Overview
This lecture introduced the basics of microbiology, including the types of microbes, classification methods, laboratory techniques, and key historical discoveries relevant to microbes and medical science.
Introduction to Microbiology & Microbes
- Microbiology is the study of microorganisms too small to be seen with the naked eye.
- Microbes include bacteria, archaea, viruses, fungi, protozoa, and parasitic worms (whose eggs/larvae are often microscopic).
- Pathogens are microbes that cause disease.
- Parasitic worms (multicellular) and protozoa (unicellular) are major groups of pathogens.
Cell Types & Classification
- Prokaryotes (bacteria, archaea) lack a true, membrane-bound nucleus and organelles.
- Eukaryotes (fungi, protists, animals, plants) have membrane-bound nuclei and organelles.
- Viruses and prions are non-cellular; prions are misfolded proteins.
Importance and Uses of Microbes
- Over 70% of atmospheric oxygen is produced by photosynthetic microbes (mainly algae).
- Microbes are essential for decomposition and nutrient cycling.
- Microbes are used in biotechnology, fermentation (bread, beer, wine), and production of medicines (e.g., insulin).
- GMOs do not transfer genetic material to consumers; real risk is gene transfer to wild plant populations.
Disease and Pathogens
- Not all diseases are caused by microbes; heart disease and cancer often have non-microbial causes.
- Some microbes are always pathogenic (e.g., influenza virus); others are opportunistic pathogens (e.g., Staphylococcus).
The Scientific Method & Historical Figures
- The scientific method involves hypothesizing, experimenting, and forming theories.
- Louis Pasteur disproved spontaneous generation and developed pasteurization.
- Robert Koch developed methods to identify disease-causing microbes (Koch’s postulates).
- Handwashing and antiseptic techniques were pioneered by Holmes, Semmelweis, and Lister.
Taxonomy & Naming of Microbes
- Binomial nomenclature: genus (capitalized) + species (lowercase), e.g., Escherichia coli.
- Taxonomic hierarchy: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
- Three domains: Bacteria, Archaea, Eukarya.
Laboratory Techniques & Media
- The "Five I’s" in microbiology lab: Inoculation, Incubation, Isolation, Inspection, Identification.
- Sterile means free from all life forms.
- Types of media: general purpose, enriched (has required growth factors for fastidious organisms), selective (allows some microbes to grow), differential (shows visible differences).
- Agar is a solidifying agent in culture media.
- Colony: cluster of microbes from a single cell, used to start pure cultures.
Microscopy & Staining
- Light passes from the bulb, through specimen, objective lens (real image), and ocular lens (virtual image).
- Total magnification = objective lens x ocular lens (ocular lens usually 10x).
- Oil immersion prevents light refraction at high magnification.
- Wet mounts (live cells), heat fixing (kills/adheres cells), basic stains (positive charge, bind to cell), acidic stains (negative charge, stain background).
- Simple stains use one dye for contrast; differential stains distinguish structures or cell types.
Key Terms & Definitions
- Microbe — a microscopic organism.
- Pathogen — a microbe that causes disease.
- Prokaryote — cell lacking a nucleus (bacteria, archaea).
- Eukaryote — cell with a true nucleus (fungi, animals, plants).
- Binomial nomenclature — two-name system for species classification.
- Fastidious organism — requires specific nutrients for growth.
- Selective media — allows only certain microbes to grow.
- Differential media — shows differences between microbes (e.g., color change).
- Colony — visible group of microbes derived from a single cell.
- Pure culture — culture containing only one type of microorganism.
Action Items / Next Steps
- Review types and uses of laboratory media.
- Practice writing and recognizing binomial nomenclature.
- Memorize the order of taxonomic ranks and the three domains.
- Learn microscope parts and calculation of total magnification.
- Prepare for lab exercises on streak plate technique and identifying colony types.