12 Appendages 1. flagella e.g. B. megaterium Some rods and spiral form have this.a). function: motilityb). origin : cell membrane flagella attach to the cell by hook and basal body which consists of set(s) of rings and rodsGram - : 2 sets of ring and rods, L, P, S, M rings and rodse.g. E. coliGram + : S, M rings and rodse.g. B. megaterium
18 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.
19 c). positionmonotrichouslophotrichousperitrichousd). structureprotein in nature: subunit flagellin
20 2. Pili or FimbriaeShorter 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.
21 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.
22 b). Origin: Cell membrane c). Position: common pili , numerous over the cell, usually called fimbriae sex pile, 1-4/celld). Structure: composed of proteins which can be dissociated into smaller unitPilin . It belongs to a class of protein Lectin which bond to cell surface polysaccharide.
23 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.
24 2. Bacterial Cell WallGeneral 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.
31 (a). Gram positive bacterial cell wall Thick peptidoglycan layerpentaglycin cross linkage.Teichoic acid: ribitol TA & glycerol TASome have peptioglycan teichoic acid.All have lipoteichoic acid.
32 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
34 (b) Gram -Thin peptidoglycanTetrapeptide cross linkageA second membrane structure: protein and lipopolysaccharide.Toxicity : endotoxin on lipid A of lipopolysaccharide. glucosamine- glucosamine-longpolysaccharide- repeated sequences of a few sugars (e.g. gal- mann-rham) n= O antigen
40 2. Cell MembraneFunction:a. control permeabilityb. transport e’s and protons for cellular metabolismc. contain enzymes to synthesis and transportcell wall substance and for metabolismd. secret hydrolytic enzymese. 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.
48 III. Cytoplasm80% water, nucleic acids, proteins, carbohydrates, lipid and inorganic ions etc.1. Bacterial chromosomesa 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. Ribosomeprotein synthesis
50 3. MesosomesA 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.
51 4. Inclusions Not separate by a membrane but distinct. Granules of various kinds:* glycogen,*polyhydroxybutyric acid droplets (PHB)i.e. fat droplets* inorganic metaphosphate (metachromatic granules) - in general, starvation of cell for almost any nutrients leads to the formation of this to serve as an intracellular phosphate reservoir.
53 5. ChromatophoresOnly in photosynthetic bacteria and blue green algae. Prok. no chloroplast, pigment found in lamellae located beneath the cell membrane.
54 IV. Special Structure* EndosporesSpore former: sporobactobacilli and sporosarcinae - no medical importance. bacillus and clostridium have medical importance.* Position: median, sub-terminal and terminal have small water, high calcium content and dipicolinic acid (calcium dipicolinate)extremely resistant to heat, UV, chemicals etc. may be due to many S containing A.A for disulfide groups.
55 The process of endospore formation After the active growth period approaching the stationary growth phase, a structure called forespore develops within the cells.It consists of coat, cortex and nuclear structure.