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Gram-negative bacteria are a group of bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation, making positive identification possible. The thin peptidoglycan layer of their cell wall is sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane. After staining with crystal violet, an alcohol wash is applied which decolorizes the bacteria showing that their peptidoglycan layer is too thin to retain the stain and enabling identification. A counterstain (safranin or fuchsine) is then added which recolorizes the bacteria red or pink. Gram-positive bacteria have a thicker peptidoglycan layer in their cell wall outside the cell membrane, which retains the crystal violet stain during the alcohol wash, so long as it is timed correctly. The counter stain may also be absorbed by gram-positive bacteria but the darker crystal violet stain predominates. == Characteristics == Gram-negative bacteria display : #An inner cell membrane is present (cytoplasmic) # A thin peptidoglycan layer is present (This is much thicker in gram-positive bacteria) # Has outer membrane containing lipopolysaccharides (LPS, which consists of lipid A, core polysaccharide, and O antigen) in its outer leaflet and phospholipids in the inner leaflet # Porins exist in the outer membrane, which act like pores for particular molecules # Between the outer membrane and the cytoplasmic membrane there is a space filled with a concentrated gel-like substance called periplasm # The S-layer is directly attached to the outer membrane rather than to the peptidoglycan # If present, flagella have four supporting rings instead of two # Teichoic acids or lipoteichoic acids are absent # Lipoproteins are attached to the polysaccharide backbone # Some contain Braun's lipoprotein, which serves as a link between the outer membrane and the peptidoglycan chain by a covalent bond # Most, with very few exceptions, do not form spores 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Gram-negative bacteria」の詳細全文を読む スポンサード リンク
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