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.

This quiz explores the fundamental concepts of microorganisms and the historical perspectives on disease management in early civilizations. Learn about the advancements made by influential figures such as Hippocrates and Thucydides in understanding disease causation. Test your knowledge on how early societies managed health and sanitation.