Humans and the microbial world
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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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Kathleen’s Professional Fit

2406 17th



20% Discount on lab coats and safety glasses

(must present student ID)

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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

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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

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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

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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

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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

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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

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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

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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

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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.)

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  • Eucarya

    • 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

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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

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  • Viroids

    • 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”)