Microorganisms and Early Diseases - Chapter 1.1

Microorganisms and Disease

• Microorganisms are organisms too small to be seen with the naked eye.
• Early civilizations correlated sewage with disease, constructing aqueducts to transport waste away efficiently.

Contributions to Disease Understanding

• Hippocrates: Recognized natural causes of diseases, rejected supernatural explanations.
• Thucydides: Emphasized evidence-based analysis, establishing a cause-and-effect framework.
• Marcus Terentius Varro: Proposed invisible entities (microorganisms) could lead to disease.

Contributions to Microscopy

• Zacharias Janssen: Invented the first simple microscope, laying groundwork for future developments.
• Robert Hooke: Enhanced microscope with fine adjustments and better lighting for improved observation.
• Antony van Leeuwenhoek: Known as the "Father of Microbiology" for first observing microbes via a developed lens.

Golden Age of Microbiology

• Louis Pasteur: Established germ theory, disproving spontaneous generation and creating the rabies vaccine.
• Robert Koch: Identified specific pathogens causing diseases like cholera and anthrax.
• Attenuation principle reduced pathogen danger for vaccine development.

Taxonomy and Classification

• Taxonomy: The classification system for living organisms to categorize species.
• Carolus Linnaeus: Developed binomial nomenclature, systematizing species naming.
• Ernst Haeckel: Introduced a fourth kingdom, including protista and monera.
• Robert Whitaker: Proposed a five-kingdom system, adding fungi.
• Carl Woese: Classified life into three domains: bacteria, archaea, and eukarya.
• Current kingdoms: Animalia, Plantae, Fungi, Protista, Archaea, Bacteria.
• Current domains: Bacteria, Archaea, Eukarya.
• Eight taxonomic ranks: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
• Organism naming: Italicized names with only the genus capitalized.
• Bergey’s Manual: A resource for classifying and identifying prokaryotes.

Microbial Measurement

• Metric equivalents: 1 decimeter = 0.1 m; 1 centimeter = 0.01 m; 1 millimeter = 0.001 m; 1 micrometer = 1e-6 m; 1 nanometer = 1e-9 m.
• Human eye's limitation is detecting objects smaller than 1 mm (100 micrometers).
• Average sizes: Animal cell = 10 micrometers; bacterial cell = 1 micrometer; virus = 0.1 micrometer.

Bacteria and Their Characteristics

• Bacterial cells consist of a cell wall, plasma membrane, cytoplasm, ribosomes, and DNA.
• Common bacteria shapes: Bacilli (rod-shaped), Cocci (spherical), Spirillum, Spirochete, Vibrio (spiral).
• Archaea: Thrive in extreme environments (high/low temperatures, acid/alkaline conditions).
• Algae uses: Biofuels, food sources, pharmaceutical products, and oxygen production.
• Protozoa classification based on movement mechanisms: Cilia, flagella, pseudopods.

Fungi Characteristics

• Fungi can be unicellular (yeast) or multicellular (mold), functioning as decomposers.
• Yeast: Unicellular, utilized in food products, some cause diseases.
• Mold: Multicellular, used in pharmaceuticals, may prompt allergies.
• Helminths: Multicellular parasitic worms that spread through microscopic eggs and larvae.

Viruses

• Composed of DNA or RNA; not consider alive due to lack of reproduction and metabolism.

Subfields of Microbiology

• Bacteriology: Study of bacteria.
• Mycology: Study of fungi.
• Protozoology: Study of protozoa.
• Parasitology: Study of helminths and parasites.
• Virology: Study of viruses.
• Immunology: Study of the immune system.

Historical Perspectives on Microbial Life

• Abiogenesis: The theory that life arises from non-living matter.
• Francisco Redi's experiment: Showed that decaying meat does not generate flies but is affected by them.
• Louis Pasteur's experiment: Demonstrated that microorganisms do not grow in sterile broth unless exposed to air.

Cell Theory and Germ Theory

• Cell theory states that all cells arise from pre-existing cells.
• Robert Hooke discovered cells in cork under a microscope.
• Germ theory posits that many diseases result from microbial infections.

Contributions to Public Health

• Ignaz Semmelweis: Found that handwashing reduced mortality in childbirth.
• John Snow: Mapped cholera cases, identifying a contaminated water source.
• Joseph Lister: Advocated using carbolic acid to prevent postoperative infections.
• Florence Nightingale: Employed statistics to highlight preventable causes of death linked to sanitation and hygiene.

Koch's Postulates

• Microbe must be present in all sick cases.
• Microbe must be cultured outside the body.
• Microbe must cause disease in a healthy species.
• Microbe must be isolated from the experimental host.

Exceptions to Koch's Postulates

• Some microbes cannot be isolated outside the body.
• Certain pathogens can cause multiple diseases.
• Some diseases occur in specific hosts only.

Modern Focus of Germ Theory

• Investigates antibiotic resistance.
• Explores new diseases and those involving multiple organisms.
• Examines mechanisms of microbial agents in disease.