1. II. Cells of Bacteria and Archaea 2.5Cell Morphology 2.6Cell Size and the Significance of Being Small

2. 2.5 Cell Morphology Morphology = cell shape Major cell morphologies (Figure 2.11) –Coccus (pl. cocci): spherical or ovoid –Rod: cylindrical shape –Spirillum: spiral shape Cells with unusual shapes –Spirochetes, appendaged bacteria, and filamentous bacteria Many variations on basic morphological types

3. Figure 2.11 Coccus Rod Spirillum Spirochete Stalk Hypha Filamentous bacteria Budding and appendaged bacteria

4. 2.5 Cell Morphology Morphology typically does not predict physiology, ecology, phylogeny, etc. of a prokaryotic cell May be selective forces involved in setting the morphology –Optimization for nutrient uptake (small cells and those with high surface-to-volume ratio) –Swimming motility in viscous environments or near surfaces (helical or spiral-shaped cells) –Gliding motility (filamentous bacteria)

5. Size range for prokaryotes: 0.2 µm to >700 µm in diameter –Most cultured rod-shaped bacteria are between 0.5 and 4.0 µm wide and < 15 µm long –Examples of very large prokaryotes Epulopiscium fishelsoni (Figure 2.12a) Thiomargarita namibiensis (Figure 2.12b) Size range for eukaryotic cells: 10 to >200 µm in diameter 2.6 Cell Size and the Significance of Being Small

6. 3/r

7. 2.6 Cell Size and the Significance of Being Small Surface-to-volume ratios, growth rates, and evolution –Advantages to being small (Figure 2.13) Small cells have more surface area relative to cell volume than large cells (i.e., higher S/V) »Support greater nutrient exchange per unit cell volume »Tend to grow faster than larger cells

9. Figure 2.12

10. Rickettsia Smallest 0.1  M E. Coli Average Size 0.5 X 1.5  M Epulopisicum fishelsoni 660  M Convoluted Thiomargarita100X (66000  M) Heidi Schulz 1997 Vacuoles ED: Sulfur (S°) TEA: NO 3

11. III. The Cytoplasmic Membrane and Transport 2.7 Membrane Structure 2.8 Membrane Functions 2.9 Nutrient Transport

12. 2.7 Membrane Structure Cytoplasmic membrane –Thin structure that surrounds the cell –Vital barrier that separates cytoplasm from environment –Highly selective permeable barrier; enables concentration of specific metabolites and excretion of waste products

14. 2.7 Membrane Structure Composition of membranes –General structure is phospholipid bilayer (Figure 2.14) Contain both hydrophobic and hydrophilic components –Can exist in many different chemical forms as a result of variation in the groups attached to the glycerol backbone –Fatty acids point inward to form hydrophobic environment; hydrophilic portions remain exposed to external environment or the cytoplasm

15. Figure 2.14 Fatty acids Phosphate Ethanolamine Fatty acids Hydrophilic region Hydrophobic region Hydrophilic region Glycerophosphates Fatty acids Glycerol

16. 2.7 Membrane Structure Cytoplasmic membrane (Figure 2.15) –8–10 nm wide –Embedded proteins –Stabilized by hydrogen bonds and hydrophobic interactions –Mg 2+ and Ca 2+ help stabilize membrane by forming ionic bonds with negative charges on the phospholipids –Somewhat fluid

18. Hopanoid CholesterolSterol All sterols contain the same four rings*

19. 2.7 Membrane Structure Membrane proteins –Outer surface of cytoplasmic membrane can interact with a variety of proteins that bind substrates or process large molecules for transport –Inner surface of cytoplasmic membrane interacts with proteins involved in energy-yielding reactions and other important cellular functions –Integral membrane proteins Firmly embedded in the membrane –Peripheral membrane proteins One portion anchored in the membrane

20. 2.7 Membrane Structure Archaeal membranes –Ether linkages in phospholipids of Archaea (Figure 2.16) –Bacteria and Eukarya that have ester linkages in phospholipids –Archaeal lipids lack fatty acids; have isoprenes instead –Major lipids are glycerol diethers and tetraethers (Figure 2.17a and b) –Can exist as lipid monolayers, bilayers, or mixture (Figure 2.17)

21. Figure 2.16 Ester Ether Bacteria Eukarya Archaea

22. 2.8 Membrane Function Permeability barrier (Figure 2.18) –Polar and charged molecules must be transported –Transport proteins accumulate solutes against the concentration gradient Protein anchor –Holds transport proteins in place Energy conservation –Generation of proton motive force

23. Figure 2.18 Functions of the cytoplasmic membrane Permeability barrier: Prevents leakage and functions as a gateway for transport of nutrients into, and wastes out of, the cell Protein anchor: Site of many proteins that participate in transport, bioenergetics, and chemotaxis Energy conservation: Site of generation and dissipation of the proton motive force

24. 2.9 Nutrient Transport Carrier-mediated transport systems (Figure 2.19) –Show saturation effect –Highly specific

25. Figure 2.19 Transporter saturated Transport Simple diffusion

26. 2.9 Nutrient Transport Three major classes of transport systems in prokaryotes (Figure 2.20) –Simple transport –Group translocation –ABC system All require energy in some form, usually proton motive force or ATP

27. Figure 2.20 Out In R~ 2 3 Transported substance P P ATP ADP + P i Simple transport: Driven by the energy in the proton motive force Group translocation: Chemical modification of the transported substance driven by phosphoenolpyruvate ABC transporter: Periplasmic binding proteins are involved and energy comes from ATP. 1

28. 2.9 Nutrient Transport Three transport events are possible: uniport, symport, and antiport (Figure 2.21) –Uniporters transport in one direction across the membrane –Symporters function as co-transporters –Antiporters transport a molecule across the membrane while simultaneously transporting another molecule in the opposite direction

29. Figure 2.21

30. 2.9 Nutrient Transport The phosphotransferase system in E. coli (Figure 2.22) –Type of group translocation: substance transported is chemically modified during transport across the membrane –Best-studied system –Moves glucose, fructose, and mannose –Five proteins required –Energy derived from phosphoenolpyruvate

31. Figure 2.22 Nonspecific components Specific components Cytoplasmic membrane Out Glucose Direction of glucose transport Glucose 6 _ P P In Direction of P transfer P Pyruvate PE P Enz I HPr Enz II a Enz II b Enz II c P

32. 2.9 Nutrient Transport ABC (ATP-binding cassette) systems (Figure 2.23) –>200 different systems identified in prokaryotes –Often involved in uptake of organic compounds (e.g., sugars, amino acids), inorganic nutrients (e.g., sulfate, phosphate), and trace metals –Typically display high substrate specificity –Gram-negatives employ periplasmic-binding proteins and ATP- driven transport proteins –Gram-positives employ substrate-binding proteins and membrane transport proteins

35. IV. Cell Walls of Bacteria and Archaea 2.10 Peptidoglycan 2.11 LPS: The Outer Membrane 2.12 Archaeal Cell Walls

36. Cell wall characteristics Elastic Confers Rigidity Interior Pressure - Turgor Pressure Permeable to Salts Plasmolysis 10-20 % sucrose Water  Swelling

37. 2.10 Peptidoglycan Species of Bacteria separated into two groups based on Gram stain Gram-positives and gram-negatives have different cell wall structure (Figure 2.24) –Gram-negative cell wall Two layers: LPS and peptidoglycan –Gram-positive cell wall One layer: peptidoglycan

38. Figure 2.24

39. 2.10 Peptidoglycan Peptidoglycan (Figure 2.25) –Rigid layer that provides strength to cell wall –Polysaccharide composed of: N-acetylglucosamine and N-acetylmuramic acid Amino acids Lysine or diaminopimelic acid (DAP) Cross-linked differently in gram-negative bacteria and gram-positive bacteria (Figure 2.26)

40. CELL WALL Procaryotes: GM +peptidoglycan (thick layer) NAG/NAM* GM -peptidoglycan (thin layer) NAG/NAM* Mycoplasma- no cell wall Archaea - lacking peptidoglycan – PTG PTG = protein pseudo-peptidoglycan

41. Figure 2.25 N-AcetylglucosamineN-Acetylmuramic acid (1,4) N-Acetyl group Lysozyme- sensitive bond Peptide cross-links L-Alanine D-Glutamic acid Diaminopimelic acid D-Alanine Glycan tetrapeptide ( M ) ( G )

42. 2.10 Peptidoglycan Gram-positive cell walls (Figure 2.27) –Can contain up to 90% peptidoglycan –Common to have teichoic acids (acidic substances) embedded in their cell wall Lipoteichoic acids: teichoic acids covalently bound to membrane lipids

43. Figure 2.27 Peptidoglycan cable Teichoic acidPeptidoglycan Lipoteichoic acid Cytoplasmic membrane Wall-associated protein

45. 2.10 Peptidoglycan Prokaryotes that lack cell walls –Mycoplasmas Group of pathogenic bacteria –Thermoplasma Species of Archaea

46. 2.11 LPS: The Outer Membrane Total cell wall contains ~10% peptidoglycan Most of cell wall composed of outer membrane, aka lipopolysaccharide (LPS) layer LPS consists of core polysaccharide and O- polysaccharide (Figure 2.28) LPS replaces most of phospholipids in outer half of outer membrane (Figure 2.29) Endotoxin: the toxic component of LPS

47. Figure 2.28

48. Endotoxins Lipid A

49. 2.11 LPS: The Outer Membrane Periplasm: space located between cytoplasmic and outer membranes (Figure 2.29) –~15 nm wide –Contents have gel-like consistency –Houses many proteins Porins: channels for movement of hydrophilic low-molecular-weight substances (Figure 2.29c)

50. 2.11 LPS: The Outer Membrane Structural differences between cell walls of gram-positive and gram-negative Bacteria are responsible for differences in the Gram stain reaction

51. 2.12 Archaeal Cell Walls No peptidoglycan Typically no outer membrane Pseudomurein –Polysaccharide similar to peptidoglycan (Figure 2.30) –Composed of N-acetylglucosamine and N- acetylalosaminuronic acid –Found in cell walls of certain methanogenic Archaea Cell walls of some Archaea lack pseudomurein

52. 2.12 Archaeal Cell Walls S-Layers –Most common cell wall type among Archaea –Consist of protein or glycoprotein –Paracrystalline structure (Figure 2.31)

53. Figure 2.31

54. V. Other Cell Surface Structures and Inclusions 2.13 Cell Surface Structures 2.14 Cell Inclusions 2.15 Gas Vesicles 2.16 Endospores

55. 2.13 Cell Surface Structures Capsules and slime layers –Polysaccharide layers (Figure 2.32) May be thick or thin, rigid or flexible –Assist in attachment to surfaces –Protect against phagocytosis –Resist desiccation

56. Figure 2.32 Cell Capsule

57. 2.13 Cell Surface Structures Fimbriae –Filamentous protein structures (Figure 2.33) –Enable organisms to stick to surfaces or form pellicles

58. Figure 2.33 Flagella Fimbriae

59. 2.13 Cell Surface Structures Pili –Filamentous protein structures (Figure 2.34) –Typically longer than fimbriae –Assist in surface attachment –Facilitate genetic exchange between cells (conjugation) –Type IV pili involved in twitching motility

60. Figure 2.34 Virus- covered pilus

61. 2.14 Cell Inclusions Carbon storage polymers –Poly-β-hydroxybutyric acid (PHB): lipid (Figure 2.35) –Glycogen: glucose polymer Polyphosphates: accumulations of inorganic phosphate (Figure 2.36a) Sulfur globules: composed of elemental sulfur (Figure 2.36b) Carbonate minerals: composed of barium, strontium, and magnesium (Figure 2.37) Magnetosomes: magnetic storage inclusions (Figure 2.38)

62. Inclusion Bodies Organic or Inorganic Bodies Visible by Microscope Organic Inclusion Bodies Glycogen- Carbon storage PHB -Poly-B- Hydroxybutrate Inorganic Compounds Polyphosphate - PP Sulfur-- Granules

64. Figure 2.36 Polyphosphate Sulfur

65. Figure 2.38

66. Figure 2.39

67. Figure 2.40

68. 2.15 Gas Vesicles Molecular structure of gas vesicles –Gas vesicles are composed of two proteins, GvpA and GvpC (Figure 2.41) –Function by decreasing cell density

69. Figure 2.41 Ribs GvpA GvpC

70. 2.16 Endospores Endospores –Highly differentiated cells resistant to heat, harsh chemicals, and radiation (Figure 2.42 ) –“Dormant” stage of bacterial life cycle (Figure 2.43) –Ideal for dispersal via wind, water, or animal gut –Present only in some gram-positive bacteria

71. Figure 2.42

72. Figure 2.43 Vegetative cell Developing endospore Sporulating cell Mature endospore

73. 2.16 Endospores Endospore structure (Figure 2.45) –Structurally complex –Contains dipicolinic acid –Enriched in Ca 2+ –Core contains small acid-soluble spore proteins (SASP)

74. Dipicolinic Acid

75. Spores Survival, not multiplication Resistant to heat, UV, chemicals, desiccation Bacillus spp. - aerobic Clostridium spp. - anaerobic

76. Bacillus anthracis Clostridium botulinum Clostridium tetani

77. VI. Microbial Locomotion 2.17 Flagella and Swimming Motility 2.18 Gliding Motility 2.19 Chemotaxis and Other Taxes

78. 2.17 Flagella and Swimming Motility Flagella: structure that assists in swimming –Different arrangements: peritrichous, polar, lophotrichous (Figure 2.48) –Helical in shape

79. Figure 2.48

80. 2.17 Flagella and Swimming Motility Flagellar structure of Bacteria –Consists of several components (Figure 2.51) –Filament composed of flagellin –Move by rotation Flagellar structure of Archaea –Half the diameter of bacterial flagella –Composed of several different proteins –Move by rotation

81. Figure 2.51 15–20 nm Filament Flagellin L P MS Hook Outer membrane (LPS) L Ring P Ring Rod Peptidoglycan Periplasm MS Ring Basal body C Ring Cytoplasmic membrane Fli proteins (motor switch) Mot protein 45 nm Rod MS Ring C Ring Mot protein ++++++++ −−−−−−−−

82. 2.17 Flagella and Swimming Motility Flagellar synthesis –Several genes are required for flagellar synthesis and motility (Figure 2.53) –MS ring is made first –Other proteins and hook are made next –Filament grows from tip

84. 2.17 Flagella and Swimming Motility Flagella increase or decrease rotational speed in relation to strength of the proton motive force Differences in swimming motions (Figure 2.54) –Peritrichously flagellated cells move slowly in a straight line –Polarly flagellated cells move more rapidly and typically spin around

85. Figure 2.54 Bundled flagella (CCW rotation) Tumble − flagella pushed apart (CW rotation) Flagella bundled (CCW rotation) CCW rotation Unidirectional flagella Reversible flagella CW rotation Cell stops, reorients CW rotation Peritrichous Polar

86. 2.18 Gliding Motility Gliding motility –Flagella-independent motility (Figure 2.56) –Slower and smoother than swimming –Movement typically occurs along long axis of cell –Requires surface contact –Mechanisms Excretion of polysaccharide slime Type IV pili Gliding-specific proteins

87. Figure 2.56 Cytoplasmic membrane Peptidoglycan Outer membrane Glide proteins Movement of outer membrane glide proteins In Out Surface Movement of cell

88. 2.19 Chemotaxis and Other Taxes Taxis: directed movement in response to chemical or physical gradients –Chemotaxis: response to chemicals –Phototaxis: response to light –Aerotaxis: response to oxygen –Osmotaxis: response to ionic strength –Hydrotaxis: response to water

89. 2.19 Chemotaxis and Other Taxes Chemotaxis –Best studied in E. coli –Bacteria respond to temporal, not spatial, difference in chemical concentration –“Run and tumble” behavior (Figure 2.57) –Attractants and receptors sensed by chemoreceptors

90. Figure 2.57 Tumble Run Attractant No attractant present: Random movement Attractant present: Directed movement Tumble

91. VII. Eukaryotic Microbial Cells 2.20 The Nucleus and Cell Division 2.21 Mitochondria, Hydrogenosomes, and Chloroplast 2.22 Other Major Eukaryotic Cell Structures

92. 2.20 The Nucleus and Cell Division Eukaryotes –Contain a membrane-enclosed nucleus and other organelles (e.g., mitochondria, Golgi complex, endoplasmic reticula, microtubules, and microfilaments (Figure 2.60)

93. Figure 2.60 Smooth endoplasmic reticulum Rough endoplasmic reticulum Cytoplasmic membrane Mitochondrion Microfilaments Lysosome Chloroplast Nuclear envelope Nuclear pores Nucleolus Nucleus Golgi complex Ribosomes Flagellum MitochondrionMicrotubules

94. 2.20 The Nucleus and Cell Division Nucleus: contains the chromosomes (Figure 2.61) –DNA is wound around histones (Figure 2.61b) –Visible under light microscope without staining –Enclosed by two membranes –Within the nucleus is the nucleolus Site of ribosomal RNA synthesis

95. Figure 2.61 Nucleus Nuclear pores Vacuole Lipid vacuole Mitochondria Double-stranded DNA Nucleosome core Histone H1 Core histones

96. 2.20 The Nucleus and Cell Division Cell division –Mitosis Normal form of nuclear division in eukaryotic cells Chromosomes are replicated and partitioned into two nuclei (Figure 2.62) Results in two diploid daughter cells –Meiosis Specialized form of nuclear division Halves the diploid number to the haploid number Results in four haploid gametes

97. Figure 2.62

98. . 21 Mitochondria, Hydrogeno2somes, and Chloroplast All specialize in energy metabolism –Mitochondria (Figure 2.63) Respiration and oxidative phosphorylation Bacterial dimensions (rod or spherical) Over 1,000 per animal cell Surrounded by two membranes Folded internal membranes called cristae –Contain enzymes needed for respiration and ATP production Innermost area of mitochondrion called matrix –Contains enzymes for the oxidation of organic compounds

100. Ribosomes

102. Structure double stranded DNA Each Strand is monomers connected by condensation RX sugar of one connected to the Phosphate of the other Covalent phosphodiester bond Two stands are anti-parallel held together H-bonds complementary base pairs (bp) A= TG=C molecule twisted to form helix Central Dogma of Cell Biology* DNA  RNA  Protein

103. Nucleic acids Nucleic acids are composed of nucleotides can occur as monomers or polymers Components of nucleotide: 1.Sugar 2.Nitrogen containing base 3.Phosphate group Structural differences between DNA and RNA 1.Different sugars: deoxyribose & ribose 2.Different N-bases: A,C,G,T vs A,C,G,U 3.DS vs SS

104. Plasmids Not Essential to growth Genes that enhance the survivability Antibiotic resistance Sex pili Conjugation F+