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2. Prokaryotic and Eukaryotic cell structure.pptx

  1. Prokaryotic and Eukaryotic cell  All living cells can be classified as  Prokaryotic cells:  the Greek words pro (before) and karyon (nucleus).  cells lack a nucleus and other membrane-enclosed structures.  All prokaryotes are:  single-celled organisms, and all are bacteria.  Eukaryotic cells:  eu (true) and karyon (nucleus).  cells have a true nucleus and membrane-enclosed structure. 4/1/2023 1
  2. Cell types …  Eukaryotes include all  plants, animals, fungi, and protists.  Prokaryotic and eukaryotic cells are similar in several ways.  Both are surrounded by a cell membrane, or plasma membrane.  encode genetic information in DNA molecules. 4/1/2023 2
  3. Similarities and Differences Between Prokaryotic and Eukaryotic Cells Characteristic Prokaryotic Cells Eukaryotic Cells Genetic material (DNA) single circular DNA Paired linear DNA Location Nuclear region (nucleoid) Membrane-enclosed nucleus Nucleolus Absent present Histone proteins Absent Present Extrachromosomal DNA Plasmids Mt and chloroplasts Membrane bounded organelles Absent Present: ER, Mt, GA etc. Respiratory enzymes Cell membrane Mitochondria Ribosomes 70S 80S in cytoplasm and on rER, Cell wall PG found on most cells Cellulose, chitin, mannan,glucan Cell division Binary fission Mitosis and/or meiosis Reproduction Asexual Sexual or asexual reproduction 4/1/2023 3
  4. Prokaryotes cells…  Bacteria are prokaryotic, single-celled microorganisms. Have a complex cell wall and Have a single, Ds ,circular DNA lack a nuclear membrane Reproduce by Binary fission Metabolically they are active and mostly independent 4/1/2023 4
  5. Bacterial Taxonomy  Taxonomy: is the formal system for organizing, classifying, and naming living things.  Classification: is the assignment of organisms (species) based on evolutionary relationships  Nomenclature:  Identification:  The Levels of Classification: Hierarchy  It begins with domain, and ends with species, the smallest and most specific taxon.  Assigning Specific Names: Linnaeus (1701-1778)  The binomial system of nomenclature describes each living organism 4/1/2023 5
  6. Classification …  Binomial nomenclature includes: i. Genus comes before species (e.g., Escherichia coli) ii. Genus name is always capitalized (e.g., Escherichia) iii. Species name is never capitalized (e.g., coli) iv. Both names are always either italicized or underlined ( e.g Escherichia coli ) v. The genus name may be used alone, but not the species name (i.e saying or writing “Escherichia “ alone is legitimate while saying or writing “ coli” is not) 4/1/2023 6
  7. Classification…  In general, Bacterial classification depends on:  Phenotypic methods 1. Morphology and arrangement 2. Staining 3. Anatomic structures 4. Physiology Cultural characteristics Biochemical reactions Antigenic structure  Genetic :Base composition of bacterial DNA DNA-DNA hybridization rRNA G+C Content 4/1/2023 7
  8. Morphology of Bacteria Size Prokaryotes are among the smallest of all organisms. Most prokaryotes range from 0.5 to 2.0 um in diameter. With some exception cyanobacteria are 60 um long Bacillus anthrax measures 10um 4/1/2023 8
  9. Morphology of Bacteria Shape 1. Spherical /circular Coccus/Cocci Plane of division I. Pairs diplococci one II. Four cells arranged tetrad two III. Eight cells arranged Sarcina three IV. Chains streptococci one V. Clusters staphylococci Random 4/1/2023 9
  10.  Arrangement of bacterial cells 4/1/2023 10
  11. Morphology of Bacteria 2. Rod –shaped Bacilli/bacillus Bacilli divide in only one plane. Diplobaccilli or Streptobacilli Straight Curved/comma-shaped tapered-fusiform Cocc-bacilli-short rods Pleomorphic Vibrio 4/1/2023 11
  12. 4/1/2023 12
  13. Morphology of Bacteria 3. spiral shaped: (spirochetes)  Spiral bacteria are not generally grouped together.  Spirillum spirochetes  Color  Bacteria are colorless, transparent(similar refractive index with surrounding environment).  Staining preparation needed to see them under the microscope. 4/1/2023 13
  14. Staining characteristics 4/1/2023 14  Gram positive vs. gram negative bacteria  Acid fast positive vs. negative bacteria
  15. 4/1/2023 15 Typical bacterial cell structure Bacterial cell structure
  16. Bacterial structure  Bacterial structure 4/1/2023 16
  17. Bacterial cell Structure 1. Surface layers (capsule, loose slime) 2. Surface appendages (Pilli, flagella) 3. Cell envelope (Cell wall , Cell membrane ) 4. Internal structures (nucleoid, cytoplasm, plasmid, ribosomes, mesosomes, endospores etc.) 4/1/2023 17  External structures
  18. 1. Surface appendages (Pilli, flagella)  Are surface structures originated outside the CM  Sometimes being attached to it, and  Extended into the environment  Two types of surface appendage are found on certain bacterial species: 4/1/2023 18
  19. Surface appendages… 4/1/2023 19 I. Flagella : Are thread/whip like structures Free at one end and attached to a cell at the other end made of protein flagellin. are organs of locomotion  occur on both Gram-+ve and Gram-ve bacteria.  Their presence can be useful in identification.  Flagellar antigen-H antigen
  20. Flagella… 4/1/2023 20  The flagella has 3 basic parts  The filament-the long outermost region. -Consists of flagellin a Globular protein. The hook-where the filament is attached -wider and consists of different proteins. The basal body-which anchors the flagellum to the CW and CM. -composed of a small central rod inserted into a series of rings. -in GNB, it contains two rings -the outer pair of ring is anchored to the CW. -the inner pair of rings is anchored to the CM -In GPB, only the inner pairs of rings are
  21. Flagella… 4/1/2023 21  Structure of prokaryotic
  22. Surface appendages… Flagellar arrangements 1. Atrichous: Bacteria with no flagellum. 2. Polar 2.1. Monotrichous: Bacteria with single polar flagellum. 2.1. Lophotrichous: Bacteria with bunch of flagella at one pole. 2.3 Amphitrichous: Bacteria with flagella at both poles. 3. Peritrichous: Bacteria with flagella all over their surface. 4/1/2023 22
  23. Flagelar arrangement Typical arrangements of bacterial flagella. 4/1/2023 23
  24. Flagella…  Function Locomotion/movement (motile vs. non-motile) Colonization/attachment Antigenic-flagellar antigen “H” antigen Serogrouping/serotyping 4/1/2023 24
  25. ii. Fimbriae and Pili  Hairlike appendages common in GNB.  Are shorter, straighter and thinner than flagella.  Used for attachment and transfer of DNA.  composed of protein called pilin.  pili occur almost exclusively on Gram-negative bacteria.  found on only a few GPB(e.g., Corynebacterium renale).  Pili (Latin hairs), fimbriae (Latin fringes). 4/1/2023 25
  26. Pili and Fimbriae…  Two types (Based on function)  Common pili(Fimbriae):  A few to several hundreds per cell.  Have the tendency to adhere to each other and to the surface.  The structure for adherence to cell to cell surface.  They involved in biofilm formation.  Help bacteria to adhere epithelial cells 4/1/2023 26
  27. Pili and Fimbriae.. 4/1/2023 27  Sex pili:  Are usually longer than fimbriae  Only 1 or 2 in numbers per cell.  Involved in motility and transfer of genetic material during the process of conjugation.  Twitching and gliding motility
  28. Comparison between flagella and Pili 4/1/2023 28
  29. Cell envelopes(cell wall, cell membrane )  Cell wall:  a rigid, multilayered structure  Non -selectively permeable  Almost exclusively common in all bacterium except Mycoplasma spp., protoplasm  Contain somatic antigen “O” Ag.  Made up of a polymer of peptidoglycan (murein):  N-acetyl glucosamine( NAG)  N-acetyl muramic acid (NAM)  Four aa attached on NAM as side chain 4/1/2023 29
  30. Cell wall… L-alanine D-alanine D-glutamic acid Diaminopimelic (DPA)-lysine  A set of identical peptide bridge cross links NAG with NAM with the help of carboxypeptidase and transpeptidase enzymes. 4/1/2023 30
  31. Cell wall…  Components of cell wall of Gram positive bacteria 1. Peptidoglycan 2. Teichoic acid  Components of cell wall of Gram negative bacteria 1. Peptidoglycan 2. Lipoprotein 3. Phospholipid 4. Lipopolysaccharide 4/1/2023 31
  32. GPB vs. GNB Cell Wall 4/1/2023 32
  33. GPB vs. GNB Cell Wall 4/1/2023 33
  34. Cell wall defective bacteria I. Natural: e.g. Mycoplasma species II. Induced:  produced after exposure of antibiotics, detergents, lysozymes 1. Protoplasm:  a bacterial cell with its cell wall completely removed .  It is spherical in shape and osmotically sensitive (gram +ve) 2. Spheroplast :  a relatively spherical cell formed by the weaking or partial removal of cell wall component  e.g by penicillin tx of gram –ve . 4/1/2023 34
  35. Cell wall defective bacteria 3. L-forms:  are (G+ve and -ve mutant bacteria) partial or complete loss of the cell wall. Resistance to antibiotics Can grow and divide Encounter infections Can revert to the normal form 4/1/2023 35
  36. Functions of cell wall 1. Provides shape to the bacterium 2. Gives rigidity to the organism 3. Protects from environment 4. Provides staining characteristics to the bacterium 5. Contains receptor sites for phages/complements 6. Site of action of antibody, antibiotics and colicin 7. Contains toxic components to host-endotoxic 4/1/2023 36
  37. Cell /plasma membrane  Phospholipid by layer +protein  It accounts for 30% of the dry weight of bacterial cell.  It is composed of  60% protein  20-30% lipids and  10-20% CHO Function of cell membrane 1. Selective permeable/barrier 2.Transport of molecules(passive, active) 3. Energy generation: Respiration –ATP 4. Synthesize biosynthetic enzymes 4/1/2023 37
  38. Surface layers 4/1/2023 38  Glycocalyx :  Secreted substance on the surface of many prokaryotic cells.  A.k.a the pericellular matrix- substances that surround cells  Glycocalyx (meaning sugar coat)  It is a viscous (sticky), gelatinous polymer  It is composed of polysaccharide, polypeptide, or
  39. surface layers  Capsule:  Glycocalyx which is organized and is firmly attached to the cell wall the outer most layer of bacteria cell.  made of polymers of polysaccharide +polyalcohols+aminosugars except in B.anthracis (polymers of D-glutamic acid). capsulated bacteria produced smooth, mucoid colonies. Non-capsulated bacteria produced rough non-mucoid colonies. Capsular antigens, K,Vi e.g. Hameophilus influnzae ,S.pneumoniae, N.meningitis 4/1/2023 39
  40. function of capsule  Anti-phagocytic Activity  Antigenicity  Attachment/adherence/colonization  Resistance to drying  Serotyping bacteria 4/1/2023 40
  41. Surface layer… 4/1/2023 41  Slime layer Glycocalyx substance is unorganized and only loosely attached to the cell wall. The Glycocalyx is a very important component of biofilms.
  42. Mesosomes  Infoldings/invagination of the plasma membrane in which bacterial chromosomes attached to it.  Often found near dividing line in bacteria  Involved in segregation of newly replicated chromosomes following DNA replication. 4/1/2023 42
  43. Internal structures 4/1/2023 43  Ribosomes  DNA(Nucleoid)  Granules  Plasmid  Endospores Polyamine Cytoplasmic constituents
  44. Inclusion bodies /granules  Aggregates of various compounds used as foods storage /reserves Poly-beta hydroxyalkanoate (PHA): is a derivative of poly-hydroxybutyrate (PHB): source of carbon and energy Metachromic granules (volutin): inorganic sulphate, Sulfur granules Polysaccharide granules : usually glycogen or starch Lipid inclusions 4/1/2023 44
  45. Endospores  Small round, highly resistant, resting structures produced with the cell during starvation/accumulation of toxic wastes.  Little or no metabolism inside the spore  Spores are resistant to heat, radiation, chemicals and desiccation  Spores are cable of detecting their environment and under favorable environmental conditions.  they germinate and retuning to the vegetative state  Spore formation (sporulation)-process of forming spores 4/1/2023 45
  46. Layers of endospore Core: the core is dehydrated cytoplasm; containing DNA, ribosomes ,enzymes ,calcium dipocolinate (5-15% of dry weight). Cortex: the cortex is a modified cell wall/PG layer. Coat: keratin-like proteins layers that are impermeable to most chemicals 4/1/2023 46
  47. Structure of bacterial endospore 4/1/2023 47 Structure of bacterial endospore o Are formed in response to certain adverse nutritional conditions. o Are inactive bacterial cells. o More resistant to desiccation, heat and various chemicals. o Contain calcium dipicolinate which aids in heat resistance within the core. o Germinate under favorable nutritional conditions. o Helpful in identifying some species of bacteria. o Spore germinate to produce a single vegetable cell.
  48.  Arrangement of spore/location  Terminal  Central  Subterminal  Spore former bacteria Clostridium spp Bacillus spp. Coxiella burnetti 4/1/2023 48
  49. Germination of spores  The overall process of converting a spore into a vegetative cell.  It has three stages: Activation, germination proper and outgrowth. Activation: favorable environmental condition Initiation: degradation of the cortex PG and release of calcium dipocolinate from the core. Outgrowth: forming new vegetative cells 4/1/2023 49
  50. 4/1/2023 50 Germination… A typical sporulation cycle from the active vegetative cell to release and germination
  51. Bacterial Nutrition and Growth  Bacterial nutrition:  Bacteria, like all cells, require nutrients for the maintenance of their metabolism and for cell division.  Bacterial structural components and the macromolecules for the metabolism are synthesized from the elements.  The four most important elements of bacteria are C, H2, O2 and N2.  Minerals: sulfur and phosphorus, trace elements 4/1/2023 51
  52. 4/1/2023 52
  53. Carbon  Organisms require a source of carbon for the synthesis of numerous organic compounds that comprise protoplast.  Depending on their requirements, bacteria can be classified as 1. Autotrophs: Free-living, non-parasitic bacteria  use carbon dioxide as carbon source.  The energy needed for their metabolism can be obtained from: 4/1/2023 53
  54. 2. Heterotrophs: Parasitic bacteria require more complex organic compounds as their source of carbon and energy. Human pathogenic bacteria are heterotrophs The principal source of carbon is CHO which are  degraded either by oxidation, in the presence of oxygen, or  by fermentation, in the absence of oxygen, to provide energy in the form of ATP. 4/1/2023 54
  55. 4/1/2023 55  Glycolysis  Pyruvic Acid  Fermentation  Aerobic respiration
  56. 4/1/2023 56 The main types of energy-capturing metabolism.
  57. Terms Relating to Energy and Carbon Sources 4/1/2023 57
  58. Bacterial Nutrition…  Hydrogen and oxygen  Obtained from water.  Essential for the growth and maintenance of cell.  Nitrogen Constitutes 10% of dry weight of bacterial cell. Obtained from organic molecules like proteins and inorganic molecules like ammonium salts and nitrates. 4/1/2023 58
  59. Growth factors  Growth factors are organic compounds Required in small amounts the cell can not synthesize from other carbon source.  These are aminoacids, purines and pyrimidines, and vitamins.  Prototrophs: Wild-type bacteria with normal growth requirements.  Auxotrophs: Mutant bacteria, which require an 4/1/2023 59
  60. BACTERIAL GROWTH  It is an orderly increase in all the components of an organism.  It is an increment in biomass.  It is synchronous with bacterial cell reproduction. Generation time: is the time taken for the size of a bacterial population to be double. Bacterial growth phases  The normal bacterial growth curve has four phases. Lag phase Exponential(log) phase Maximal stationary phase Decline phase 4/1/2023 60
  61. 1. Lag phase  The period of adaptation  active macro molecular synthesis like DNA, RNA, various enzymes and other structural components.  It is the preparation time for reproduction; no increase in cell number. 4/1/2023 61
  62. 2. Exponential(log) phase 4/1/2023 62  The period of active multiplication of cells.  Cell division precedes at a logarithmic rate. determined by the medium and condition of the culture.
  63. 3. Maximal stationary phase  The period when the bacteria have achieved their maximal cell density or yield.  There is no further increase in viable bacterial cell number.  The growth rate is exactly equal to the death rate. A bacterial population may reach stationary growth when one of the following conditions occur:  The required nutrients are exhausted 4/1/2023 63
  64. 4. Decline phase  The period at which the rate of death of bacterial cells exceeds the rate of new cell formation.  There is drastic decline in viable cells.  Few organisms may persist for so long time at this period at the expense of nutrients released from dying micro- organisms. 4/1/2023 64
  65. 4/1/2023 65
  66. Factors influencing bacterial growth  Rates of bacterial growth are influenced by the following environmental parameters. I. Nutrition II. Temperature III. Oxygen IV. PH V. Salinity 4/1/2023 66
  67. 1. Nutrition  Macromolecules (source of C,H,O,N)  Minerals: sulfur and phosphorus, trace elements  Growth factors: amino acids, purines, pyrimidines and vitamins. 4/1/2023 67
  68. 2. Temperature  Optimal growth range of temperature: The temperature at which the maximum growth rate occurs; and results in the shortest generation time of bacteria. Optimal growth temperature Psychrophilic bacteria:15-20 ° c; grow best at low T° range Mesophilic bacteria:30-37 °c; grow best at middle T° range 4/1/2023 68
  69. Optimal temperature required of bacteria 4/1/2023 69
  70.  Base on oxygen requirements and tolerance, bacteria are classified as: 1. Obligate aerobes 2. Microaerophilic 3. Obligate anaerobes 4. Facultative anaerobes 5. Aerotolerent anaerobes 6. Capnophilic 3. Oxygen 4/1/2023 70
  71.  Obligate aerobic bacteria grow only when free oxygen is available to support their respiratory metabolism.  They obtain ATP by using oxygen as a final electron acceptor in respiration.  Obligate anaerobic bacteria grow in the absence of oxygen; exposure to oxygen kills anaerobes.  FA bacteria: grow in the presence or absence of O².  They obtain ATP by fermentation or anaerobic respiration. 4/1/2023 71
  72. Environmental oxygen… 4/1/2023 72  Microaerophilic bacteria grow best at reduced oxygen tension; high oxygen tension is toxic to them.  Aerotolerant anaerobes do not utilize oxygen but can survive in its presence.  are not killed by oxygen, because they possess alternative mechanisms for breaking down peroxides and superoxide.  Capnophilic bacteria grow best at a higher
  73. Environmental oxygen… 4/1/2023 73 Bacterial growth at different environmental oxygen concentration
  74. 4.Hydrogen ion concentration  Neutrophilic bacteria grow best at near neutral PH value.  Acidophilic bacteria prefer to grow at low PH value (acidic medium).  Alkalophilic bacteria prefer to grow at high PH value (alkaline medium).  Most pathogenic bacteria grow best at PH of 6-8. 4/1/2023 74
  75. 5. Salinity  Salt content of the medium affects bacterial growth.  Halophile bacteria grow best at high salt concentration.  Moderate halophiles: require 3% salt concentration.  Extreme halophiles require 15% salt concentration.  Most bacteria can not tolerate high salt concentration. 4/1/2023 75
  76. 4/1/2023 76