gram-positive

(adjective)

that is stained violet by Gram's method due to the presence of a peptidoglycan cell wall

Related Terms

Examples of gram-positive in the following topics:

  • Gram-Positive Cell Envelope

    • Gram-positive bacteria have cell envelopes made of a thick layer of peptidoglycans.
    • Gram-positive bacteria are stained dark blue or violet by Gram staining .
    • Primarily, it detects peptidoglycan, which is present in a thick layer in Gram-positive bacteria.
    • A Gram-positive results in a purple/blue color while a Gram-negative results in a pink/red color.
    • In Gram-positive bacteria, the cell wall is thick (15-80 nanometers), and consists of several layers of peptidoglycan.

  • Actinobacteria (High G + C Gram-Positive Bacteria)

    • Actinobacteria are a group of Gram-positive bacteria with high guanine and cytosine content in their DNA.
    • Actinobacteria are a group of Gram-positive bacteria with high guanine and cytosine content in their DNA.
    • Unlike the Firmicutes, the other main group of Gram-positive bacteria, they have DNA with a high GC-content, and some Actinomycetes species produce external spores.
    • Classification of Gardnerella is controversial, and MeSH catalogues it as both a gram-positive and gram-negative organism.

  • Shared Features of Bacteria and Archaea

    • Within prokaryotes, archaeal cell structure is most similar to that of Gram-positive bacteria, largely because both have a single lipid bilayer and usually contain a thick sacculus of varying chemical composition.
    • In phylogenetic trees based upon different gene/protein sequences of prokaryotic homologs, the archaeal homologs are more closely related to those of Gram-positive bacteria.
    • Archaea and Gram-positive bacteria also share conserved indels in a number of important proteins, such as Hsp70 and glutamine synthetase I.
    • Gupta has proposed that the Archaea evolved from Gram-positive bacteria in response to antibiotic selection pressure.
    • Gupta's proposal is also supported by other work investigating protein structural relationships and studies that suggest that Gram-positive bacteria may constitute the earliest branching lineages within the prokaryotes.

  • Spectrum of Antimicrobial Activity

    • Broad spectrum—antibiotics act against gram positive and gram negative bacteria, for example amoxicillin.
    • Gram staining (or Gram's method; is a method of differentiating bacterial species into two large groups (Gram-positive and Gram-negative).
    • Primarily, it detects peptidoglycan, which is present in a thick layer in Gram positive bacteria.
    • A Gram positive results in a purple/blue color while a Gram negative results in a pink/red color.
    • This is a microscopic image of a Gram stain of mixed Gram-positive cocci (Staphylococcus aureus, purple) and Gram-negative bacilli (Escherichia coli, red).

  • Overview of Gram-Positive Bacteria and Actinobacteria

    • Actinobacteria are Gram-positive bacteria with high guanine and cytosine content in their DNA and can be terrestrial or aquatic.
    • They are Gram-positive bacteria with high guanine and cytosine content in their DNA and can be terrestrial or aquatic.
    • Unlike the Firmicutes, the other main group of Gram-positive bacteria, they have DNA with a high GC-content, and some Actinomycetes species produce external spores.

  • Peptidoglycan Synthesis and Cell Division

    • Peptidoglycan forms around 90% of the dry weight of Gram-positive bacteria but only 10% of Gram-negative strains.
    • In Gram-positive strains, it is important in attachment roles and stereotyping purposes.
    • For both Gram-positive and Gram-negative bacteria, particles of approximately 2 nm can pass through the peptidoglycan.
    • Gram-positive and Gram-negative bacteria are sensitive to different types of antiobiotics.
    • Simplified sc hematic of a cell wall in a Gram-positive bacteria

  • Basic Structures of Prokaryotic Cells

    • Bacteria are divided into two major groups: gram-positive and gram-negative, based on their reaction to gram staining.
    • Gram-positive organisms typically lack the outer membrane found in gram-negative organisms .
    • Bacteria are divided into two major groups: gram-positive and gram-negative.
    • Both groups have a cell wall composed of peptidoglycan: in gram-positive bacteria, the wall is thick, whereas in gram-negative bacteria, the wall is thin.
    • In gram-positive bacteria, lipoteichoic acid anchors the cell wall to the cell membrane.

  • Bacterial Pneumonias

    • Gram Positive.
    • Streptococcus pneumoniae is a Gram-positive bacterium that often lives in the throat of people who do not have pneumonia.
    • Other important Gram-positive causes of pneumonia are Staphylococcus aureus and Bacillus anthracis.
    • Gram Negative.
    • In reality, they are "atypical" because they do not gram stain as well as gram-negative and gram-positive organisms.

  • Phenotypic Analysis

    • Within prokaryotes, archaeal cell structure is most similar to that of Gram-positive bacteria.
    • The Gram stain, developed in 1884 by Hans Christian Gram, characterizes bacteria based on the structural characteristics of their cell walls.
    • The thick layers of peptidoglycan in the "Gram-positive" cell wall stain purple , while the thin "Gram-negative" cell wall appears pink.
    • By combining morphology and Gram-staining, most bacteria can be classified as belonging to one of four groups (Gram-positive cocci, Gram-positive bacilli, Gram-negative cocci, and Gram-negative bacilli).
    • Some organisms are best identified by stains other than the Gram stain, particularly mycobacteria or Nocardia, which show acid-fastness on Ziehl–Neelsen or similar stains.

  • Gram-Negative Outer Membrane

    • The Gram-negative cell wall is composed of an outer membrane, a peptidoglygan layer, and a periplasm.
    • In the Gram-negative Bacteria the cell wall is composed of a single layer of peptidoglycan surrounded by a membranous structure called the outer membrane.
    • The safranin is responsible for the red or pink color seen with a gram-negative bacteria.
    • The Gram-negative's cell wall is thinner (10 nanometers thick) and less compact than that of Gram-positive bacteria, but remains strong, tough, and elastic to give them shape and protect them against extreme environmental conditions .
    • Together, the plasma membrane and the cell wall (outer membrane, peptidoglycan layer, and periplasm) constitute the gram-negative envelope.