These are the polymers of glycerol and ribitol linked by phosphate moiety. The cell wall of gram-positive bacteria contains acidic negatively charged substances called teichoic acid. This peptide cross-link reaction is called transpeptidation. The peptide interbridge if present connects tetrapeptide chains. A carboxyl group of NAM tetrapeptide chains made of alternate D and L amino acids is linked. These derivatives are linked together by β-1,4 glycosidic bonds. Peptidoglycan is a polymer having two sugar derivatives. The cell wall of gram-positive and negative bacteria is made of peptidoglycan, also called murein. Reproduction is either by binary fission or budding.Ĭell Wall Structure of Gram-Positive and Gram-Negative Bacteria They are round, rod or spherical in shape. They bear appendages like pili and fimbriae for motility. This group is composed of a 2 to 7 nm thick peptidoglycan layer surrounded by an outer membrane. In gram staining, they appear red or pink as they do not retain the colour of crystal violet dye. The two major groups are Enterobacteriaceae and the non-fermenters. The gram-negative bacteria belong to the phylum Pseudomonadota. In gram staining procedures, they appear purple yielding positive results.Ĭell Wall Structure of Gram-Positive Bacteria and Gram-Negative Bacteria Phylum Actinobacteria - Have high GC content. The two major divisions of gram-positive bacteria are: Gram-positive and gram-negative bacteria difference pdf can be downloaded for more information. This difference lies in morphological variation seen in the cell wall structure of both gram-positive and gram-negative bacteria. The bacteria that retain the Gram stain are gram-positive while which does not retain the gram stain are gram-negative bacteria. In 1884, Christian Gram invented the staining procedure to classify bacteria. These groups of bacteria are a serious threat as they cause major diseases in humans.Īll prokaryotic cells are surrounded by a complex cell made of peptidoglycan, also known as murein. Examples of gram-positive bacteria are Methicillin-resistant Staphylococcus aureus (MRSA), and examples of gram-negative bacteria are Salmonella, Pneumonia and Gonorrhea. The size varies from 0.2 µm to 50 µm having varied morphology in their appearance. Bacteria are unicellular prokaryotic organisms devoid of nuclei.
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