Bacteria Viruses09martin


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Overview of microorganisms (bacteria and viruses)

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Bacteria Viruses09martin

  1. 1. Viruses and Bacteria
  2. 2. Viruses <ul><li>Living or Non-Living? </li></ul><ul><li>Infectious particles of nucleic acid and proteins </li></ul><ul><li>Cannot “live” (reproduce) outside a host </li></ul>
  3. 3. History/Discovery <ul><li>1883 Adolf Mayer sought cause of Tobacco Mosaic Disease </li></ul><ul><li>1935- Wendell Stanley crystallized the infectious particle—determined it was NONLIVING (can’t crystallize cells) </li></ul>
  4. 4. <ul><li>1 st virus discovered-Tobacco Mosaic Virus (TMV) </li></ul>
  5. 5. Virus Structure <ul><li>Very small and simple (smaller than a ribosome ~20nm in diameter) </li></ul><ul><li>Made of DNA or RNA surrounded by a protein coat (capsid) </li></ul>
  6. 6. Characteristics <ul><li>Host specific—identify host cells by “lock and key” fit between proteins on virus and host cell receptors </li></ul><ul><li>*Presumed that receptors first evolved because they carried out some functions that benefited the organism </li></ul>
  7. 8. Naming Viruses <ul><li>International Committee on Taxonomy of Viruses names them based on three characteristics: </li></ul><ul><ul><li>Type of nucleic acid (DNA or RNA) </li></ul></ul><ul><ul><li>Is the nucleic acid double or single stranded </li></ul></ul><ul><ul><li>Presence or absence of nuclear envelope </li></ul></ul>
  8. 9. Viral Infection <ul><li>Lytic Infection- virus enters the cell, makes copies of itself, and causes the cell to burst </li></ul><ul><li>Lysogenic Infection- virus integrates it DNA into the DNA of the host. Viral DNA replicates with host DNA </li></ul>
  9. 10. Viral Reproduction <ul><li>Steps of Lytic Cycle </li></ul><ul><ul><li>Attachment </li></ul></ul><ul><ul><li>Entry </li></ul></ul><ul><ul><li>Replication </li></ul></ul><ul><ul><li>Assembly </li></ul></ul><ul><ul><li>Lysis/Release (lyses the cell) </li></ul></ul>
  10. 13. Retroviruses <ul><li>Contain RNA instead of DNA </li></ul><ul><li>Copy their RNA into DNA instead of DNA to RNA </li></ul><ul><li>Examples: AIDS, some cancers </li></ul>
  11. 14. Bacteria <ul><li>Most numerous and widespread organisms </li></ul><ul><li>“ Discovered” with the invention of the microscope by Robert Hooke and Anton van Leeuwenhoek (1676) </li></ul>
  12. 15. Classification <ul><li>Two kingdoms of Prokaryotes (Prokaryotes are organisms that lack nuclei or membrane-bound organelles) </li></ul><ul><li>Kingdom Eubacteria : “true bacteria” , variety, 3 shapes, no phyla </li></ul><ul><li>Kingdom Archaebacteria: “ancient”, lives in extreme environments </li></ul>
  13. 16. Archaebacteria <ul><li>Methanogens–live in large intestines of animals, decompose dead organisms, produce methane gas (CH 4 ) </li></ul><ul><li>Halophiles--live in salty environments </li></ul><ul><li>Thermoacidophiles—live in hot, acidic environments </li></ul>
  14. 17. Size and Structure <ul><li>1-5 micrometers (much smaller than eukaryotic cells– 10-100 micrometers) </li></ul><ul><li>Unicellular (although grow in colonies) </li></ul><ul><li>Prokaryotic- no nucleus, no membrane-bound organelles </li></ul><ul><li>* CAN IDENTIFY BACTERIA BASED ON: </li></ul><ul><ul><li>Shape, Cell Wall, and Movement </li></ul></ul>
  15. 18. Method of Obtaining Energy <ul><li>Most are heterotrophic (mostly decomposers) </li></ul><ul><li>Some are autotrophic—chemotrophs and photoautotrophs </li></ul><ul><ul><li>Ex: cyanobacteria </li></ul></ul>
  16. 19. Shape <ul><li>Coccus (spherical)* </li></ul><ul><li>Bacillus (rod-shaped)* </li></ul><ul><li>Spirillum (spiral-shaped)* </li></ul><ul><li>*Arranged in chains, groups, or pairs </li></ul><ul><ul><li>Pair– Diplo- </li></ul></ul><ul><ul><li>Chains– Strepto- </li></ul></ul><ul><ul><li>Groups– Staphylo— </li></ul></ul><ul><ul><li>**Example: Spherical shaped bacteria arranged in chains would be named, “Streptococcus” </li></ul></ul>
  17. 22. Cell Wall <ul><li>For Eubacteria only! </li></ul><ul><ul><li>Gram negative- thin cell wall consisting of a few layers of peptidoglycan </li></ul></ul><ul><ul><li>Gram positive- thick cell wall consisting of many layers of peptidoglycan </li></ul></ul>
  18. 23. Typical Bacterial Cell <ul><li>Cell wall </li></ul><ul><li>Cell membranes </li></ul><ul><li>DNA (floating freely)-circular chromosome </li></ul><ul><li>Ribosomes </li></ul><ul><li>Some can move (flagella, others glide) </li></ul>
  19. 25. Reproduction <ul><li>Most bacteria reproduce by Binary Fission </li></ul><ul><ul><li>Produces 2 identical “daughter” cells </li></ul></ul><ul><ul><li>Can grow and divide every 20 minutes </li></ul></ul><ul><ul><li>Asexual (no exchange or recombination of genetic information) </li></ul></ul>
  20. 26. Image of E. coli going through Binary fission
  21. 27. Ways bacteria can accomplish genetic recombination (variation) <ul><li>Conjugation - exchange of genes from 1 bacterial cell to another </li></ul><ul><li>Transformation -bacteria take up pieces of free DNA from another bacterial cell </li></ul><ul><li>Transduction - bacteriophage transfer portions of bacterial DNA from one cell to another . </li></ul>
  22. 28. E.coli undergoing conjugation
  23. 29. “ BAD” Bacteria <ul><li>Food Spoilage— smells, makes you sick </li></ul><ul><li>Bacterial Diseases </li></ul><ul><ul><li>Only 3% of all bacteria cause human diseases </li></ul></ul><ul><ul><li>Can be treated with antibiotics and prevented through vaccination </li></ul></ul><ul><ul><li>1 st antibiotic discovered/source </li></ul></ul><ul><ul><li>Examples: pneumonia, bubonic plague, Strep. Throat, Syphilis, gonorrhea, anthrax, botulism </li></ul></ul>
  24. 30. E. coli
  25. 31. “ GOOD” Bacteria: The Importance of Bacteria <ul><li>Decomposers </li></ul><ul><ul><li>Help ecosystem recycle nutrients </li></ul></ul><ul><ul><li>Breakdown complex compounds into usable materials </li></ul></ul><ul><li>Nitrogen fixers </li></ul><ul><ul><li>Bacteria perform nitrogen fixation </li></ul></ul>
  26. 32. Importance of Bacteria (Cont.) <ul><li>Human Uses </li></ul><ul><ul><li>Production of food and beverages </li></ul></ul><ul><ul><li>Medicine and chemical industry </li></ul></ul><ul><ul><li>Genetic engineering </li></ul></ul><ul><ul><li>Bioremediation: Cleaning up the environment </li></ul></ul>