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Non-pathogenic strains of E. coli ferment sorbitol to produce acid: Pathogenic E. coli cannot ferment sorbitol, so this strain uses peptone to grow. This raises the pH of the medium, allowing the pathogenic strain to be differentiated from other non-pathogenic E.coli strains through the action of the pH indicator in the medium.
TSI agar slant results: (from left) preinoculated (as control), P. aeruginosa, E. coli, Salmonella Typhimurium, Shigella flexneri The Triple Sugar Iron (TSI) test is a microbiological test roughly named for its ability to test a microorganism's ability to ferment sugars and to produce hydrogen sulfide. [1]
The organism on the right produced no color, so it does not appear to be a lactose fermenter. MacConkey agar is a selective and differential culture medium for bacteria. It is designed to selectively isolate gram-negative and enteric (normally found in the intestinal tract) bacteria and differentiate them based on lactose fermentation. [1]
E. coli use fermentation pathways as a final option for energy metabolism, as they produce very little energy in comparison to respiration. [7] Mixed acid fermentation in E. coli occurs in two stages. These stages are outlined by the biological database for E. coli, EcoCyc. [1] The first of these two stages is a glycolysis reaction.
Other enterobacteria such as E. coli will ferment the lactose present in the medium to an extent that will prevent pH reversion by decarboxylation and acidify the medium, turning it yellow. Salmonella species: red colonies, some with black centers. The agar itself will turn red due to the presence of Salmonella type colonies.
Lysogeny broth is used to culture Escherichia coli. [10] MacConkey agar is a selective and differential medium used to differentiate between gram-negative bacteria while inhibiting the growth of gram-positive bacteria. Adding bile salts and crystal violet to the agar inhibits the growth of most gram-positive bacteria, making MacConkey agar ...
Escherichia coli (E. coli) can be distinguished from most other coliforms by its ability to ferment lactose at 44 °C in the fecal coliform test, and by its growth and color reaction on certain types of culture media. When cultured on an eosin methylene blue (EMB) plate, a positive result for E. coli is metallic green colonies on a dark purple ...
Hektoen enteric agar (HEK, HE or HEA) is a selective and differential agar [1] primarily used to recover Salmonella and Shigella from patient specimens. HEA contains indicators of lactose fermentation and hydrogen sulfide production; as well as inhibitors to prevent the growth of Gram-positive bacteria.