BIOL 2460 Chapter 1

Microbiology Overview

  • Definition: Study of small organisms, often invisible to the naked eye (some exceptions).

  • Ubiquitous Nature: Microorganisms are found everywhere in the environment.

  • Categories: Microbes can be classified as beneficial, harmful, or neutral.

Historical Perspectives on Disease

Ancestors' Understanding

  • Pre-1800s Knowledge: Limited understanding of diseases; prevailing belief was the Miasma theory.

    • Quarantine Practices: References to leprosy in the Bible highlight early methods of disease control.

    • Roman Sanitation: Construction of sewer systems to manage waste shows early public health efforts.

Key Historical Figures

  • Hippocrates (460-370 BC)

    • Philosophy: Proposed that diseases have natural causes, not supernatural influences.

    • Contributions: Authored the Hippocratic Corpus and the Hippocratic Oath.

  • Thucydides (460-395 BC)

    • Influence: Recognized as the father of scientific history; documented events during the Athenian plague and introduced early concepts of immunity.

  • Marcus Terentius Varro (116-27 BC)

    • Theory: Suggested that invisible organisms could cause disease, as documented in Res Rusticae, referring to 'animalia minuta.'

Birth of Microbiology

  • Invention of the Microscope: Unknown but significantly contributed to the study of microorganisms.

  • Antonie van Leeuwenhoek (1632-1723)

    • Discovery: First to observe 'animalcules' in rainwater using a microscope.

    • Title: Recognized as the "Father of Microbiology" due to his pioneering work in microscopy.

The Golden Age of Microbiology (1857-1914)

  • Key Figures:

    • Louis Pasteur (1822-1895)

      • Discoveries: Identified the role of microbes in fermentation and spoilage; developed pasteurization and created vaccines (e.g., rabies).

    • Robert Koch (1843-1910)

      • Contribution: Established methods to link specific pathogens to specific diseases (Koch’s postulates) such as anthrax, cholera, and tuberculosis.

Comparative Influence: Pasteur vs. Koch

Notable Historical Figures in Microbiology

  • Hippocrates

  • Thucydides

  • Marcus Terentius Varro

  • Antonie van Leeuwenhoek

  • Louis Pasteur

  • Robert Koch

Systematic Approaches to Microbiology

Taxonomy and Classification

  • Pioneers of Taxonomy:

    • Carolus Linnaeus (1707-1778)

    • Ernst Haeckel (1834-1919)

    • Robert Whittaker (1920-1980)

    • Carl Woese (1928-2012)

    • George Fox (1945-present)

Classification Methods

  • Historical Classification: Based on observable traits.

  • Molecular Techniques: Developed by Woese & Fox that utilize small subunit ribosomal RNA (rRNA) sequences, leading to the three domains of life: Bacteria, Archaea, Eukarya.

Microbial Classification Challenges

  • Microbes pose a unique challenge for taxonomy due to the often absence of macroscopic features.

  • Molecular methods provide insights but don't encapsulate the complete picture.

  • Strain Identification: Indicate special biochemical features; classification levels include kingdom, phylum, class, order, family, genus, species, and strain (e.g., E. coli O157:H7).

Naming Organisms

  • Binomial Nomenclature: Two-word naming system based on genus and species; names usually derived from Latin or Greek roots.

    • Formatting Rules: Italics, with the genus capitalized and the species lowercase.

    • Examples:

      • Homo sapiens (H. sapiens)

      • Escherichia coli (E. coli)

      • Haloquadratum walsbyi

Bergey’s Manual of Determinative Bacteriology

  • A guide used for identifying microbes through various non-visual characteristics.

Types of Microorganisms

Microbial Diversity

  • Microbes vary drastically in form and size, including viruses, bacteria, and eukaryotes.

  • Visual representation: Relative sizes range from nanometers (viruses) to millimeters (large bacteria).

Units of Measurement in Microbiology

Metric Unit

Meaning of Prefix

Metric Equivalent

meter (m)

—

1 m = 1000 mm

decimeter (dm)

1/10

1 dm = 0.1 m

centimeter (cm)

1/100

1 cm = 0.01 m

millimeter (mm)

1/1000

1 mm = 0.001 m

micrometer (µm)

1/1,000,000

1 µm = 0.000001 m

nanometer (nm)

1/1,000,000,000

1 nm = 0.000000001 m

Characteristics of Microbes

  • Colony Structure: Variation among microbial colonies.

  • Habitat: Microbes thrive in diverse environments.

  • Metabolism: Different metabolic processes among groups.

  • Cellular Structure: Unicellular vs. multicellular, cellular vs. acellular.

Cellular Microbes Classification

  • Prokaryotes: Bacteria, Archaea

  • Eukaryotes: Algae, Protozoa, Fungi, Helminths

  • Acellular Microbes: Viruses and Prions

Shapes of Bacteria

  • Common forms include:

    • Coccus: Spherical

    • Bacillus: Rod-shaped

    • Vibrio: Comma-shaped

    • Coccobacillus: Short rod

    • Spirillum: Spiral-shaped

    • Spirochete: Corkscrew-shaped

Features of Archaea

  • Exhibits distinct evolutionary lineages, genetics, and metabolic processes compared to bacteria.

  • Often found in extreme environments and characterized by pseudopeptidoglycan cell walls.

Protists: Algae and Protozoa

  • Algae: Photosynthetic organisms important in ecosystems, fundamentally eukaryotic.

  • Protozoa: Diverse group of single-celled organisms characterized by varied motility (e.g., via cilia, flagella, pseudopodia).

Fungi Characteristics

  • Can be unicellular (yeasts) or multicellular (molds).

  • Defined by their chitin cell walls.

  • Can have both beneficial and harmful effects.

Helminths Overview

  • Multicellular parasitic worms, with microscopic eggs and larvae forms.

Viruses and Prions

  • Viruses: Acellular and require a host for replication.

  • Prions: Proteins that cause diseases, also acellular.