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  2. Gram stain - Wikipedia

    en.wikipedia.org/wiki/Gram_stain

    Purple-stained gram-positive (left) and pink-stained gram-negative (right) Gram-positive bacteria have a thick mesh-like cell wall made of peptidoglycan (50–90% of cell envelope), and as a result are stained purple by crystal violet, whereas gram-negative bacteria have a thinner layer (10% of cell envelope), so do not retain the purple stain ...

  3. Purple bacteria - Wikipedia

    en.wikipedia.org/wiki/Purple_bacteria

    Purple bacteria or purple photosynthetic bacteria are Gram-negative proteobacteria that are phototrophic, capable of producing their own food via photosynthesis. [1] They are pigmented with bacteriochlorophyll a or b , together with various carotenoids , which give them colours ranging between purple, red, brown, and orange.

  4. Gram-negative bacteria - Wikipedia

    en.wikipedia.org/wiki/Gram-negative_bacteria

    Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. [1] Their defining characteristic is their cell envelope , which consists of a thin peptidoglycan cell wall sandwiched between an inner ( cytoplasmic ) membrane and an ...

  5. Bacterial cellular morphologies - Wikipedia

    en.wikipedia.org/wiki/Bacterial_cellular...

    Aggregatibacter actinomycetemcomitans is a Gram-negative coccobacillus prevalent in subgingival plaques. Acinetobacter strains may grow on solid media as coccobacilli. Bordetella pertussis is a Gram-negative coccobacillus responsible for causing whooping cough. Yersinia pestis, the bacterium that causes plague, is also coccobacillus. [26]

  6. Gram-positive bacteria - Wikipedia

    en.wikipedia.org/wiki/Gram-positive_bacteria

    Also, only some species are flagellates, and when they do have flagella, have only two basal body rings to support them, whereas gram-negative have four. Both gram-positive and gram-negative bacteria commonly have a surface layer called an S-layer. In gram-positive bacteria, the S-layer is attached to the peptidoglycan layer. Gram-negative ...

  7. Staining - Wikipedia

    en.wikipedia.org/wiki/Staining

    Gram Primary stain: Crystal violet applied to film then treated with iodine (mordant), alcohol (decolourizer) and counter stained with safranin Characterizes bacteria in one of two groups, Gram positive or Gram negative Gram positive appears purple in color Gram negative appears pink in color 4 Acid fast (Ziehl-Neelsen technique)

  8. Atypical bacteria - Wikipedia

    en.wikipedia.org/wiki/Atypical_bacteria

    Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet during Gram staining, resulting in a purple color. Gram-negative bacteria have a thin peptidoglycan layer which does not retain the crystal violet, so when safranin is added during the process, they stain red.

  9. Cell envelope - Wikipedia

    en.wikipedia.org/wiki/Cell_envelope

    In Gram-negative bacteria an outer membrane is also included. [1] This envelope is not present in the Mollicutes where the cell wall is absent. Bacterial cell envelopes fall into two major categories: a Gram-positive type which stains purple during Gram staining and a Gram-negative type which