Ch1: Intro to Micro

What is Microbiology?

  • Microbiology is the study of organisms too small to see with the naked eye.

  • Visual cues from slides include various microscopic forms:

    • Bacteria (single-celled organisms)

    • Viruses (acellular entities that require a host cell to replicate)

    • Fungi (complex organisms, can be unicellular or multicellular)

    • Protozoa (single-celled eukaryotes, historically grouped with protozoans)

    • Algae (photosynthetic organisms, includes single-celled forms)

    • Pseudopods (temporary projections of a cell used by some amoeboid cells)

    • HIV (listed among examples of microbes; note: HIV is a virus)

Why Should We Care About Microbiology?

  • Microbiology is relevant across multiple contexts demonstrated by real-world roles:

    • A parasite specialist examines leaf litter to detect black-legged ticks, the carriers of Lyme disease.

    • A geomicrobiologist from NASA collects samples from Mono Lake to study survival strategies of extreme bacteria in environmental conditions.

    • A bacteriologist checks cultures of genetically modified bacteria for growth, illustrating applications in energy research and biotechnology.

  • These scenarios illustrate the breadth: public health, environmental science, and biotechnology.

Microbial Groups at a Glance

Viruses

  • Acellular (no cellular structure) and obligate parasites (must live inside a host to survive).

  • Replicate only when they are inside a living host cell.

Bacteria

  • Single-celled and highly diverse.

  • Eubacteria are more common and are involved in human disease.

  • Archaea live in harsh environments.

Protists

  • Includes Protozoans and Algae.

  • Complex single-celled organisms.

  • Algae and protozoa are considered potential ancestors to modern plants (algae) and animals (protozoa) and fungi (through slime molds).

Fungi

  • Complex uni- or multicellular organisms.

  • Absorb organic chemicals for energy.

  • Nonmotile organisms producing sporangia (asexual structures that release spores).

Fungal Example

  • Pathogenic Fungus Attacks a Parasitic Plant: Fusarium oxysporum is a potent pathogen of witchweed (Striga), a parasitic plant that attacks crops.

  • Fungal spores shown in blue; fungal filaments in tan.

Animals

  • Complex multicellular organisms.

  • Eat organic compounds for energy.

  • Motile organisms.

  • Scolex: the structure that anchors the tapeworm to the host’s intestinal wall.

A Very Brief History of Microbiology

  • The Unknown

  • The Cell

  • Refute Spontaneous Generation

  • Germ Theory

  • DNA Technology

The Unknown

  • Ancient indigenous peoples used microbes in medicine and food.

  • Egyptians documented beer and wine-making.

  • Greeks described transmissible diseases, pointing to the existence of microbes.

The Cell

  • 1665 – Robert Hooke: organisms are composed of cells.

  • 1673–1723 – Antoni van Leeuwenhoek: first to see microbes under microscopes.

Refuting Spontaneous Generation

  • Francesco Redi (1668) first disproved spontaneous generation via controlled experiments with meat and jars.

  • Louis Pasteur (1861–1864) showed microorganisms arise only from other microorganisms; disproved spontaneous generation with swan-neck flask experiments (demonstrating that air alone does not generate life).

Disproving Spontaneous Generation: Redi’s Experiment

  • Jar 1: Meat exposed to air with no protection (exposed to flies) – maggots form in the meat.

  • Jar 2: Meat exposed to air but covered with a fine cloth – no maggots form.

  • Jar 3: Meat not exposed to air or flies – no maggots form.

  • Conclusions: Maggots come from flies, not spontaneously from meat.

Pasteur’s Experiment (Robust Evidence Against Spontaneous Generation)

1) Create flasks of nutrient medium with “swan” necks open to air but excluding microbial dust.
2) Boil to sterilize and kill microorganisms in the medium.
3) Break the swan neck off one flask, exposing contents to dust-borne microbes; dust settles in the bend and microbial life grows.
4) The sterile (lifeless) flask shows no microbial growth.

Germ Theory and Key Milestones

  • Germ Theory: Specific microbes cause specific diseases.

  • Jenner (1796): Vaccination using cowpox provides immunity to smallpox; question of whether it was his idea is noted but not essential here.

  • Koch (1876): Koch’s Postulates—link specific microbes to specific diseases.

  • Fleming (1928): Discovered penicillin; antibiotics transformed medicine; debate about who was the first to discover antibiotic properties is noted.

The First Vaccine and Smallpox Eradication

  • Timeline: 1950–1980 saw the spread and eventual eradication of smallpox.

  • 1965: Vaccine campaign began.

  • 1979: Smallpox eradicated; 1980: official eradication recognition.

  • Visualization: A chart shows “Countries Reporting Smallpox” with values reaching 0 by 1980 after campaigns.

Observing Microbial Growth and Antibiotics

  • The Accidental Discovery of Antibiotics: Penicillin was discovered by accident; Penicillin is an antibiotic secreted by the fungus Penicillium.

  • Antibiotics became crucial for treating widespread bacterial infections (e.g., gangrene, tuberculosis, syphilis).

  • The variable regions around antibiotic samples reflect differential effectiveness; bigger zones indicate more effective antibiotics.

Fleming and Penicillin

  • Fleming observed that Penicillium fungus produced penicillin, which killed Staphylococcus aureus.

  • In the 1940s, penicillin was clinically tested and mass-produced.

Penicillin Resistance and Cheese Varieties

  • Penicillium is a green mold; some species produce penicillin.

  • Penicillium camemberti and Penicillium roqueforti are responsible for the flavors of Camembert and Roquefort cheeses.

DNA Technology: Foundations and Milestones

  • 1953 – Watson and Crick solved the structure of DNA with data from Rosalind Franklin.

  • 1972 – Boyer and Cohen pioneered Recombinant DNA Technology; first to cut and paste DNA.

    • Used restriction enzymes to cut DNA at specific sequences.

    • By combining bacterial plasmids (small circular DNA) with foreign DNA, created recombinant DNA with new sequences not found in nature.

Rosalind Franklin and the DNA Model

  • Rosalind Franklin was an X-ray crystallographer whose famous Photo 51 revealed the helical structure of DNA.

  • Watson and Crick used her data—without her direct permission—to build the double-helix DNA model in 1953.

Watson and Crick: The Double Helix Model

  • They built the first correct 3D model of DNA in 1953, showing the double helix with sugar-phosphate backbones on the outside and bases paired in the center.

  • Earlier, they incorrectly placed phosphates on the inside; Franklin’s X-ray data helped them realize backbones must be on the outside.

How Microbes Are Classified

  • Taxonomy: classification of organisms by physical traits.

  • Systematics: uses phylogeny (evolutionary history); uses both physical and molecular traits.

  • Binomial Nomenclature: naming using genus and species (two-part name).

Taxonomy and Nomenclature Basics

  • Taxonomy: classification by physical traits; hierarchical; aids identification; provides universal names.

  • Binomial Nomenclature: genus + species (italicized in print; e.g., Klebsiella pneumoniae).

  • Pronunciation guides and etymology are often included to aid learning.

Examples of Nomenclature (selected entries)

  • Klebsiella pneumoniae (bacterium) — kleb-sē-el'lä nü-mō'nē-ī

  • Pfiesteria piscicida (dinoflagellate) — fes-ter'ē-ä pi'si-si-dä

  • Salmonella typhimurium (bacterium) — sal-mōn-el'lä tī-fi-mur'ē-um

  • Streptococcus pyogenes (bacterium) — strep-tō-kok'kus pi-äj'en-ēz

  • Saccharomyces cerevisiae (yeast) — sö-kä-rō-mī'sēs se-rē-vī'sē-ī

  • Penicillium chrysogenum (fungus) — pen-i-sil'lē-um krī-so'jen-um

  • Trypanosoma cruzi (protozoan) — trī-pä-nō-sō'mä krū-z'ē

The Five Kingdom System (Overview)

  • PLANTS (Kingdom Plantae)

  • FUNGI (Kingdom Myceteae)

  • ANIMALS (Kingdom Animalia)

  • PROKARYOTES (Kingdom Monera)

  • EUKARYOTES (contextual grouping for kingdoms within?)

  • Representative groups by kingdom include:

    • Plants: ferns, mosses, seed plants (gymnosperms, angiosperms)

    • Fungi: Basidiomycetes, Ascomycetes, Zygomycetes

    • Animals: Arthropods, Chordates, Mollusks, Annelids, Echinoderms, etc.

    • Protists (Kingdom Protista): Diatoms, Dinoflagellates, Ciliates, Amoebas, etc.

    • Monera (Prokaryotes): Archaea and Bacteria (early cells)

  • Timeline milestones:

    • First cells appeared about 3.5imes109extyearsago3.5 imes 10^9 ext{ years ago}.

    • First multicellular organisms appeared about 0.6imes109extyearsago0.6 imes 10^9 ext{ years ago}.

    • First eukaryotic cells appeared about >2 imes 10^9 ext{ years ago}.

The Three-Domain System (Overview)

  • DOMAIN BACTERIA: Bacteria (prokaryotes)

    • Examples: Gram-positive endospore formers, cyanobacteria, spirochetes, etc.

  • DOMAIN ARCHAEA: Archaea (prokaryotes that live in extreme environments, e.g., extreme salt or extreme heat)

  • DOMAIN EUKARYA: Eukaryotes (plants, animals, fungi, protists)

  • The system also lists higher-level associations:

    • KINGDOM PLANTAE, KINGDOM ANIMALIA, KINGDOM FUNGI within the Eukarya domain, and various groups within Bacteria and Archaea.

  • Ancestral Cell Lines listed as part of the discussion of the origin of life and the evolution of cellular life.

If you want, I can reorganize these notes into a single continuous outline or tailor them to a specific exam focus (e.g., emphasis on history, taxonomy, or molecular biology).