Escherichia

Abstract Esch.er.i'chi.a. M.L. fem. n. Escherichia named after Theodor Escherich, who isolated the type species of the genus. Straight cylindrical rods, 1.1–1.5 × 2.0–6.0 µm, occurring singly or in pairs. Conform to the general definition of the family Enterobacteriaceae . Gram negative. Motile by peritrichous flagella or nonmotile. Aerobic and facultatively anaerobic having both a respiratory and a fermentative type of metabolism, but anaerogenic biotypes occur. Oxidase negative. Chemoorganotrophic. Both acid and gas are formed from most fermentable carbohydrates, but i ‐inositol is not utilized and D ‐adonitol is utilized only by Escherichia fergusonii . Lactose is fermented by most strains of Escherichia coli , but fermentation may be delayed or absent in Escherichia blattae, Escherichia hermannii, Escherichia fergusonii , and Escherichia vulneris . Do not grow in KCN ( with the exception of E . hermannii and a small proportion of E . vulneris ). Usually do not produce H 2 S . E . coli occur naturally in the lower part of the intestine of warm‐blooded animals, E . blattae in the hind‐gut of cockroaches, and E . fergusonii, E . hermannii , and E . vulneris are found in the intestine, as well as extraintestinal sites of warm‐blooded animals. Seven copies of the rrn operon with genes coding for 16S, 23S, and 5S rRNA are present on the chromosome of E . coli . Comparative sequence analysis between the genes for 16S rRNA of E . coli, E . vulneris , and E . hermannii and homologous genes from all eubacteria places E . coli and E . vulneris together in a tightly related cluster with shigellae, and E . hermannii between Salmonella spp. and Citrobacter freundii (Cilia et al., 1996). Based on 16S rRNA sequencing, escherichiae belong in the Gammaproteobacteria . The mol % G + C of the DNA is : 48–59. Type species : Escherichia coli (Migula 1895) Castellani and Chalmers 1919, 941 ( Bacillus coli Migula 1895, 27.) Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Escherichia is: correct name (last update, February 2025) * . LPSN classification: Bacteria / Pseudomonadati / Pseudomonadota / Gammaproteobacteria / Enterobacterales / Enterobacteriaceae / Escherichia The genus Escherichia can also be recovered in the Genome Taxonomy Database (GTDB) as g__Escherichia (version v220) ** . GTDB classification: d__Bacteria / p__Pseudomonadota /