Dictionary > Gram-positive bacteria

Gram-positive bacteria

Definition
noun, singular: gram-positive bacterium
A group of bacterial cells that retains the violet colour following Gram’s method
Supplement
Gram staining is a method used to classify a bacterial species into gram-positive or gram-negative. Gram-positive bacteria tend to retain the primary stain and are no longer stained by the counterstain. That is because they have thick cell walls. The thick cell wall in this group of bacteria is due to the presence of high peptidoglycan that crosslink forming the cell wall. They also have lower lipid content compared to those of the gram-negative bacteria. Their thick cell walls resist decolorization when the smear is washed and flooded with the solvent (a mix of alcohol and acetone) after the initial staining. The solvent dehydrates their cell walls thereby preventing the primary dye (complexed with iodine) from being washed. 1 Thus, they appear violet or blue-black under the microscope. Nevertheless, prolonged exposure to the solvent will eventually remove the primary stain in gram-positive bacteria. Thus, timing is important in performing gram staining to prevent wrong interpretation of the result.
Examples of bacterial species that are gram-positive are Staphylococcus sp. and Streptococcus sp..
Compare:

  • gram-negative bacteria

See also:

  • gram staining
  • Related term(s):

    Reference(s):

    1G. Xu. 1997. Gram stain. ://www.uphs.upenn.edu/bugdrug/antibiotic-manual/Gram1.htm Link


    You will also like...

    Selective Breeding
    Selective Breeding

    Gregor Mendel's studies into Monohybrid and Dihybrid crossing and Charles Darwin's study of evolution and natural select..

    Freshwater Ecology
    Freshwater Ecology

    Freshwater ecology focuses on the relations of aquatic organisms to their freshwater habitats. There are two forms of co..

    Neurology of Illusions
    Neurology of Illusions

    Illusions are the perceptions and sensory data obtained from situations in which human error prevents us from seeing the..

    squirrel
    Animal Water Regulation

    Animals adapt to their environment in aspects of anatomy, physiology, and behavior. This tutorial will help you understa..

    Lentic community
    Freshwater Communities & Lentic Waters

    Lentic or still water communities can vary greatly in appearance -- from a small temporary puddle to a large lake. The s..

    Genetics – Lesson Outline & Worksheets
    Genetics – Lesson Outline & Worksheets

      Topics Modules Quizzes/Worksheets Description Introduction to Genetics Genetics – Definition: Heredity and ..

    Related Articles...

    No related articles found

    See all Related Topics