> See also: > - [[Microbiology]] > - [[Bacteria]] # Bacteria Cell Envelope The cell wall functions - Shape - Protection (Preventing implosion in hypotonic environments) - Pathogenicity (virulence factors) ## Cell Wall > [!summary] **Peptidoglycan Structure** > - B(1-4) glycosidic bonds connect horizontally between *N-acetylglucosamine (NAG)* and *N-acetylmuramic acid (NAM)* sugars while they are connected vertically through **peptide bonds** > ![[Pasted image 20231003142011.png|300]] ^peptidoglycan-structure Natural amino acids are normally L- configured, however many within the peptidoglycan structure are instead D- configured, allowing them to evade a lot of enzymatic activity Mycoplasma are one of the few bacteria that completely lack a cell wall, contributing to their pleomorphic (varied/random) morphology Extracellular Vesicles are small membrane-bound particles that form when a portion of a cell envelope buds out and pinches off ### Cell Wall Growth UDP derivatives of NAM & NAG are the starting point Bactroprenol assists in transportation of this starting material from the cytoplasm across the plasma membrane ### Cell Wall Modifications Penicillin inhibits the cell while but does not lyse it. A lysozyme is capable of breaking the B(1-4) bonds found within peptidoglycans If a bacteria’s cell wall was removed: - *Gram negatives* become **spheroplasts** - *Gram positives* would become **protoplasts** L-form bacteria are capable of turning their cell wall on or off depending on if they are in a [[Diffusion and Osmosis|hypotonic]] environment. ### Gram Negative vs Gram Positive > See also > - [[Gram Staining]] > [!important] > Both gram negative and gram positive bacteria have an overall negative charge on their cell wall. > However, because gram negative bacteria have a signif Teichoic Acids (Gives negative charge) can be embedded in the ticker cell wall of gram-positive bacteria Exoenzymes Gram Negative - LPS (Lipopolysaccharide) - can be considered the gram negative version of teichoic acids as both are long polymeric chain molecules - No teichoic acids - embedded in outer membrane and protrude from cell ![[Bacteria Cell Envelope.png|222]] Lipoteichoic acid (LTA) is bound to the cellular membrane while normal teichoic acids (TA) are only embedded in the peptidoglycan cell wall. > [!note] LipoPolySaccharides (LPS) > Contents > ![[Bacterial Cell Wall.png]] > Can release endotoxins (lipid A) when lysed > B(1→4) Glycosidic Bonds ## Layers Outside the Cell Wall > See also > - [[Cell Motility]] ![[Pasted image 20230913171034.png]] ### S-Layers S(Surface)-Layers are self assembling unlike peptidoglycan - Potential use in nanotechnology - Organized protein layer These often have a regular geometric pattern (organized structure) similar to floor types ### Capsules **Capsules** (or *capsid*) are well-organized layers often composed of [[Carbohydrates|polysaccharides]]. In *gram negative* bacteria the capsule is capable of covalently bonding to the outer membrane lipids, making it difficult to wash away - Typically composed of sugars - Capsules provide protein from - Protect against dessication (drying out) as they contain a lot of water ### Slime Layers Slime Layer - Disorganized Sugar Layer Slime layers are often very disorganized ### Cell Envelope > See also: > - [[Cytoskeletons]] FtsZ - Tubulin Homologue - Center of cell MreB - Actin Homologue - Converts to rod shape CreS - Intermediate Filament Homologue - Maintains curve shape ![[Pasted image 20231204093558.png|400]]