study guide 1

Microbiology

The study of microscopic (microorganisms) living things (like bacteria, virus, fungi, and Protozoa) and how they affect humans, animals, plants, and the environment. Including their classification, physiology, genetics, roles in nature, and impact on humans (both beneficial and harmful).

Microbe

A tiny living organism (or virus) too small to see without a microscope. A general term for microscopic organisms , including bacteria, archaea, fungi, protists, viruses, and helminth eggs/larvae

Louis Pasteur

French scientist (1822-1895) known for disproving spontaneous generation with his swan-neck flask experiment, showed microbes cause fermentation and spoilage, and provided key evidence for the germ theory of disease.

Developing pasteurization, and showing that microbes cause disease.

 

Robert Koch

German physician (1843-1910) who developed koch's postulates to prove specific microbes cause specific diseases. (proved tuberculosis, anthrax, and cholera).

Koch’s postulates

A set of steps used to show that a particular microbe causes a particular disease.

1. Microbe present in every disease case, absent in healthy individuals.

2. Must be isolated and grown in pure culture

3. Healthy host infected with in must develop the same disease

4. Must be re-isolated and math the original microbe

Phylogeny

The “family tree” of life that shows how organisms are related through evolution. The study of evolutionary relationships between organisms. Modern microbiology uses molecular data (DNA, RNA, proteins) to build the "Tree of life".

rRNA

A type of RNA found in ribosomes; used to compare different organisms and figure out evolutionary relationships. Molecular marker used in taxonomy. Carl Woese and George Fox used small subunit rRNA sequences to discover Archaea and propose the three-domain system (bacteria, archaea, eukarya)

 

Binomial nomenclature

The two-part scientific naming system for living things created by Linnaeus. (Genus/apitalized + species/lowercases) ex. Escherichia coli → E. coli.

 

Prokaryote

Unicellular organism without a nucleus or membrane-bound organelles. A simple cell without a nucleus (bacteria and archaea)

 

Eukaryote

• Eukaryotic (have a nucleus & membrane-bound organelles).

Includes all multicellular organisms + many unicellular ones.

• Subgroups:

Animals, plants, fungi, Protists (e.g., ciliates, amoebas, slime molds).

Bacteria

• Unicellular, prokaryotic (no nucleus).

• Cell walls: contain peptidoglycan.

Shapes: Coccus (spherical), Bacillus (rod), Vibrio (comma), Spirillum (rigid spiral), Spirochete (flexible spiral).

• Metabolism:

Photosynthetic: cyanobacteria, green sulfur, green nonsulfur.

Non-photosynthetic: use organic/inorganic compounds.

• Roles: beneficial, neutral, or pathogenic.

cocci - bacteria shape

Spherical

Bacillus

Rod

Vibrio

Comma

Spirillum

Rigid spiral

Archaea

• Also prokaryotic, but genetically distinct from bacteria.

• No peptidoglycan in their cell walls.

• Often live in extreme environments (extremophiles).

• Unique membrane lipids.

Examples:

Methanogens → produce methane (important in digestion & climate).

Halophiles → thrive in high salt.

Thermophiles → thrive in high heat (hot springs, hydrothermal vents).

Fungi

• Eukaryotes with chitin cell walls, non-photosynthetic.

• Cell walls: made of chitin.

• Yeasts (unicellular): e.g., Candida albicans → yeast infections, oral thrush.

• Molds (multicellular): decomposers; can cause allergies/mycotoxins; source of antibiotics (penicillin) & drugs (cyclosporine).

 

Virus

Non-cellular infectious agent. Require host cells to replicate. Consist of genetic material (DNA or RNA) surrounded by protein (sometimes lipid envelope). Not included in the tree of life.

 

Leeuwenhoek

(Antonie van Leeuwenhoek)

Dutch tradesman known as the "Father of microbiology"

• Originally a fabric seller in Delft, Netherlands; became skilled in lens-making.

• Built powerful simple microscopes (one lens, but superior clarity).

• 1674: First to observe and describe single-celled organisms → called them “animalcules” or “wee little beasties.”

• His reports to the Royal Society were first doubted but later confirmed → gained fame.

Spontaneous generation

Definition: the belief that life arises from nonliving matter.

Disproved by pasteur's swan-neck flask experiment. Replaced by biogenesis: life comes only from existing life.

Aristotle (384-322 BC):

• Proposed life arises if material contains pneuma (spirit/breath)

• Evidence: sudden appearance of fish in puddles, etc.

Middle ages -> 17th century: widely accepted

• Frogs appearing after Nile floods

• Mice appearing in grain stores

• Jan Baptista Van Helmont: claimed mice came from rags + wheat in 3 weeks.

 

Endosymbiotic theory

Mitochondria and chloroplasts originated from prokaryotic cells (bacteria) living symbiotically inside ancestral eukaryotes. Supported by their bacterial-like DNA, ribosomes, and division by binary fission.

 

Germ theory of disease

The theory that microorganisms cause disease