DescriptionLactose fementing (LF), and non-lactose fermenting (NLF) colonies on MacConkey agar.jpg
English: MacConkey agar is a selective and differential medium used to isolate and differentiate Gram-negative bacteria, particularly those belonging to the family Enterobacteriaceae. It's primarily used to distinguish between lactose-fermenting (LF) and non-lactose-fermenting (NLF) colonies. Here's what you can typically observe on MacConkey agar: Lactose-Fermenting (LF) Colonies- Appearance: LF colonies appear pink to deep red on MacConkey agar. Explanation: LF bacteria possess the enzyme β-galactosidase, which allows them to ferment lactose present in the medium. The fermentation of lactose produces acid, which lowers the pH of the agar. The pH change triggers a color change of the pH indicator (neutral red), turning the colonies pink or red.Examples of LF Bacteria: Common LF bacteria include Escherichia coli, Klebsiella pneumoniae, and Enterobacter aerogenes.
Non-Lactose-Fermenting (NLF) Colonies: Appearance- NLF colonies appear colorless or pale on MacConkey agar. Explanation: NLF bacteria do not possess the necessary enzymes to ferment lactose. As a result, they do not produce acid during lactose fermentation, and the agar remains its natural color (colorless or pale). Examples of NLF Bacteria: Common NLF bacteria include Salmonella species, Shigella species, and Pseudomonas aeruginosa. These bacteria can grow on MacConkey agar but do not produce the characteristic pink or red color associated with lactose fermentation.
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.