Bacterial Cell Envelope

The rigid outer layer of a bacterial cell that protects it from internal pressure.

The pressure exerted by the contents of a bacterial cell against its cell wall.

A unique molecule found in bacterial cell walls that provides structural support and protects against osmotic pressure.

The formation of covalent bonds between peptidoglycan monomers to create a strong and interconnected network.

An enzyme essential for the formation of cross-links between peptidoglycan monomers, crucial for cell wall integrity.

A class of antibiotics that inhibit the activity of transpeptidase, preventing the formation of cross-links in peptidoglycan.

A type of antibiotic that prevents the release of the terminal D-alanine, inhibiting the formation of cross-bridges in peptidoglycan.

A specific type of amino acid that bacteria use in their peptidoglycan, differing from the L-amino acids found in human proteins.

The process by which bacteria synthesize and remodel their peptidoglycan cell walls as they grow and divide.

Antibiotics targeting cell walls are effective against many bacteria because bacteria constantly remodel their cell walls, leaving them vulnerable to disruption.

The envelope encloses the bacterial cytoplasm and includes the inner membrane and various external structures like peptidoglycan, outer membrane, capsule, and S-layer.

Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thinner layer.

Gram-staining is a technique used to differentiate bacteria based on the thickness of their peptidoglycan layer.

Mycobacteria have several layers of peptidoglycan, additional sugars (arabinogalactan, arabinomannan), and a waxy outer layer composed of mycolic acid.

A capsule is an outer layer primarily composed of polysaccharides that can be found in some bacteria, providing additional protection.

A complex formed by iodine and crystal violet dye, which is too large to diffuse through multiple layers of peptidoglycan found in Gram-positive bacteria, but can easily diffuse out of the thinner Gram-negative cell envelope.

Long molecules found in Gram-positive bacteria that crosslink peptidoglycan layers to each other. They can either bridge multiple layers or attach them to the cell membrane.

A functionally similar molecule to teichoic acids found in Gram-negative bacteria. This protein connects both the inner and outer membranes to the limited peptidoglycan in the periplasmic space.

A repeating protein structure composed of one or two proteins (usually glycoproteins) that forms a lattice-like layer on the surface of many bacteria. It is associated with either the peptidoglycan in Gram-positive bacteria or lipopolysaccharide (LPS) in Gram-negative bacteria.

A potent endotoxin found in the outer membrane of Gram-negative bacteria that can trigger septic shock.

Major lipids found in the outer membrane of mycobacteria, contributing to their unique properties and resistance to staining.

A waxy layer found in mycobacteria, contributing to their unique texture.

The outermost layer in some Gram-positive bacteria, including mycobacteria, providing an extra layer of protection.

A molecule with both hydrophobic and hydrophilic regions, like a double-sided coin.

A major component of the outer membrane of Gram-negative bacteria, acting as a permeability barrier.

Trimeric protein channels embedded in the cell envelope of Gram-negative bacteria and mycobacteria, allowing the passive diffusion of certain molecules.

The space between the inner and outer membranes of Gram-negative bacteria.

A surface layer found in many bacteria, including mycobacteria, providing a rigid outer layer.

The ability of molecules to move across a membrane without the need for energy.

Gram-negative bacteria have an outer membrane composed of lipopolysaccharide (LPS) that is involved in various functions including protection from host immune system, antibiotic resistance, and cell signaling.

Mycobacteria have a unique cell envelope with multiple layers, including a thick peptidoglycan layer, a layer of arabinogalactan, and an outer waxy layer of mycolic acids. This complex structure contributes to their resistance.

Porins are protein channels that allow the passage of small molecules across the outer membrane of Gram-negative bacteria, but not large antibiotics.

Efflux pumps are active transport systems that expel harmful substances from the cell, including antibiotics. Bacterial resistance can be increased by expressing higher levels of efflux pumps.

Vancomycin resistance can arise from changes in the terminal amino acids of peptidoglycan, often involving the replacement of D-alanine with D-lactate.

The cell wall of bacteria is essential for maintaining cell shape and integrity. It protects the cell from osmotic pressure and serves as a barrier to external threats.

Gram-positive bacteria have a thick layer of peptidoglycan, while Gram-negative bacteria have a thin layer. This difference affects the permeability and susceptibility to antibiotics.

The loss of certain cell wall components can affect bacterial structure and viability. For example, the loss of peptidoglycan can lead to cell lysis, while the loss of lipoproteins can weaken the outer membrane of Gram-negative bacteria.