Catherine Cutter Pennsylvania State University

Publish Date: May 3, 2012

Escherichia coli, better known as E. coli, is a Gram-negative, rod shaped bacterium. It is a facultative anaerobe with an optimum growth temperature of 37°C (98.6°F), but is known to grow at temperatures as high as 49°C. Some strains of E. coli possess flagella, and are therefore, motile. E. coli encompass a wide range of bacteria that display diverse characteristics. Therefore, subdivisions are made to better distinguish this group of bacteria based on similar characteristics. Subdivisions of E. coli are called serotypes and are classified as such, based on two surface antigens. The O-antigen is found on the surface of the lipopolysaccharide layer of Gram- negative bacteria, while the H-antigen is a flagellar-surface antigen. The different groups of E. coli are often referred to by their O-group identification. Examples include E. coli O26 or O145.