A bacterium with an absent cell wall is referred to as a protoplast. Cell walls may be destroyed due to lysosomal enzymes that break down foreign pathogens through the destruction of peptidoglycan.  Although the cell is metabolically active, it is unable to reproduce. Antibiotics degrade bacteria to produce protoplasts which cannot replicate, thus treating the bacterial infection. 

Protoplast

A bacterium with a damaged cell wall is classified as a spheroplast. It may be caused by toxic chemicals or antibiotics; however, bacterial colonies can grow when the toxic agent is removed from the environment. 

Spheroplasts

Lipid A is one of the three core structural components of a lipopolysaccharide (LPS) molecule, forming part of the structure located in the outer membrane of gram-negative bacteria.

Lipid A

The core polysaccharide is a specific structural component of the lipopolysaccharide (LPS) molecule, serving to connect the Lipid A region to the O side chain in the outer membrane of gram-negative bacteria.

Core Polysaccharide

The O side chain is a component of the lipopolysaccharide (LPS) molecule in gram-negative bacteria. It is composed of sugar-like molecules and forms the external face of the LPS. The composition of the O side chain varies significantly between different bacterial species and strains.

O Side Chain

Antigens are specific parts of the O side chain on lipopolysaccharide (LPS) molecules. These antigens can be targeted and detected using serological or immunological tests, which helps to identify specific pathogenic bacterial strains, such as the deadly Escherichia coli O157:H7.

O Side Chain Antigens

Lipopolysaccharide (LPS) is a molecule located in the outer leaflet of the outer membrane of gram-negative bacteria. During infections involving these bacteria, LPS functions as an endotoxin, contributing to severe symptoms such as fever, hemorrhaging, and septic shock. Structurally, each LPS molecule is composed of Lipid A, a core polysaccharide, and an O side chain.

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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.

Outer Membrane

An endotoxin is a type of toxin that is found within the outer membrane of certain Gram-negative bacteria. Endotoxins are made within the cell remain associated with the cell until released when the cells die and disintegrate.

Endotoxins

Al-mohanna, Moshtaq & H., quine. (2016). MORPHOLOGY AND CLASSIFICATION OF BACTERIA. 

Morphology and Classification of Bacteria

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

Lipopolysaccharide (LPS)

Murein lipoprotein is a structural molecule that attaches the outer membrane to the peptidoglycan layer within the complex cell envelope of gram-negative bacteria.

Murein Lipoprotein

Exotoxins differ from endotoxin in several key characteristics. In contrast to endotoxin, which stimulates a general systemic inflammatory response when released, exotoxins are much more specific in their action and the cell components that they target.

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