Biol2333-Chp1-Dr.Raj-Fa2022

Chapter 1

The Microbial World and You

Microbes and Microorganisms

  • Definition: Microbes are living organisms only visible under a microscope.

  • Size Range: Microbial cells range from millimeters (mm) to 0.2 micrometers (µm); viruses may be even smaller.

  • Cell Structure: Many microbes are unicellular and possess the genetic capacity to reproduce.

Microbiology

  • Field of Study: Microbiology is the study of organisms too small to be seen without magnification, employing tools like microscopes to observe them.

Types of Microorganisms

  • Categories:

    • Bacteria

    • Protozoa

    • Fungi

    • Helminths

    • Algae

    • Viruses

  • Microbial sizes depicted using different microscopy techniques: SEM (Scanning Electron Microscopy) and LM (Light Microscopy).

Microbial Communities

  • Example: Biofilms.

  • Viruses: Mimivirus as an example that challenges traditional definitions of microbes.

Importance of Microbes

  • Roles:

    • Pathogenic microbes cause diseases.

    • Decomposition of organic waste and generation of oxygen via photosynthesis.

    • Production of chemical products such as ethanol, acetone, and vitamins.

    • Fermentation of foods like vinegar and cheese.

    • Manufacturing products such as cellulase and insulin.

Three Domains of Life

  • Domains:

    • Bacteria (Prokaryotes)

    • Archaea (Prokaryotes)

    • Eukarya (Eukaryotes, including plants and fungi)

Origins of Microorganisms

  • Bacteria-like organisms have existed for approximately 3.5 billion years. Two types:

    • Prokaryotes: Simple cells with no nucleus.

    • Eukaryotes: Complex cells with a nucleus.

Microbial Structure

  • Viruses: Acellular and parasitic, composed of nucleic acid and protein.

  • Prokaryotes: Unicellular organisms lacking nuclei and membrane-bound organelles.

  • Eukaryotes: Unicellular or multicellular organisms possessing a nucleus and membrane-bound organelles.

Microbes in Ecosystems

  • Energy and Nutrient Flow:

    • Photosynthesis converts CO2 to organic materials.

    • Decomposition breaks down dead matter into simpler compounds.

Microbial Lifestyles

  • Most microorganisms have harmless or beneficial roles. However, some can be parasites, damaging their host.

Human Use of Microorganisms

  • Biotechnology and Genetic Engineering: Production of foods, drugs, and vaccines.

  • Bioremediation: Using microbes to solve environmental problems.

Historical Impact of Microbes

  • Microbes influenced food and beverage production and mining. They have shaped human culture since ancient civilizations.

  • Examples of diseases affecting demographics:

    • Bubonic plague (Yersinia pestis)

    • Tuberculosis (Mycobacterium tuberculosis)

    • HIV/AIDS

    • Covid-19 (SARS-CoV-2)

Microbes in Wars

  • More soldiers died from infections than wounds. Noted by Florence Nightingale as early recognition of the importance of microbial disease.

Pathogens and Infectious Diseases

  • Pathogens are microbes causing harm. Approximately 2,000 different microbes are responsible for diseases, with billions of infections and millions of deaths annually.

Causes of Death Worldwide

  • Statistics on leading causes of death vary by country income level, indicating the significant impact of infectious diseases.

Foundations of Microbiology

  • Significant discoveries in microbiology over 300 years include microscopy and the germ theory of disease.

Key Figures in Microbiology

  • Robert Hooke: First compound microscope; coined "cell."

  • Antonie van Leeuwenhoek: First to observe living microbes, termed them "animalcules."

Spontaneous Generation vs. Biogenesis

  • Spontaneous Generation: Belief that life could arise from nonliving matter. Disproved by Pasteur in the theory of biogenesis.

Scientific Method in Microbiology

  1. Observation of phenomena.

  2. Hypothesis formation.

  3. Experimental testing.

  4. Publication of results for verification.

Discovery of Spores and Sterilization

  • Tyndall and Cohn demonstrated heat-resistant microbes; sterilization defined as elimination of all life forms.

Aseptic Techniques

  • Techniques developed by Holmes and Lister to reduce infections in medical settings.

Germ Theory of Disease

  • Numerous diseases caused by microbial growth; largely established by Pasteur and Koch.

Immunization and Vaccination

  • Edward Jenner pioneered vaccination via cowpox inoculation, leading to smallpox eradication.

Taxonomy Basics

  • Taxonomy: Classification and naming of organisms.

  • System developed by Carl von Linné.

Levels of Taxonomy

  • Domains, Kingdoms, Phyla, Classes, Orders, Families, Genus, Species.

Binomial Nomenclature

  • Two-part naming system for organisms: Genus (capitalized) and species (lowercase).

Evolution and Phylogeny of Microorganisms

  • Evolution from preexisting species; complexity increases over time.

Five Kingdom Classification System

  • Whittaker’s Classification based on cell structure and nutritional type:

    • Bacteria, Archaea, Eukarya.

Characteristics of Microorganisms

  • Bacteria: Prokaryotic, single-celled, with peptidoglycan walls.

  • Fungi: Eukaryotic, absorb nutrients, can be unicellular or multicellular.

  • Protozoa: Eukaryotic, motile, can be free-living or parasitic.

  • Algae: Eukaryotic, perform photosynthesis, found in various ecosystems.

  • Viruses: Acellular, reliant on host cells for replication.

Chemotherapy and Antibiotics

  • Chemotherapy involves chemical treatment of diseases using synthetic drugs or antibiotics produced by microorganisms.

Milestones in Microbiology

  • Overview of key discoveries and contributions by Pasteur, Koch, and others that shaped the understanding of microbes and their applications in disease treatment.