Biology 260: Review for Final

1. Biology 260: Review for Final

2. Microorganisms • Bacteria: unicellular prokaryotic organisms; extremely diverse, adapted to essentially all habitats • Fungi: unicellular or multicellular eukaryotic organisms • Protozoa: unicellular eukaryotic organisms • Algae: unicellular or multicellular eukaryotic organisms

3. Viruses • Protein coat = capsid + nucleic acid • DNA (ds or ss) or RNA (ss) • Not living organisms • Not a true cell • No cell membrane • Enveloped viruses have a “stolen membrane” that they acquire when budding out of an infected cell • No nucleus

6. Bacterial Structures

7. Cell Wall Gram-positive Thick layer of peptidoglycan Teichoic acids

8. Cell WallGram-negative • Thin layer of peptidoglycan • Outer membrane - additional membrane barrier • Lipopolysaccharide(LPS) O antigen Core polysaccharide Lipid A

9. Cytoplasmic membrane • Defines the boundary of the cell • Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules • Transport proteins function as selective gates (selectively permeable) • Control entrance/expulsion of antimicrobial drugs • Receptors provide a sensor system • Phospholipid bilayer, embedded with proteins • Fluid mosaic model

10. Cytoplasmic membrane Electron transport chain Electron transport chain - Series of proteins that eject protons from the cell, creating an electrochemical gradient • Proton motive force is used to fuel: • Synthesis of ATP (the cell’s energy currency) • Rotation of flagella (motility) • One form of active transport across the membrane

11. Internal structures: Ribosomes

12. Unique molecules in bacteria can be used as targets for chemotherapy • Cell wall: peptidoglycan, techoic acid • Ribosomes • Unique biosynthetic pathways

14. Bacterial growth & metabolism • Binary fission • Growth = increase in # • Generation time: time it takes to double the population • Pathogens with a short generation time cause rapidly progressive disease (i.e. Vibrio cholera) • Pathogens with a long generation time cause chronic, slowly progressive disease (i.e. Mycobacterium tuberculosis)

15. Growth = increase in # • Many of our drugs are most effective against growing bacteria – • Interrupt cell wall synthesis • Interrupt/block replication • Interrupt/block translation • Interfere with biosynthetic pathways

16. Primary and Secondary metabolites

17. Requirements for bacterial growth • Environmental factors that influence • Temperature, pH, osmotic pressure, oxygen • Nutritional factors • Carbon, nitrogen, sulfur, and phosphorous • Trace elements: iron

18. Chemical control: choosing the right germicidal chemical • What is your goal? • What type or organism are you targeting? • What environment are you treating? • sterility vs. disinfection; level of disinfection required dictates potency of chemical required • Toxicity: risk-benefit analysis • Activity in presence of organic material: most are diminished or inactivated • Sensitivity of the material to be treated • Residue: toxic or corrosive vs residual desired antimicrobial effect • Cost and availability • Storage and stability: concentrate vs stock solution • Environmental risk: antimicrobials in the environment

19. Innate immune system • 1st line defenses: skin, mucosal barriers, secretions - antimicrobials (lysozyme), iron-binding proteins (transferrin) • Complement system • Granulocytes (neutrophils, eosinophils, mast cells), monocytes/macrophages, dendritic cells

20. Antimicrobial substances • Produced by animals: • Lysozyme • Peroxidase enzymes • Lactoferrin • Transferrin • Defensins • Produced by your microbiota: • Fatty acids • Colicins • Lactic acid

21. Immune Defenses • Sensory systems: • Pattern recognition receptors • Toll-like receptors • NOD-like receptors • RIG-like receptors • Complement system • Alternative pathway • Classical pathway • Lectin pathway

22. The Complement System • Central feature = splitting of C3 → C3a & C3b • Enzyme that splits C3 = C3 convertase • C3 also spontaneously degenerates to form C3a & C3b at a constant rate • Alternative pathway: C3b binds to foreign cell surface receptors → formation of C3 convertase • Lectin pathway: pattern recognition receptors = mannose binding lectins (MBLs): bind to mannose molecules on microbial surface → formation of C3 convertase • Classical pathway: antibody binds antigen = antigen-antibody complex → formation of C3 convertase (adaptive immune response)

24. Leukocytes • Phagocytes: macrophages & neutrophils • Antigen presenting cells • Natural killer cells

25. The Acute Inflammatory Response • Calor = heat: increased blood flow to site • Rumor = redness: increased blood flow • Tumor = swelling: fluid and cells accumulate • Dolor = pain: pressure + chemical mediators • Functiolaesa = loss of function: many possible causes . . .

26. The acute inflammatory response

27. Leukocytes have to get out of the blood vessels: recruitment

28. The Adaptive Immune Response • Primary response • Secondary response • Humoral immunity: • B cells, plasma cells, antibodies: target extracellular pathogens • Cell-mediated immunity • T cells, dendritic cells – antigen is inside a cell

29. Overview of the Adaptive Immune Response

30. Lymphocytes • CD4 = T helper lymphocytes • Activate B cells, macrophages and cytotoxic T cells • Memory T cells • CD8 = Cytotoxic T lymphocytes • B cells • Naïve • Activated • Mature = plasma cell (no longer a dividing cell) • Memory B cells

31. How are B cells activated?

32. What can happen when antibody binds antigen?

33. MHC • MHC class II molecules • Expressed by antigen-presenting cells • Used to present exogenous (non-self) antigen • MHC class I molecules • Expressed on the surface of all cells • Used to present endogenous (self) antigen • Allows recognition and elimination of infected cells – viruses, intracellular bacteria

34. Helper T cells recognize MHC Class II

35. Cytotoxic T cells recognize MHC Class I markers

37. What determines outcome of infection? • Host defenses: functional immune system? Age? • Predisposing infection or other disease? Injury? • Pathogenicity of organism – virulence factors; evasion or invasion tactics? • Infectious dose – very large numbers of an organism that is not very virulent will still be able to establish infection; some organisms are so virulent that only a few organisms are required to establish an infection

38. Colonization • 2 possible outcomes: • Symbiosis • Infection • Infection: • Subclinical vs infectious disease • Primary vs secondary infection • Opportunist vs primary pathogen

39. Establishing infection • Adherence • Pili, capsules, cell wall components – binding to receptors on host cells • Colonization • Compete for iron, nutrients • Resist opsonization • Resist resident’s antimicrobials • Secretion systems

40. Exploitation of antigen sampling processes

41. Avoiding host defenses • Hide in cells • Avoid complement-mediated killing • Avoid phagocytosis • Survive in phagocytes • Avoid antibodies

42. Disease: damage to host • Damage caused by bacterial exotoxins • Proteins synthesized by bacteria • Highly specific interactions with host cells • Highly immunogenic • Toxoids • Antitoxin

43. Diseases caused by exotoxins • Neurotoxins • Botulism • Tetanus • Entereotoxins • Cholera • Traveler’s diarrhea • Cytotoxins • Anthrax • Pertussus (whooping cough) • Diptheria • Hemolytic uremic syndrome • Dystentery • Membrane-damaging toxins: • Gas gangrene • Strep throat • Abscesses • Superantigens • Some foodborne intoxications • Toxic shock syndromes

44. Cholera Etiologic agent: Vibriocholerae Toxin: cholera toxin Toxin type: A-B toxin Cell type with receptor: human enterocytes

45. Mechanisms of antimicrobial drugs • Inhibition of cell wall synthesis • Inhibition of protein synthesis • Inhibition of nucleic acid synthesis • Inhibition of biosynthetic pathways • Disruption of cell membrane integrity

46. Mechanisms of acquired drug resistance • Destruction or inactivation of the drug: drug inactivation enzymes • Alteration of target molecule (mutation) • Decreased uptake: alteration of porins • Increased elimination: efflux pumps

47. Acquiring resistance • Spontaneous mutation • Gene transfer • R plasmids

48. Genetics review Replication: duplication of the genome prior to cell division Gene expression: decoding of DNA in order to synthesize gene products (proteins): Transcription: DNA →RNA Translation: RNA → protein

49. Enzymes necessary for DNA replication • Primase: synthesizes the RNA primer • DNA Polymerase: synthesize 5’→3’ • DNA gyrase: releases tension during uncoiling of circular DNA **target of quinolones and aminocoumarins** • DNA ligase: seals the gaps between Okazaki fragments (forms covalent bonds) • Helicase: “unzips” 2 strands of DNA

50. ESBL producers are resistant to all β-lactam drugs: • Penicillins • Cephalosporins • Carbapenems • Vancomycin • Bacitracin