Discovery of Microbes: Antonie van Leeuwenhoek (1670s) first observed “animalcules” with simple microscopes.
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Germ Theory of Disease: Louis Pasteur and Robert Koch established the role of microbes in fermentation and infectious diseases.
Koch’s Postulates: Criteria linking a microorganism to a specific disease.
Golden Age of Microbiology (1850–1900): Rapid advances in bacterial isolation, staining, and identification.
Modern Microbiology: Integration of molecular biology, genomics, and biotechnology into microbial research.
Major Groups of Microorganisms
Bacteria – Prokaryotic, un icellular organisms with diverse metabolic capacities.
Archaea – Prokaryotes distinct from bacteria, often extremophiles.
Viruses – Acellular entities requiring host cells for replication.
Fungi – Eukaryotic organisms including yeasts and molds, important decomposers.
Protozoa – Unicellular eukaryotes, often motile, some pathogenic.
Algae (microalgae) – Photosynthetic eukaryotes, important for oxygen production and as primary producers.
Fundamental Characteristics of Microorganisms
Size and Simplicity: Microscopic, often unicellular, with rapid growth and reproduction.
Metabolic Diversity: Microbes can be autotrophic, heterotrophic, chemolithotrophic, phototrophic, aerobic, or anaerobic.
Reproduction: Mainly binary fission in prokaryotes, budding in yeast, and complex life cycles in protozoa and fungi.
Genetic Plasticity: High mutation and horizontal gene transfer rates provide adaptability.
Omnipresence: Found in soil, water, air, extreme environments, and within host organisms.
Microbial Structure and Function
Prokaryotic Cell Structure: Cell wall (peptidoglycan in bacteria), plasma membrane, ribosomes, nucleoid, plasmids, flagella, pili.
Eukaryotic Microbes: Nucleus, organelles (mitochondria, ER, Golgi, vacuoles).
Viruses: Protein capsid, nucleic acid (DNA or RNA), some with envelopes.
Microbial Nutrition and Growth
Nutritional Requirements: Carbon, nitrogen, sulfur, phosphorus, trace elements, growth factors.
Modes of Nutrition: Autotrophs (photoautotrophs, chemoautotrophs) vs. heterotrophs.
Environmental Influences: Temperature (psychrophiles, mesophiles, thermophiles), pH (acidophiles, alkaliphiles), oxygen (aerobes, anaerobes, facultative).
Growth Curve: Lag, log, stationary, and death phases.
Microbial Genetics
DNA replication, transcription, and translation in microbes.
Gene regulation (operon model).
Horizontal gene transfer: transformation, conjugation, and transduction.
Role of plasmids and bacteriophages in genetic exchange.
Microbial Ecology
Role of microbes in nutrient cycling (carbon, nitrogen, sulfur, phosphorus cycles).
Symbiotic relationships (mutualism, commensalism, parasitism).
Microbial communities in soil, water, and extreme environments.
Microbiomes (gut microbiota in humans and animals).
Applied Microbiology
Medical Microbiology: Pathogenesis, host–pathogen interactions, antibiotics, vaccines.
Industrial Microbiology: Fermentation, antibiotics, enzymes, biofuels.
Agricultural Microbiology: Nitrogen fixation, biocontrol, soil health.
Environmental Microbiology: Wastewater treatment, biodegradation, bioremediation.
Food Microbiology: Fermented foods, food spoilage, food safety.
Importance of Microbiology
Scientific Importance: Model organisms in genetics and molecular biology.
Ecological Importance: Essential for global ecosystems and climate regulation.
Economic Importance: Pharmaceutical, food, agriculture, and biotechnology industries.
Human Health: Understanding pathogens, developing therapies, probiotics, and vaccines.
