In gram positive bacteria, the NAM molecules of peptidoglycan are linked with tetrapaptide links. These tetrapeptide molecules are not present in gram negative bacteria. In gram positive bacteria, the peptidoglycan later is much larger compared to gram negative bacteria. They also have a layer of teichoic acid on the external side of the plasma membrane which makes the wall more rigid.

Gram Positive Cell Walls

Gram negative bacteria have a thin layer of peptidoglycan. They also have an inner and outer membrane. The outer membrane contains the lipopolysaccharides which are important in gram negative bacteria being infectious. 

Gram Negative Cell Walls

University of Wisconsin - Madison

Peptidoglycan makes up the cell walls of bacteria. It is composed of alterating long chain molecules called N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). NAM and NAG are connected to each other with peptide bridges. Peptidoglycan is only in bacteria which makes it a key target for antibiotics.

Peptidoglycan

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Types of Bacterial Cell Walls

Archaeal walls are different from bacteria because they do not contain peptidoglycan. Some contain pseudopeptidoglycan or have a cell wall made of glycoproteins or sugars. Some lack a cell wall entirely. 

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