The reason for conducting this experiment was to determine and identify a given unknown bacteria and to understand how to recognize the variance between the several types of Gram-negative bacteria. The given Gram-negative bacteria would be classified as one of the following microorganisms: Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa or Salmonella typhimurium. To confirm the Gram-negative properties of the bacteria a Gram Stain procedure was carried out and to distinguish our given unknown from the remaining five bacteria, a variety of thoroughly run tests were conducted to ensure accuracy and precision. A T Streak plate was created from the unknown bacteria and then used in the
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A Gram stain not only distinguishes between positive and negative but it also gives reputable classification in morphology, size and arrangement. Gram- negative bacteria and Gram- positive bacteria are both stained using the exact same method but G- bacteria will present itself as a red or pink color while G+ bacterial will appear purple. The Gram Stain procedure vitalizes the following 4 components: Crystal Violet, which is used as the primary stain; Gram’s Iodine, which is used as a mordant to enhance and fix the crystal violet stain; A Decolorizer, that is made up of a mixture of alcohol and acetone which allows the lipid to be removed from the cell wall making it more porous and unable to retain the crystal violet (Leboffe & Pierce, 196); Safranin, is used as the counterstain which reinstates color to the decolorized G- bacteria, causing the reddish-pink pigment. The difference in color is based on the difference in wall formation between the two bacteria. Gram Negative bacteria have a thin cell wall (8-12 nm) with high lipoprotein/lipopolysaccharide content, a thin, single layer of peptidoglycan and the presence of a perplasmic space and porins (Aryal). Gram Positive bacteria have a thick cell wall in comparison to G- bacteria (20-30 nm) with little to no lipoprotein/lipopolysaccharide content with …show more content…
The MR test assess for mixed acid production from glucose fermentation, which overcomes the phosphate buffer and lowers the pH. The MR test is also noted to produce stable acid end products. The peptone and glucose from the broth supply protein and fermentable carbohydrate while the potassium phosphate resists pH changes in the medium. To confirm mixed acid fermentation a methyl red indicator is added to the broth after a sufficient incubation time of 24 hours. Methyl red is red at pH 4.4 and yellow at pH of 6.2 and assorted shades of orange in between. A red result indicates that the bacteria are positive for mixed acid fermentation; no color change (yellow) or an orange result is either negative or inconclusive, neither of which are positive for mixed acids (Leboffe & Pierce,
A Gram stain not only distinguishes between positive and negative but it also gives reputable classification in morphology, size and arrangement. Gram- negative bacteria and Gram- positive bacteria are both stained using the exact same method but G- bacteria will present itself as a red or pink color while G+ bacterial will appear purple. The Gram Stain procedure vitalizes the following 4 components: Crystal Violet, which is used as the primary stain; Gram’s Iodine, which is used as a mordant to enhance and fix the crystal violet stain; A Decolorizer, that is made up of a mixture of alcohol and acetone which allows the lipid to be removed from the cell wall making it more porous and unable to retain the crystal violet (Leboffe & Pierce, 196); Safranin, is used as the counterstain which reinstates color to the decolorized G- bacteria, causing the reddish-pink pigment. The difference in color is based on the difference in wall formation between the two bacteria. Gram Negative bacteria have a thin cell wall (8-12 nm) with high lipoprotein/lipopolysaccharide content, a thin, single layer of peptidoglycan and the presence of a perplasmic space and porins (Aryal). Gram Positive bacteria have a thick cell wall in comparison to G- bacteria (20-30 nm) with little to no lipoprotein/lipopolysaccharide content with …show more content…
The MR test assess for mixed acid production from glucose fermentation, which overcomes the phosphate buffer and lowers the pH. The MR test is also noted to produce stable acid end products. The peptone and glucose from the broth supply protein and fermentable carbohydrate while the potassium phosphate resists pH changes in the medium. To confirm mixed acid fermentation a methyl red indicator is added to the broth after a sufficient incubation time of 24 hours. Methyl red is red at pH 4.4 and yellow at pH of 6.2 and assorted shades of orange in between. A red result indicates that the bacteria are positive for mixed acid fermentation; no color change (yellow) or an orange result is either negative or inconclusive, neither of which are positive for mixed acids (Leboffe & Pierce,