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...

    Ploidy
    Polyploidy

    Humans are diploid creatures. This means that for every chromosome in the body, there is another one to match it. Howeve..

    The process of photosynthesis
    Photosynthesis – Photolysis and Carbon Fixation

    Photosynthesis is the process that plants undertake to create organic materials from carbon dioxide and water, with the ..

    New Zealand Fauna
    New Zealand’s Unique Fauna

    Meet some of New Zealand's unique fauna, including endemic insects, frogs, reptiles, birds, and mammals, and investigate..

    sponge
    Primitive Animals

    Life, as we know it today, is presumed to have started in the sea and many of them were likely eukaryotic animal-like or..

    Human gastrointestinal tract
    Human Biology – Food and Digestion

    This tutorial recognizes the importance of food as a source of energy that will fuel many biological processes. A good d..

    Ecosystem Succession
    Ecosystem Succession

    If the balance of nature is left untouched, landscapes can change dramatically over time. A previous ecosystem is supers..

    Related Articles...

    No related articles found

    See all Related Topics