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Bacteria and viruses


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Bacteria and viruses

  1. 1. Bacteria and VirusesKatie Burke & Aliya Alidina
  2. 2. Contents• What is bacteria?• What are the components of bacteria? – Cell wall – Capsule – Cell surface membrane – Flagellum – Pilus – Mesosome – DNA and Plasmids• What is a virus?• The life cycle• Similarities and differences
  3. 3. Back to Contents What is Bacteria?• They are prokaryotic organisms• Many are pathogens• But many are beneficial to organisms – In the human gut – The carbon cycle – The nitrogen cycle
  4. 4. Cell wall Gram-Positive Gram-Negative • The cell wall has a thick layer • The cell wall has a thin layer of of peptidoglycan peptidioglycan • This layer has teichoic acid • There is no teichoic acid • The cell wall also contains • There is an outer and inner surface proteins and a plasma membrane with inner and outer membrane membrane proteins • The crystal violet bind to the • There are lipopolysaccharides teichoic acid to give it the • The cells appear red in crystal purple/blue colour violetBack to Contents
  5. 5. Back to Contents Capsule• Otherwise known as a slime layer if it is very thin• This is around the cell wall• It protects the bacteria from phagocytosis by white blood cells• However it also helps the bacteria stay hydrated
  6. 6. Back to Contents Cell Surface Membrane• This is similar in the structure and function to that of a eukaryotic cell
  7. 7. Back to Contents Flagellum• This provides the bacteria with movement• It does this due to rapid rotations
  8. 8. Back to Contents Pilus• These are protein projections from the surface of bacteria• They attach to the host cell but also to each other• It can be used for sexual reproduction• But it can cause an entry point for bacteriophages
  9. 9. Back to Contents Mesosome• This is an infolding part of cell membrane• This is thought to be the site of respiration• However there is still some debate of their full function
  10. 10. Back to Contents DNA and Plasmids• DNA comes in the form of a single circular piece• Smaller pieces are known as plasmids• DNA is free in the cytoplasm
  11. 11. Back to Contents What is a Virus• There is much debate over this• Overall it is a micro- organism• They only contain nucleic acid and a protein coat although some have an envelope
  12. 12. Back to Contents The Life CycleLysogenic Pathway Lytic Pathway
  13. 13. Back to ContentsOrganelles of Bacterium vs. VirusesBacterium Viruses• Cell wall • Nucleic Acid (possibly• Capsule DNA)• Cell surface membrane • A protein coat or capsid• Ribosomes• Flagellum • Some have an envelope• Pilus• Mesosome• DNA and Plasmids