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JC 發問時間: 社會與文化語言 · 1 0 年前

Gram-positive & Gram-negative

Q: What are the differences between the cells walls of Gram-positive and Gram-gative bacteria that

might explain differences in the rate of decoloriztion?

已更新項目:

I didn't intend to ask for any translation help, but thanks for your good response though.

Can anyone help me to provide a solution for my problem I asked?

2 個解答

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  • Dana
    Lv 4
    1 0 年前
    最佳解答

    are you asking for translation or answers?

    2006-01-29 15:12:20 補充:

    *** Read the underlined and highlighted parts and my summary   The cell walls for gram-negative microorganisms have a higher lipid content than gram-positive cells. Originally, both kinds of cells are penetrated by the crystal violet. Iodine is subsequently added as a mordant to form the crystal violet-iodine complex so that the dye cannot be removed too easily. This step is commonly referred to as fixing the dye. However, the subsequent treatment with the decolorizer, which is a mixed solvent of ethanol and acetone, dissolves the lipid layer from the gram-negative cells. The removal of the lipid layer enhances the leaching of the primary stain from the cells into the surrounding solvent. In contrast, the solvent dehydrates the thicker gram-positive cell wall, closing the pores as the cell wall shrinks during dehydration. As a result, the the diffusion of the stain-iodine complex out from the cell is obstructed, and the cells remain stained.  At any rate, if the decolorizer treatment is properly timed, there exists a period during which the crystal violet-iodine complex is effectively removed from the gram-negative cells but still retained in the gram-positive ones. Thus, the length of the decolorizer treatment is critical in clearly differentiating the gram-positive cells from the gram-negative cells. A prolonged exposure to the decolorizing agent will remove all the stain from both types of cells. (www.glue.umd.edu/~NSW/ench485/lab9b.htm)-----------------------------------------------------------------------------------------Summarygram stain procedures: 1) Add crystal violet -> all bacteria stain purple2) Add Idodine to form the stable crystal violet-iodine complex  -> remain purple3) Decolorize with alcohol -> G+ purple ; G- colorlessfor gram-ve : their thin layer of peptidoglycan is covered by an outer lipid membrane composed of lipoprotein and lipopolysaccharide. And since their peptidoglycan is relatively thin, the crystal violet-iodine complex is easily washed out during decolorization, causing a faster rate of decolorization than the gram+ve.

    參考資料: (www.glue.umd.edu/~NSW/ench485/lab9b.htm)
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  • 1 0 年前

    What are the differences between the cells walls of Gram-positive and Gram-gative bacteria that might explain differences in the rate of decoloriztion? 可解釋染色程度的差異性之葛蘭氏陽性菌和葛蘭氏陰性菌細胞壁的差異為何?

    參考資料: 自己
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