Bacterial morphology

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

1. BACTERIA

2. INTRODUCTION Living material is organized in unit and microorganism were living form of microscopical size and usually unicellular in structure originally organization is unsatisfied.

3. Prokaryotic & Eukaryotic Cells 3

4. 4 Bacterial Cell

5. Bacteria Characteristics Unicellular Circular DNA No organelles 1/10 th the size of eukaryotic cells Flagella-long hair-like structure used for movement Reproduce asexually –Binary Fission

6. Size & shape of bacteria : 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.

7. 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

8. Morphology of bacteria Maulik :

9. Bacterial anatomy (structure) 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.

10. Bacterial Structures Flagella Pili Capsule Plasma Membrane Cytoplasm Cell Wall Lipopolysaccharides Teichoic Acids Inclusions Spores Chapter 4

11. CELL WALL 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” T hickness: 10-20nm Weight: 20-25% of dry weight of bacterial cell wall

12. 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

13. Bacterial Structure: Cell Wall 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 li popolysaccharide cell wall

14. 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)

15. Periplasmic space : it is the space between inner & outer membrane which contains important proteins and oligosaccharides.

16. 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.

17. 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

18. Gram positive Vs gram negative

19. Chapter 4

20. Chapter 4

21. 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

22. Gram + vs. Gram - 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

23. Chapter 4

24. Cytoplasmic membrane 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.

25. 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

26. Chapter 4

27. Chapter 4

28. Function 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

29. (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

30. Cytoplasm “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.

31. 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.

32. 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.

33. 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

34. Bacterial capsule “ 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)

35. Demonstration: the capsule is best seen in pathological specimens like pus, blood, sputum, and exudates By ordinary stain (gram or acid fast) capsule can not be stained, it apper as halo arround the stained bacterial body. In negative staining ( india pink preparation), capsule appears as clear halo around the bacterium as link can not penetrate capsule.

36. 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

37. Function 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.

38. Flagella 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 .

39. 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.

40. 43

41. Bacterial Flagella Structure 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

42. Arrangement/ types Monotrichous ; 1 flagella Lophotrichous ; tuft at one end Amphitrichous ; both ends Peritrichous ; all around bacteria Chapter 4

43. 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.

44. Fimbria ( Pili ) 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).

45. Different forms of fimbria – i)common pili ii)F (fertility) pili iii) Col I ( colicin ) pili

46. 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.

47. Difference between flagella & fimbriae. Sr.no 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

48. SPORES “ 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

49. Spore forming bacteria 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 )

50. Spore morphology

51. Morphology of spore. 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 .

52. Shape & position of spore.

53. Sporogenesis spontaneous sporulation occurs in condition unfavourable condition such as starvation, dessication , presence of disinfectants and in extreme temperature.

54. Endospore formation 58 http://www.microbe.org/art/endospore_cycle.jpg

55. SPOROGENESIS PROCESS

56. Conti……

57. Shape and position 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

58. Resistance 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.

59. Germination Definition: “ The process of conversation of spore in to vegetative cell under suitable environment is known as germination” There are three stages of germination

60. 1. Activation 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.

61. 2.Initiation 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

62. Out growth 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.

63. Demonstation By ordinary stain and modified Z-N stain. Laboratory: for making sterilization

64. Chapter 4

65. Bacterial Structure continued 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

66. Pili 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

67. F-Pilus for Conjugation Chapter 4