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...

    Gene Regulation in Eukaryotes
    Gene Regulation in Eukaryotes

    Learn about the general structure of a eukaryotic gene, the transcription factors, and post-transcriptional regulation....

    DNA molecule
    Genetic Control – On and Off Genes

    Genes are the blueprint of our bodies, a blueprint that creates a variety of proteins essential to any organism's surviv..

    Kidneys
    Kidneys and Regulation of Water and Inorganic Ions

    The kidneys are responsible for the regulation of water and inorganic ions. Read this tutorial to learn about the differ..

    Chromosome Mutations
    Chromosome Mutations

    Mutations can also influence the phenotype of an organism. This tutorial looks at the effects of chromosomal mutations, ..

    vitamins
    A Balanced Vitamin Diet – Vitamins A – K

    A balanced diet is essential to a healthy organism. Insufficiency or too much of a particular element or compound, such ..

    A sperm cell fertilizing an ovum
    Human Reproduction and Fertilization

    For human species to obviate extinction, reproductive mature adults should be producing viable offspring in order to con..

    Related Articles...

    No related articles found

    See all Related Topics