Bacterial morphology

Structure of the bacterial cell I- Bacterial cell wall 1) definition 2) function 3) chemical composition 4) Difference between G +ve & G -ve 5) Mycoplama 6) L form

Structure of the bacterial cell I- Bacterial cell wall 1) definition -It's the outermost basic component of all bacteria - It's multilayered structure located external to cytoplasmic membrane

Structure of the bacterial cell I- Bacterial cell wall 2) function - Maintain the shape: rigid structure - Protect and support C M: Osmotically insensitive - Has role in replication: transverse septum -Responsible stain affinity: G +ve or G –ve

I- Bacterial cell wall 3) chemical composition A- In gram +ve bacteria: Thick but simple 1 – Peptidoglycan (P. G): - This is the basic structure of cell wall - Composed of about 40 sheet or 50% of cell wall content - Formed of repeating unit of N acetyl-D- glucosamin and N acetyl muramic acid. That form sheet surrounding CM 2 - Techoic acid: - Formed of polymer of ribitol and glycerol, mixed on both sides of P.G - it mediate adherence of bacteria to mucosal surface both P.G and Techoic acid are the major surface antigen in gram +ve bacteria NAG NAG NAM NAM

I- Bacterial cell wall 2) chemical composition A- In gram +ve bacteria: Thick but simple

I- Bacterial cell wall 2) chemical composition B- In gram -ve bacteria: thin but complex 1 – Peptidoglycan (P. G): (mention its structure) - It form thin layer formed of 1or 2 sheets and constitute about 5-10 % of cell wall of G-ve cell wall 2- Outer membrane: - formed of phospholipids bilayer and proteins (similar to Cytoplasmic membrane) 3- Lipoprotein: cross link P G and outer membrane

I- Bacterial cell wall 4- Lipopolysacchrides (LPS): 2) chemical composition 4- Lipopolysacchrides (LPS): - attached to outer membrane - formed of inner part called lipid A and the polysaccharide core then - polysaccharide side chain that called somatic (O) antigen. - LPS is called endotoxin as when it is released after bacterial lysis - it induce toxic manifestation called endotoxic shock syndrome 5- Periplasmic space: - The space between cytoplasmic membrane and outer membrane - It contain PG, lipoprotein, and gel like structure contain many enzymes as beta Lactamase enzyme core Lipid A Outer M

Structure of the bacterial cell

Diference in Structure

Bacteria deficient in cell wall * Definition: they are bacteria that don’t have cell wall *Types: cell wall deficient bacterial may be natural as mycoplasma or induced as L-form that are formed in presence of cell wall inhibitor as lysozyme or drug as penicillin that interfere with P G * L form may be of two types 1- Spheroplast: formed from G -ve bacteria and sill contain outer membrane 2- protoplast: formed from G +ve bacteria and don’t contain outer m. * Importance of L form: It may be formed during antibiotic treatment so it become resistant to its action then their reversion to the walled stat leads to relapse and chronicity of infection

Bacteria deficint in cell wall Comparison: Mycoplasma L- form Table 2 It’s bacteria that naturally devoid of cell wall. It’s bacteria é removed or damaged cell wall. Definition No external influence. Due to inhibitor in the media as penicillin or lysozyme Cause Can’t Can revert it the inhibitor removed Reverting to walled state Solid or fluid é cholesterol Grow only on solid media Media Less More fragile Fragility Some species may cause respiratory or genital diseases. Responsible for chronicity of infection and drug resistance Importance

Structure of the bacterial cell II- Bacterial cytoplasmic M 1) composition 2) functions 3) Mesosomes 4) intracytoplasmic structures

II- Bacterial cytoplasmic M 1) composition Composition: phospholipids bilayer and proteins but unlike eukaryotes doesn’t contain sterols except in Mycoplasma Mesosomes: they are invaginations of the cytoplasmic membrane into the cytoplasm the are involved in many function as respiration, cell division and spore formation.

II- Bacterial cytoplasmic M 2) Functions 1- Selective permeability: for nutrients through - Simple diffusions: down to concentration gradient, no energy - Facilitated diffusion: for large molecules also no energy. - Active transport: against concentration gradient so energy is needed. 2- Respiration: by oxidative phosphorylation and electron transport, instead of Mitochondria in eukaryotes. 3- Excretion of extracelluar enzymes and toxins

II- Bacterial cytoplasmic M 2) Functions 4- Role in cell division as it provide - Site of attachment of chromosome before duplication - Synthesis of cell wall septum for separation of the two cells 5- Provide enzymes and lipid carrier for cell wall synthesis 6- Chemotactic for bacterial response to man attractant or repellant through its receptors e.g. attraction of motile bacteria toward glucose

II- Bacterial cytoplasmic M 4)intracytoplasmic structures 1- Nucleoid body : formed of single circular, chromosomecoiled on itself without nuclear membrane. 2- Plasmid: it is extra-chromosomal double stranded circular DNA smaller than chromosome and carries genes not essential for life. 3- Ribosome: it is of 70s type formed of 2 subunits 50s and 30s It is the site of protein synthesis. 4- Inclusion: many types of inclusion may present as volutin granules which are food reserve for ATP production.

Structure of the bacterial cell III- Bacterial Capsule 1) Definition 2) composition 3) Importance 4) Glycocalyx

Bacterial Capsule 1) Definition: it is the outermost well defined layer in capsulated organism while if ill defined it is called glycocalyx 2) Composition: it is in vivo structure mostly formed of polysaccharides except in B. antracis formed of polypeptides

Bacterial Capsule 3) Importance (functions) 1- Virulence factor: antiphagocytic factor 2-Protection of call wall from antibacterial agent as lysozyme and bacteriophage 3 - Help bacterial attachment and biofilm formation (glycocalyx) 5 - Reservoir for certain nutrient 6 - used in diagnosis 7 - used in formation of vaccines. 8 - used in serotyping

Structure of the bacterial cell IV- Bacterial Flagella 1 - structure 2 - importance 3 - types

Bacterial Flagella Structure - these are long thin filamentous appendages that are attached to the cell wall and C.M by basal body. - consist of protein called flagilin which is antigenic and called (H) antigen. function : these are organ of motility in motile bacteria that move toward nutrient and attractant (chemotaxis).

Bacterial Flagella - Types According to distribution: many distribution form present but it is constant in the same species, it may be A - monotrichous, B - lophotrichous C - amphotrichous, D - peritrichous

Bacterial Flagella 1) structure - importance - types

Structure of the bacterial cell V- Bacterial pili Definition: these are hair like projections of cell similar to flagella but smaller * Composition: formed of protein called pilin *Types and Function: 2 types of 2 different functions 1- Ordinary pili: mediate adherence of the organism to the epithelial surface e.g. N. gonorrhea adhere pili to mucosa of urethra 2- Sex pili: responsible of conjugation (see Genetic).