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Gram-positive bacteria
- Appear blue after Gram staining
- Have a thick cell wall with multilayered murein
- Possess pondonic acids anchored in the cell wall
- Have only one membrane (cytoplasmic membrane), into which lipoteichoic acids are anchored.
- Due to the lack of an outer membrane, gram-positive bacteria are well permeable to exogenous substances
- Gram-positive bacteria are mainly cocci
Examples of gram-positive bacteria:
- Staphylococci, e.g. S. aureus.
- Streptococci, e.g., S. pyogenes
- Listeria
- Clostridia
- Mycobacteria
- Nocardia
Gram-negative bacteria
- Appear red after Gram staining
- Have a thin cell wall with single-layered murein
- Contain two membranes (outer membrane and cytoplasmic membrane).
- Possess lipopolysaccharides anchored in the outer cell membrane, which act as endotoxins when the bacteria decay.
- The outer membrane has low permeability, but contains pores through which the influx is regulated
- Gram-negative bacteria are mainly rods
Examples of gram-negative bacteria:
- Pseudomonads
- Legionella
- Bordetella, e.g. Bordetella pertussis
- Campylobacter
- Helicobacter pylori
- Enterobacteriaceae, e.g. E. coli, salmonellae
- Borrelia
- Chlamydia (intracellular)
- Nisseria
Literature
- Gross U. Kurzlehrbuch medizinische Mikrobiologie und Infektiologie, Georg Thieme Verlag, 2006.
- Pagès J.M. et al. The porin and the permeating antibiotic: a selective diffusion barrier in gram-negative bacteria. Nature Reviews Microbiology, 2008, 6(12), 893-903 Pubmed.
- Weidenmaier C., Peschel A. Teichoic acids and related cell-wall glycopolymers in gram-positive physiology and host interactions. Nature Reviews Microbiology, 2008, 6(4), 276-87 Pubmed.
