Intro To Microbiology
What is Microbiology?
Study of microscopic living organisms (microorganisms).
Includes bacteria, archaea, protozoa, fungi, algae; sometimes viruses.
Focus: structure, function, diversity, evolution; roles in the world, in the body, in animals/plants.
Microorganisms underpin nearly all biological processes; fundamental to biology.
Major Groups of Microorganisms
Viruses: acellular; not cells; require a host to reproduce; genetic material DNA or RNA; can be pathogenic.
Bacteria: prokaryotes; unicellular; cell walls often with peptidoglycan; diverse habitats; some pathogens.
Archaea: prokaryotes; distinct from bacteria; often extremophiles.
Fungi: eukaryotes; can be unicellular or multicellular; cell walls with chitin; includes yeasts and molds; some pathogens and antibiotic producers (e.g., penicillin).
Protozoa: eukaryotes; mostly unicellular; often motile; includes parasites.
Algae: eukaryotes; can be unicellular or multicellular; photosynthetic; cell walls cellulose.
Note: viruses are often treated separately due to acellular nature.
Prokaryotes vs Eukaryotes
Prokaryotes (Bacteria, Archaea):
No membrane-bound nucleus.
Usually unicellular; single circular chromosome.
Often have surface Appendages for motility.
Peptidoglycan cell walls (in bacteria).
Eukaryotes (Protozoa, Fungi, Algae):
Nucleus with membrane (membrane-bound).
Can be unicellular or multicellular.
Microbes in Food Production
Fermentation: sugars converted to ethanol, gases, and organic acids.
Key players: Aspergillus, Lactobacillus, Saccharomyces.
Products: soy sauce, cheese, yogurt, beer, wine, bread.
Concept: microbial metabolism drives food transformation.
The Microbiome and Host Relationships
Microbiome: microbes associated with normal human tissues.
Commensal relationship: microbes that do not harm the host.
Microbes contribute to digestion, metabolism, immune function, and overall health.
Taxonomy and Nomenclature
Binomial nomenclature: genus + species; two-part name; italics; genus capitalized, species lowercase.
Examples: Homo sapiens, Escherichia coli, Bacillus anthracis, Chlamydia trachomatis, Lactobacillus lactis, Mycobacterium tuberculosis, Yersinia pestis.
Molecular Phylogeny and the Three Domains
Molecular genetics enables phylogenetic analyses (e.g., 16S rRNA for prokaryotes).
Three domains: Bacteria, Archaea, Eukarya.
Prokaryotes: Bacteria and Archaea.
Eukaryotes: animals, plants, fungi, protists, etc.
Abundance and Harmlessness of Microbes
Most microbes are harmless.
Skin: ~3 × 10^9 bacteria per cm^2.
Large intestine: 400–1000 types of bacteria.
Microbes outnumber human cells by about 10-to-1 in the human body.
Quick Recall: Largest to Smallest
Order from largest to smallest: Red blood cell, bacterium, virus.
Sizes (typical):
Red blood cell:
Bacterium:
Virus: