Eosin Methylene Blue Agar Gram Stain

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The Gram stain is considered one of the most important stains because allows researchers to distinguish between the Gram-positive bacteria and the Gram-negative bacteria. The results show the differences between the cells walls of the bacteria. The Phenylethyl Alcohol Agar is a selected media that allows the growth of a Gram-negative bacteria while inhibiting the DNA synthesis of Gram Negative bacteria. The Eosin Methylene Blue Agar which contains Peptone, lactose, sucrose and the dyes eosin Y and Methylene blue. These are the sugars that are fermentable by the fecal coliforms, which are the gram negative facultative anaerobic rods. The Gram-positive bacteria is restricted or held back by the dyes. Vigorous lactose or sucrose fermenters will produce bright metallic green colonies on the plate. …show more content…
PR Fermentation broths are based on Phenol Red as pH indicators. There are various carbohydrates that are incorporated in the base to serve as a substrate and these are Glucose, Sucrose, and Lactose. The Kligler Iron test is a multiple test media that will detect fermentation of lactose or glucose and will also indicated the production of hydrogen sulfide that may occur. Sulfur reduction (H2S) may be produced from the putrefaction of cysteine or by the anaerobic respiration. If the butt of the tube is yellow will indicate that glucose was fermented and it turns a phenol red yellow. If the whole tube is yellow this indicates that both glucose and lactose are fermented. The Citrate test which tests the ability of the organism to use the citrate as a carbon source. A change in pH indicates that the organism could use citrate in the Krebs cycle and the aerobic respiration. If the broth turns blue the citrate is positive. If there was no color change, the organism is citrate is
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