Gram-Positive Bacteria – Disease, Health and Probiotics

In microbiology, the visualization of bacteria at the microscopic level is facilitated by the use of stains, which react with components present in some cells but not others. This technique is used to classify bacteria as either Gram-positive or Gram-negative depending on their colour following a specific staining procedure originally developed by Hans Christian Gram. Gram-positive bacteria appear dark blue or violet due to the crystal violet stain following the Gram stain procedure; Gram-negative bacteria, which cannot retain the crystal violet stain, appear red or pink due to the counterstain. Gram-positive bacteria retain the crystal violet due to the amount of peptidoglycan in the cell wall.

Gram-positive bacteria are divided into two main groups: the Actinobacteria and the Firmicutes. The Actinobacteria have a high G+C ratio and include common soil bacteria and some pathogens, such as Mycobacterium and Corynebacterium. Strains of Mycobacterium can cause tuberculosis and   leprosy . Strains of Corynebacterium can cause diphtheria, granulomatous lymphadenitis, pneumonitis, pharyngitis, skin infections, and endocarditis. The Firmicutes have a low G+C content in contrast to the Actinobacteria. Firmicutes can be cocci or rod-shaped forms. Many produce endospores. They are found in various environments and some are important pathogens, for example Bacillus, Listeria, Staphylococcus, and Streptococcus.

In contrast, strains of Lactobacillus are important for health and live Lactobacillus bacteria are constituents of many probiotics. Lactic acid bacteria (LAB) such as Lactobacillus and Bifidobacterium are probiotics that have numerous potential therapeutic properties including anti-inflammatory and anti-cancer activities. Lactococcus is an important organism in the food industry and is used to produce cheese and yoghurts and other fermented foods. Strains of Clostridium are being considered as a means of selectively targeting and destroying cancer cells especially for the treatment of solid tumors.

  • Actinobacteria
    • Actinomyces
    • Arthrobacter
    • Corynebacterium
    • Frankia
    • Micrococcus
    • Micromonospora
    • Mycobacterium
    • Nocardia
    • Propionibacterium
    • Streptomyces
  • Firmicutes
    • Acetobacterium
    • Bacillus
    • Clostridium
    • Enterococcus
    • Erysipelothrix
    • Eubacterium
    • Heliobacterium
    • Heliospirillum
    • Lactobacillus
    • Lactococcus
    • Leuconostoc
    • Listeria
    • Pectinatus
    • Pediococcus
    • Selenomonas
    • Spiroplasma
    • Sporomusa
    • Staphylococcus
    • Streptococcus
    • Megasphaera
    • Mycoplasma
    • Ureaplasma
    • Zymophilus