Escherichia

Escherichia is a genus of Gram-negative, rod-shaped bacteria in the family Enterobacteriaceae. Members are typically facultatively anaerobic and may be motile with peritrichous flagella, though some species are non-motile. The genus contains numerous species, of which the best known is Escherichia coli (E. coli), a normal inhabitant of the intestinal microbiota of humans and warm-blooded animals and a frequent cause of disease when displaced. The genus lies within the Gammaproteobacteria, order Enterobacterales, class Gammaproteobacteria, phylum Proteobacteria.

Most Escherichia species are commensals in the intestinal tract; some environmental species are found in water and soil. Pathogenic members include several diarrheagenic E. coli pathotypes (ETEC, EPEC, EHEC, EAEC) that cause gastroenteritis, while extraintestinal pathogenic E. coli (ExPEC) strains cause urinary tract infections, neonatal meningitis, and sepsis. Transmission is primarily fecal-oral, with outbreaks linked to contaminated food and water.

In the laboratory, E. coli strains such as K-12 are widely used as model organisms and vectors for recombinant DNA studies. The genus is named after Theodor Escherich, who first described E. coli in 1885. Escherichia remains a key focus in microbiology due to its ecological ubiquity, medical relevance, and role as a model organism in genetics and molecular biology.