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Humans and the Microbial World Chapter 1 Kathleen’s Professional Fit 2406 17th Greeley 356-7209 20% Discount on lab coats and safety glasses (must present student ID) Current Microbial Threats Measles (vaccine preventable) Polio (vaccine preventable)

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Humans and the Microbial World

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Kathleen’s Professional Fit

2406 17th



20% Discount on lab coats and safety glasses

(must present student ID)

current microbial threats
Current Microbial Threats
  • Measles (vaccine preventable)
  • Polio (vaccine preventable)
  • Whooping cough (pertussis; vaccine preventable)
  • Severe acute respiratory syndrome (SARS CoV)
  • Malaria
  • Yellow fever virus
  • West nile virus
  • Tuberculosis
  • Human immunodeficiency virus (HIV; AIDS)
  • Hepatitis C virus
  • Multidrug-resistant Staphylococcus aureus
  • H5N1 Avian Influenza
  • Hospitals
1 1 the world of microorganisms
1.1 The World of Microorganisms
  • Spontaneous Generation: Life from nonliving materials
    • Disproved by Francesco Redi in late 1600s
      • Showed that worms which appeared on rotting meat were from fly eggs
    • Disproved again by Louis Pasteur in mid 1800s
      • Showed that appearance of microbes in sterilized media was from air-borne bacteria
      • Showed that sterilized materials remained sterile if kept isolated from the external environment
1 2 microbiology a human perspective
1.2 Microbiology: A Human Perspective
  • Microorganisms cannot be seen without the aid of a microscope
  • There are more than 200,000 known microbes
  • Exist in virtually any environment that has water
  • Exhibit tremendous biodiversity
  • Compose the largest biomass group of living organisms

Vital activities of microorganisms

  • Nitrogen fixation: Converting atmospheric nitrogen (gas) to biomolecules (e.g., nucleic acids, amino acids)
  • Oxygen production: Convert carbon dioxide to molecular oxygen (O2)
  • Degradation of organic materials
    • Gastrointestinal tract
    • Sewage treatment plants

Applications of Microbiology

  • Food production: bread, beer
  • Bioremediation: decontamination of hazardous wastes
  • Useful products: ethanol fuel, antibiotics, amino acids
  • Genetic engineering: pharmaceuticals, vaccines
  • Genomics: genome sequencing permits understanding of disease mechanisms

Medical microbiology

  • Infectious diseases have killed more people than all wars and natural disasters combined
  • Outbreaks have changed the course of history
  • Notable pandemics
    • Spanish Flu (1918-1919): 50 million global deaths
    • Smallpox (middle ages): >100 millions deaths (est.)
    • Plague (1300s-1800s): >100 million deaths (est.)
    • Introduction of European diseases killed 30 to 40 million Native Americans (est.)
  • Vaccines have dramatically decreased the incidence of infectious diseases, especially in children

Medical microbiology (cont.)

  • Re-emergence of “Old” Infectious Diseases
    • Colorado has one of the lowest childhood vaccination rates in the U. S.
    • Cases of whooping cough have increased in the last few years
    • Many microbes have evolved antibiotic resistance

Medical microbiology (cont.)

  • Emerging infectious diseases
    • As humans encroach upon wild habitat, new infectious agents (microbes) are discovered
    • These agents are typically hosted by animals and are termed zoonotic agents

Some recently discovered agents and their animal hosts

1 3 the microbial world
1.3 The Microbial World
  • Bacteria
    • Procaryotes (no organelles)
    • Most have rigid cell walls composed of peptidoglycan
  • Archaea
    • Similar to bacteria, but no peptidoglycan
    • Often found in extreme environments (temperature, pH, high salt, etc.)
    • Complex organelles
    • Larger than bacteria and archaea
    • Members
      • Algae (photosynthesis)
      • Fungi (single and multicelluar)
      • Protozoa
  • Nomenclature
    • Genus is capitalized
    • Species is not
    • Both are italicized
    • Example: Yersina pestis
1 4 viruses viroids and prions
1.4 Viruses, Viroids, and Prions
  • Viruses
    • Not considered living; they are complex macromolecules composed of nucleic acids and proteins (some have lipids)
      • Noninfectious viruses are said to be inactivated; you cannot “kill” a virus (since they are not considered living organisms)
    • Obligate intracellular parasites
    • Tend to be species-specific
    • Reside in a reservoir host in which they cause limited pathology or are chronic
      • Disease usually occurs when the virus “jumps” species
      • Deer mice permanently host Sin Nombre hantavirus without pathology (disease)
      • Humans infected with SNV often develop hantavirus cardiopulmonary syndrome
    • Composed of RNA
    • Smaller than viruses
    • Rely on other viruses to replicate
    • Best characterized in plants
  • Prions
    • Composed of proteins only
    • Cause neurological disease, termed spongiform encephalopathy
    • Can be transmitted to humans from some animals (e.g. “mad cow”)