Chapter 1: Introduction to Microbiology
Microorganisms and the Human Microbiome
Microorganisms: Organisms too small to be seen with the unaided eye.
Human Body Composition: Adult humans consist of body cells and harbor bacterial cells.
Human Microbiome: Resident microbes that maintain health, prevent pathogenic growth, and train the immune system.
Relationships:
Commensalism: One organism benefits without harming the host.
Mutualism: Both host and microbe benefit.
Parasitism: Microbe causes disease.
Opportunistic Pathogens: Commensals that become pathogenic under specific conditions (e.g., immunocompromised host, altered niche).
Biodiversity & Homeostasis: Microbial diversity maintains ecosystem balance; loss of diversity is linked to chronic illnesses (e.g., diabetes, autoimmune diseases, Crohn's).
Roles and Applications of Microbes
Ecology: Maintain chemical balance, form aquatic food chains, decompose matter, fix nitrogen, and produce oxygen.
Bioremediation: Microbes degrade environmental pollutants (e.g., sewage treatment, oil spill cleanup).
Industry: Microbes are used to produce fermented foods, vitamins, drugs, and recombinant therapeutics like human insulin.0Scientific Nomenclature and Classification
Binomial Nomenclature: Two Latinized names written in italics or underlined—Genus (capitalized) and specific epithet (lowercase).
Three Domains:
Bacteria: Single-celled prokaryotes with peptidoglycan cell walls.
Archaea: Single-celled prokaryotes lacking peptidoglycan, often inhabiting extreme environments.
Eukarya: Complex organisms containing a membrane-bound nucleus and organelles.
Major Groups of Microorganisms
Fungi: Eukaryotes with chitin cell walls (multicellular molds/mushrooms, unicellular yeasts).
Algae: Photosynthetic eukaryotes with cellulose cell walls.
Protozoa: Unicellular, motile eukaryotes lacking cell walls.
Helminths: Multicellular parasitic flatworms and roundworms.
Viruses: Acellular obligate intracellular parasites containing a DNA or RNA core in a protein capsid.
History of Microbiology and Cell Theory
Cell Theory: All living organisms are composed of cells that arise from pre-existing cells (Hooke, van Leeuwenhoek, Virchow).
Biogenesis vs. Spontaneous Generation:
Spontaneous generation: Claimed life arises from nonliving matter.
Biogenesis: Proved life comes only from pre-existing cells, definitively disproved by Pasteur's swan-neck flask experiment.
Golden Age of Microbiology and Germ Theory
Fermentation & Pasteurization: Pasteur demonstrated microbial fermentation and developed pasteurization to eliminate spoilage organisms.
Germ Theory Milestones: Jenner (vaccination), Semmelweis (handwashing), Pasteur (vaccines/attenuation), and Koch (Koch's postulates linking specific microbes to diseases).
Emerging Infectious Diseases
Categories: New diseases (COVID-19, Ebola), mutations (MRSA, H1N1), geographical shifts (Zika), and resurgent diseases (measles).
Factors: Population growth, agricultural expansion, antibiotic overuse, global travel, and ecosystem disruption.