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Bacterial morphology

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all relevant information that will assist the nurses to acquire the depth knowledge regarding morphological features of bacteria and its subject matter...............

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Bacterial morphology

  1. 1. Living material is organized in unit and microorganism were living form of microscopical size and usually unicellular in structure originally organization is unsatisfied.
  2. 2. 3
  3. 3. 4 Bacterial Cell
  4. 4.  Unicellular  Circular DNA  No organelles  1/10th the size of eukaryotic cells  Flagella-long hair-like structure used for movement  Reproduce asexually –Binary Fission
  5. 5.  Size of bacteria:  Bacteria are so small because of that their size is measured in a micron (u )  Generally cocci are about 1u in diameter and bacilli are 2 to 10 u in length and 0.2 to 0.5 u in width  The limit of resolution with unaided eye is about 200 u because of that bacteria can be only visualized under microscope.
  6. 6.  Shape of bacteria:  Cocci in cluster – staphylococci  Cocci in chain – streptococci  Cocci in pair- diplococci  Cocci in group of four – tetrad  Cocci in group of eight – sarcina
  7. 7. • In the bacteria the outer layer or cell envelop or bacteria consist of two things (a) rigid cell wall (b) underlying cytoplasmic membrane or plasma membrane: it includes granules, ribosomes, mesosomes and circular DNA.  Some bacteria in addition to possess aditional structures such as gelatinous material which cover it is called as capsule and when it is too thin it is called as microcapsule.
  8. 8.  Flagella  Pili  Capsule  Plasma Membrane  Cytoplasm  Cell Wall  Lipopolysaccharides  Teichoic Acids  Inclusions  Spores Chapter 4
  9. 9.  Introduction: most cell posses a cell envelop consisting of cell wall and underlying cytoplasmic membrane.  Definition: “the tough, rigid structure which surrounds bacterial cell it is called as cell wall” • Thickness: 10-20nm • Weight: 20-25% of dry weight of bacterial cell wall
  10. 10. Chapter 4 Chemical structure of cell wall:  Chemical structure of cell wall is made up of a Peptido- glycan Polymer (amino acids + sugars)  That structure is unique to all bacteria  Sugars; NAG & NAM  N-acetylglucosamine  N-acetymuramic acid  Amino acids cross link NAG & NAM
  11. 11.  Made of peptidoglycan – a combination of protein and polysaccharides  It is present in both gram positive & negative bacteria.  Some bacteria called Gram negative bacteria have an additional layer of membrane that contains lipopolysaccharide - this extra layer inhibits the uptake of antibiotics – protecting the bacteria cell membrane cell wall cell membrane Outer membrane lipopolysaccharide cell wall
  12. 12.  Gram negative cell wall:  Lipoprotein layer: it connects the peptidoglycan to outer membrane  Outer membrane : this contain certain proteins that work as a target sites for antibiotics.  Lipopolysaccharide : it consist endotoxins ( which are responsible for pyrogenecity, lethal effect, tissue necrosis)
  13. 13.  Periplasmic space : it is the space between inner & outer membrane which contains important proteins and oligosaccharides.
  14. 14. Gram positive cell wall:  Peptidoglycan layer : in gram positive bacteria peptidoglycan layer is thicker( 15-25 nm ) than gram negative bacteria ( 10-15 nm )  Gram positive cell wall contains antigens such as polysaccharide & proteins.
  15. 15.  Function  1) protection of internal structure  2)Gives shape to the cell  3) confers rigidity & ductility  4) role in division of bacteria  5) offers resistance to harmful effect of environment.  6) contains receptor sites for antibiotics  7)Provide attachment to complement
  16. 16. Gram positive Vs gram negative
  17. 17. Chapter 4
  18. 18. Chapter 4
  19. 19. Difference Gram positive Gram negative 1. Thickness 15-25 nm 10-15 nm 2. variety of amino acid Few Several 3. aromatic & sulfar containing amino acid Absent Present 4. Lipid Low 2-4 % High 15-20 % 5. Teichoid acid Present Absent 6. Periplasmic space Absent Present 7. result of enzyme digestion Protoplast Spheroplast
  20. 20. Absorb stain appear purple Don’t absorb stain appear pink The type of cell wall is used by doctors to help diagnose disease The bacteria are stained with a special stain called Gram stain Bacteria without the extra membrane, appear purple. These are Gram positive (Gram +) bacteria bacteria with the extra membrane appear pink. These are Gram negative ( Gram -) bacteria
  21. 21. Chapter 4
  22. 22.  Definition: “thin semipermiable membrane which lies just beneath the cell wall that is called as cyto plasmic membrane”  The whole bacterial cytoplasm is bound peripherally by very thin,elastic and semipermiable cytoplasmic membrane also known as cell membrane.  It is 5-10nm in width  Electron microscope shows the presence of three layer constituting a unit membrane structure.
  23. 23.  Chemically the membrane consist of phospholipid with small amount of protein. Sterol is absent except in mycoplasma.  DEMONSTRATION:  The seperation of membrane from cell wall is achived by readily in gram negative bacteria when they are suspended in medium of high osmotic tension.such phenomenom is called as plasmolysis  Electron microscope
  24. 24. Chapter 4
  25. 25. Chapter 4
  26. 26.  Transport: (1) Active transport: it is site of numerous enzymes (oxidase polymerase, permease) involved in the active transport of selective nutrients. It is impermiable to macromolecule nd ionised substances. (2) Passive transport: It is act as semipermiable membrane through inward and outward passage of water and passive trnsport of molecule lipid soluble solutes take place by diffusion
  27. 27. (2) Concentration: it is also concentration sugar, amino acids and phosphate so that a 300-400 fold grandient exists across osmotic barrier. (3) Enzymatic function: it also contain cytochrome oxidase, enzyme of tricarboxylic acid cycle and polymerising enzyme necessary for synthesis of cell wall
  28. 28. “Bacterial cytoplasm is suspension of organic and inorganic solutes in viscous watery solution”  It is not exhibiting protoplasmic streaming and it lacks endoplasmic reticulum or mitochondria. It contains ribosomes, mesosomes, inclusion and vacuoles.  All the organills which cytoplasm contains is as follows.
  29. 29. (1) Ribosomes: Ribosomes appear as small granules and pack the whole cytoplasm. These are strung together on strands of mRNA to form polymers. the code of mRNA is translated in to peptides sequence t this place. The ribosomal particles become linked up and travels along the mRNA strand. Function: Site for protein synthesis.
  30. 30.  Polysomes: They are the group of ribosomes linked together like beads of chain by messanger RNA  Mesosomes: They are vesicular, convulated or multilaminted structures formed as invagination of plasma membrane in cytoplasm . They are more prominent in the gram positive bacteria.
  31. 31.  Two types of mesosomes (a) septal mesosomes: It is attached to bacterial chrosome nd involved in dna segregation and in formation of cross wall during cell division. (2) Lateral mesosomes: They are at lateral side Functions:  They are site of respiratory enzymes  Coordinate nuclear and cytoplasmic membrane division during binary fission  Responsible for compartmenting DNA at sporulation
  32. 32. “ It is an outer covering of thick jelly like material that surrounds the bacterial cell wall”  Width: 0.2 micrometer  Contains about 90% water and 2% solid  The solid constitutes may be complex polysccharide (pneumococcus klebsiella, enterobacter) or polypeptides (anthrax bacillus) or hyaluronic acid (streptococcus)
  33. 33.  Demonstration: the capsule is best seen in pathological specimens like pus, blood, sputum, and exudates (1) By ordinary stain (gram or acid fast) capsule can not be stained, it apper as halo arround the stained bacterial body. (2) In negative staining (india pink preparation), capsule appears as clear halo around the bacterium as link can not penetrate capsule.
  34. 34.  Immunological method: in that stained with antiserum that swallowed by capsule so it appear as swollen under microscope so it is called as capsular awelling reaction. E.g pneumococcus  Capsulated organism: s.pneumoniae,Bacillus anthracis, C.perfringes, pneumobacillus, H.influenzae
  35. 35.  Capsule serve as protective covering against antibacterial substances such as bacteriophase, phagocytes and enzymes  Enhance bacterial virulance  Capsular antigen is hapten in nature and specific for bacteria.
  36. 36.  Definition  “These are long, sinnous contractile filamentous appendages known as f lagella”.  Composed of a flagellin subunit.  Usually sheathed (covered).  Rotates by way of a basal body in the bacterial cell.  Unique to bacteria.
  37. 37.  These are organs of locomotion . ex:-Escherichia coli salmonella, vibrio , pseudomonas, etc.  The number of f lagella varies up to 10 to 20 per cells according to species of bacteria.  These are extremely thin (diameter)12 to 30 nm, helical shaped structure of uniform diameter throughout their length .  these are 3 to 20 nm long.  Each flagellum consist of hook & basal body. It originates in a spherical body located just inside cell wall.
  38. 38. 43
  39. 39.  Composed of filament, hook, and basal body  Flagellin protein (filament) is deposited in a helix at the lengthening tip  Base of filament inserts into hook  Basal body anchors filament and hook to cell wall by a rod and a series of either two or four rings of integral proteins  Filament capable of rotating 360º
  40. 40.  Arrangement/ types  Monotrichous; 1 flagella  Lophotrichous; tuft at one end  Amphitrichous; both ends  Peritrichous; all around bacteria Chapter 4
  41. 41. Function  It is responsible for bacterial motility.- Motility may be observed microscopically or by  detecting the spreading growth in semi solid agar medium. Demonstration –  Dark ground microscopy.  Special staining techniques in which their thickness is increased by mordanting.  Electron microscop.  Hanging drop preparation.
  42. 42.  Definition  “Fimbria are filamentous , short , thin , straight , hair like appendage”.  This is 0.1 to 1.5 µ long & less than 4 to 8 nm thick.  They are also called as Pili.  Fimbriae are seen only in some gram negative bacteria.  Each bacterium may have 100 to 500 Fimbriae on all over the body of bacteria.  They project from cell surface as a straight filaments.  They are best developed in freshly isolated strains & in liquid culture.  They are composed of protein known as pillin (molecular weight 18000 Daltons).
  43. 43. Different forms of fimbria –  i)common pili  ii)F (fertility) pili  iii) Col I (colicin)pili
  44. 44. DEMONSTRATION:-  Electron microscop.  Hem agglutination.  Fimbriated bacteria form pellicle in liquid media. FUNCTION:-  a) Organ of adhesion.  b) Hem agglutination.  c) They are antigenic.  d) Agglutination & pellicle formation.  e) Genetic material is transferred from the donor to recipient cell.
  45. 45. Sr.n o Flagella Fimbriae 1 Size larger & thicker Smaller & thinner 2 Arise from cytoplasm or cytoplasmic membrane but does not attached to cell wall Attached to cell wall 3 Organ of movement (locomotion) Organ of adhesion & conjugation 4 They are never straight They are alwase strait
  46. 46. “ spores are highly resistant dormant stage of bacteria formed in unfavourble environmental condition such as starvation and dessication”  As spores are formed within the parent bacterial cell so they are also called as endospores  During germination each spore give rise to only one vegetative bacteria  Exospores found in fungi(conidia) formed extracellularly from end of parent cells.  Sporulation is not a method of reproduction
  47. 47. A. Gram positive bacilli: (1) obliterate aerobic- genus bacillus.e.g B.anthracis, B.subtilis (2) obliterate anaerobic:genus clostridia.e.g C.tetani, C.welchii, C.botulism B. Other bacteria: Gram positive coccus (porosarcina) gram negative bacilli (coxiella burnetii)
  48. 48.  The cell membrane grows inward and forms spore wall around the core (forespore). The inner-most layer of the spore wall forms the spore membrane from which the cell wall of future vegetative bacterium develops. Outside this membrane is thick layer, the cortex and a multilayered tough spore coat. Some spores have an additional apparently rather loose, outercovering called exosporium.
  49. 49. spontaneous sporulation occurs in condition unfavourable condition such as starvation, dessication, presence of disinfectants and in extreme temperature.
  50. 50. 58http://www.microbe.org/art/endospore_cycle.jpg
  51. 51. Spore formation is initiated by apperance of clear area in portion of protoplasm near one end of bacterial cell and that protoplasm gradually become more opaque that form forespore The cell membrane grow inwards and undergoes infolding forming double layered membrane structure around the core The inner most layer of spore wall forms spore membrane in future vegetative bacterium will develop. The spore wall synthesis a thick covering lyer cortex and multilayered thin but tough outer layer spore coat
  52. 52. Spores of some spesis have additional apparently rather loose outer covering called exosporium Spore cortex contains unusual type of peptidoglycan sensetive to lysosomes the spore cot is made up of keratin which is impervious to antibacterial chemical agent Exosporium is a lipoprotein membrane with some carbohydrate residue. Young spores remain attached to parent cell
  53. 53.  The young spore remain attached t parant cell. The precise position and shape and relative size of spores remain constant within particular bacteria.  Spore may be central,sub terminal or terminal
  54. 54.  Bacterial spores are resistant to ordinary boiling, heating, and disinfectant. They can withstand boiling up to 3 hr, dry heat at 150c for 1 hr however they are destroyed by autoclaving at 121c for 15-20 min.  The highly impervious spore coat, low water content, low metabolic activity and high concentration of calcium dipicolinate of spore make resistant to drying and heat.
  55. 55.  Definition: “ The process of conversation of spore in to vegetative cell under suitable environment is known as germination” There are three stages of germination
  56. 56.  The germintion of bacterial spore do not occur even when placed in environment that favour process.  Unless first activated by one or onother agent damage the coat of spore such as heat, abration and compound containing free sulphydryl groups.
  57. 57.  The process of initiation is not clear, however the spore will initiate germination in favourable condition.  Different species of bacteria recognizes different effactors as signalling a rich medium such as L-alanine for one spesis
  58. 58.  With the swelling of spore wall and disintegration of cortex a single germ cell emerge after breaking open the spore coat.  The new vegetative cell consist of spore protoplast with its surrounding wall.  Formation of vegetative cell.
  59. 59.  By ordinary stain and modified Z-N stain.  Laboratory: for making sterilization
  60. 60. Chapter 4
  61. 61.  Pili – hairlike structures usually found in Gram neg. bacteria. Help the bacteria stick to surfaces. Also forms conjugation bridge  Chromosome – a single loop of DNA that is folded on itself - controls the cell’s function  Nucleoid – the region of the cytoplasm where the DNA is found  Plasmid – an accessory loop of DNA – small contains only a few genes - can be responsible for: conjugation, antibiotic resistance, unique metabolic properties – like the ability to use hydrocarbons  Capsule – found outside some bacteria stores nutrients and protects the bacteria from changing environmental conditions
  62. 62.  Short protein appendages  smaller than flagella  Adhere bacteria to surfaces  E. coli has numerous types  K88, K99, F41, etc.  Antibodies to will block adherance  F-pilus; used in conjugation  Exchange of genetic information  Flotation; increase boyancy  Pellicle (scum on water)  More oxygen on surface Chapter 4
  63. 63. Chapter 4

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