposal for delineating subspecies in microbial taxonomy|journal=Standards in Genomic Sciences|volume=9|pages=2|year=2013|doi=10.1186/1944-3277-9-2|pmid=25780495|pmc=4334874 |doi-access=free }}</ref> 

DDH is a common technique for bacteria, but it is labor intensive, error-prone, and technically challenging. In 2004, a new DDH technique was described. This technique utilized microplates and colorimetrically labelled DNA to decrease the time needed and increase the amount of samples that can be processed.<ref>{{Cite journal|last1=Mehlen|first1=André|last2=Goeldner|first2=Marcia|last3=Ried|first3=Sabine|last4=Stindl|first4=Sibylle|last5=Ludwig|first5=Wolfgang|last6=Schleifer|first6=Karl-Heinz|date=November 2004|title=Development of a fast DNA-DNA hybridization method based on melting profiles in microplates|journal=Systematic and Applied Microbiology|volume=27|issue=6|pages=689–695|doi=10.1078/0723202042369875|issn=0723-2020|pmid=15612626}}</ref> This new DDH technique became the standard for bacterial taxonomy.<ref>{{Cite journal |last1=Huang |first1=Chien-Hsun |last2=Li |first2=Shiao-Wen |last3=Huang |first3=Lina |last4=Watanabe |first4=Koichi |date=2018 |title=Identification and Classification for the Lactobacillus casei Group |journal=Frontiers in Microbiology |volume=9 |page=1974 |doi=10.3389/fmicb.2018.01974 |issn=1664-302X |pmc=6113361 |pmid=30186277|doi-access=free }}</ref>