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Escherichia coli with pili                            E. coli colonies on TSA

What you should know:

Escherichia are Gram - negative rods, approx. 1 x 2 um in size, commonly found in the intestinal tracts of warm-blooded animals. Most strains are harmless or beneficial, but several are considered to be enteropathogenic, including the infamous E. coli O157:H7. Escherichia are chemoheterotrophic and facultative anaerobes, capable of fermenting a variety of sugars. Escherichia are members of the Enterobacteria and closely related to Proteus, Klebsiella, and Citrobacter.


 Domain Bacteria

    Phylum Proteobacteria 

        Class γ - Proteobacteria 

            Family Enterobacteriaceae

Bergey's Manual Volume 2: The Proteobacteria


Type species

Escherichia coli

Facultative anaerobe: oxidase-negative, catalase-positive, nitrate-positive

Metabolism: respiratory and fermentative , Acid/Gas from glucose and lactose, MR-positive, VP-negative

Other tests: indole-positive, citrate-negative, H2S-negative

Hydrolysis: amylase-negative, some strains casease-positive, DNAse-negative,, gelatinase-negative

Structure: some strains (K12) motile