680 likes | 1.46k Views
Bacterial Morphology Arrangement. 1. Bacilli a.Streptobacilli b. Bacilli 2. Cocci a. Cocci b. Doplococci c. Streptococci d. Staphylococci e. Sarcina ( 3D ) f. Gaffkya ( 2D ) . Common Shapes & Arrangement. Bacterial morphologies (1). Bacterial morphologies (2).
E N D
Bacterial Morphology Arrangement 1. Bacilli a.Streptobacilli b. Bacilli 2. Cocci a. Cocci b. Doplococci c. Streptococci d. Staphylococci e. Sarcina ( 3D ) f. Gaffkya ( 2D )
Bacterial Morphology Arrangement 3 Spirl a. Vibrio b. Spirillum c. Spirochete
Bacterial Cell Structure • Appendages - fdlagella, pili or fimbriae • Surface layers - capsule, cell wall, cell membrane • Cytoplasm - nuclear material, ribosome, mesosome, inclusions etc. • Special structure - endospore
Appendages 1. flagella Some rods and spiral form have this. a). function: motility b). origin : cell membrane flagella attach to the cell by hook and basal body which consists of set(s) of rings and rods Gram - : 2 sets of ring and rods, L, P, S, M rings and rods e.g. E. coli Gram + : S, M rings and rods e.g. B. megaterium
b).Origin (continued) • The structure of the bacterial flagella allows it to spin like a propeller and thereby propel the bacterial cell; clockwise or counter clockwise ( Eucaryotic , wave like motion. • Bacterial flagella provides the bacterium with mechanism for swimming toward or away from chemical stimuli, a behavior is knows as CHEMOTAXIX, chemosenors in the cell envelope can detect certain chemicals and signal the flagella to respond.
c). position monotrichous lophotrichous peritrichous d). structure protein in nature: subunit flagellin
2. Pili or Fimbriae Shorter than flagella and straighter , smaller. Only on some gram- bacteria. a). function: adhere. One of the invasive mechanism on bacteria. Some pathogens cause diseases due to this. If mutant (fimbriae) not virulent. Prevent phagocytosis.
pili - sex factor. If they make pili, they are + or donors of F factor. It is necessary for bacterial conjugation resulting in the transfer of DNA from one cell to another. It have been implicated in the ability of bacteria to recognize specific receptor sites on the host cell membrane. In addition, number of bacteria virus infect only those bacteria have F pilus.
b). Origin: Cell membrane c). Position: common pili , numerous over the cell, usually called fimbriae sex pile, 1-4/cell d). Structure: composed of proteins which can be dissociated into smaller unit Pilin . It belongs to a class of protein Lectin which bond to cell surface polysaccharide.
II. CELL SURFACE LAYER 1. Capsule or slime layer Many bacteria are able to secrete material that adheres to the bacterial cell but is actually external to the cell. It consists of polypeptide and polysaccharide on bacilli. Most of them have only polysaccharide. It is a protective layer that resists host phagocytosis. Medically important.
2. Bacterial Cell Wall General structure: mucopolysaccharide i.e. peptidoglycan. It is made by N-acetylglucosamine and N-acetylmuramic acid. tetrapeptide ( L-alanine- isoglutamine-lysine-alanine) is attached. The entire cell wall structure is cross linked by covalent bonds. This provide the rigidity necessary to maintain the integrity of the cell. N-acetylmuramic acid is unique to prokaryotic cell.
(a). Gram positive bacterial cell wall Thick peptidoglycan layer pentaglycin cross linkage. Teichoic acid: ribitol TA & glycerol TA Some have peptioglycan teichoic acid. All have lipoteichoic acid.
Function of TA: * Antigenic determinant * Participate in the supply of Mg to the cell by binding Mg++ * regulate normal cell division. For most part, protein is not found as a constituent of the G+ cell wall except M protein on group streptococci
(b) Gram - Thin peptidoglycan Tetrapeptide cross linkage A second membrane structure: protein and lipopolysaccharide. Toxicity : endotoxin on lipid A of lipopolysaccharide. glucosamine- glucosamine-long polysaccharide- repeated sequences of a few sugars (e.g. gal- mann-rham) n=10-20 O antigen
Toxicity : endotoxin on lipid A of lipopolysaccharide. glucosamine- glucosamine-long FA FAFA FA polysaccharide- repeated sequences of a few sugars (e.g. gal- mann-rham) n=10-20 O antigen
2. Cell Membrane Function: a. control permeability b. transport e’s and protons for cellular metabolism c. contain enzymes to synthesis and transport cell wall substance and for metabolism d. secret hydrolytic enzymes e. regulate cell division. • Fluid mosaic model. phospholipid bilayer and protein (structure and enzymatic function). Similar to eukaryotic cell membrane but some differs. e.g. sterols such as cholesterol in Euk not in Prok.
III. Cytoplasm 80% water, nucleic acids, proteins, carbohydrates, lipid and inorganic ions etc. 1. Bacterial chromosomes a single large circular double stranded DNA no histone proteins. The only proteins associated with the bacterial chromosomes are the ones for DNA replication, transcription etc. 2. Ribosome protein synthesis
3. Mesosomes A large invaginations of the plasma membrane, irregular in shape. a. increase in membrane surface, which may be useful as a site for enzyme activity in respiration and transport. b. may participate in cell replication by serving as a place of attachment for the bacterial chromosome.