The periplasmic space in gram-negative cells is the region located between the peptidoglycan cell wall and the plasma membrane. It is occupied by a gel-like matrix, adding to the structural complexity of the gram-negative cell envelope.

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Gram-negative cells possess a cell envelope with a significantly thinner layer of peptidoglycan—no more than about $${}4$$ nm thick—compared to gram-positive cells. Their overall cell envelope structure is highly complex, featuring a periplasmic space and an outer membrane located external to the peptidoglycan layer.

Gram Negative Cell Walls

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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.

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Periplasmic Space

In gram-negative bacteria, the outer membrane is a distinct second lipid bilayer situated exterior to the thin peptidoglycan layer of the cell envelope. This membrane is firmly anchored to the underlying peptidoglycan by murein lipoprotein. A key feature of its outer leaflet is the presence of lipopolysaccharide (LPS), a complex molecule comprising an O antigen, core polysaccharide, and lipid A with attached fatty acid tails, which acts as an endotoxin during bacterial infections.

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