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...

    running freshwater community
    Running Water Freshwater Community Factors

    This tutorial noted some of the physical and chemical factors that provide the framework of a running water community in..

    primitive arthropods
    Arthropods

    The arthropods were assumed to be the first taxon of species to possess jointed limbs and exoskeleton, exhibit more adva..

    Hominid
    The Hominids

    The hominid family diversified from the apes around 6 to 8 million years ago. Since then, the evolutionary path has prov..

    Sigmund Freud and Carl Gustav Jung
    Sigmund Freud and Carl Gustav Jung

    In this tutorial, the works of Carl Gustav Jung and Sigmund Freud are described. Both of them actively pursued the way h..

    Population Growth and Survivorship
    Population Growth and Survivorship

    This lesson looks at population attributes, regulation, and growth. It also covers population genetics, particularly gen..

    Adaptation Tutorial
    Adaptation Tutorial

    Adaptation, in biology and ecology, refers to the process or trait through which organisms or the populations in a habit..

    Related Articles...

    No related articles found

    See all Related Topics