Bacteria Viruses09martin
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Bacteria Viruses09martin



Overview of microorganisms (bacteria and viruses)

Overview of microorganisms (bacteria and viruses)



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Bacteria Viruses09martin Bacteria Viruses09martin Presentation Transcript

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