|
( Escherichia coli)
Escherichia coli (pronounced /????'r?ki? 'ko?la?/) (E. coli), is a bacterium that is commonly found in the lower intestine of warm-blooded animals. Most E. coli strains are harmless, but some, such as serotype O157H7, can cause serious food poisoning in humans, and are occasionally responsible for costly product recalls.[1][2] The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2,[3] or by preventing the establishment of pathogenic bacteria within the intestine.[4][5] A strain of E. coli is a sub-group within the species that has unique characteristics that distinguish it from other E. coli strains. These differences are often detectable only on the molecular level; however, they may result in changes to the physiology or lifecycle of the bacterium. For example, a strain may gain pathogenic capacity, the ability to use a unique carbon source, the ability to inhabit a particular ecological niche or the ability to resist antimicrobial agents. Different strains of E. coli are often host-specific, making it possible to determine the source of fecal contamination in environmental samples.[citation needed] Depending on which E. coli strains are present in a water sample, for example, assumptions can be made about whether the contamination originated from a human, other mammal or bird source. New strains of E. coli evolve through the natural biological process of mutation, and some strains develop traits that can be harmful to a host animal. Although virulent strains typically cause no more than a bout of diarrhea in healthy adult humans, particularly virulent strains, such as O157H7 or O111B4, can cause serious illness or death in the elderly, the very young or the immunocompromised.[4] Optimal growth of E. coli occurs at 37°C, but some laboratory strains can multiply at temperatures of up to 49°C.[10] Growth can be driven by aerobic or anaerobic respiration, using a large variety of redox pairs, including the oxidation of pyruvic acid, formic acid, hydrogen and amino acids, and the reduction of substrates such as oxygen, nitrate, dimethyl sulfoxide and trimethylamine N-oxide.[11]
|
