Antoni Van Leeuwenhoek
- first to understand microscopic/microorganisms
- began using simple microscopes
- examined water and saw fungi, algae, and bacteria, called them “animalcules”
-animalcules were called microorganisms by the end of the 19th century
Carolus Linnaeus
- developed taxonomic system
- six categories
What are the six categories of Carolus Linnaeus’s taxonomic system
- fungi 2. protozoa 3. algae 4. bacteria 5. archaea 6. small multicellular animals
Fungi, protozoa, algae
eukaryotic but microorganisms
Bacteria and Archaea
prokaryotic cells and microorganisms
Archaea
-more closely related to eukaryotes but look like bacteria
-normally live in harsh environments
Fungi characteristics
- eukaryotic, contain a nucleus
- have cell walls and obtain food from other organisms
- composed of molds: multicellular, grow as long filaments that intertwine
- reproduce sexually and asexually - composed of yeasts: unicellular, oval or round
- repoduce asexually though budding, some produce sexual spores
Protozoa characteristics
- single-celled eukaryotes
- similar to animals in nutritional needs, cell structure
-live freely in water or animal hosts - most asexual, some sexual
How are protozoa categorized
- by their locomotion
- pseudopodia: cell extensions that flow in direction of travel
- cilia: numerous, short, protrusions that propel through regular beating
-flagella: fewer than cilia, but longer and more whiplike
Algae characteristics
- uni or multicellular photosynthetic organisms
- categorized on basis of pigmentation, storage products, and cell wall composition
- large algae= seaweed and kelp (derive agar)
-unicellular algae are common in freshwater, streams, lakes, pones, oceans - serve as major food for aquatic/marine animals
Bacteria and Archaea characteristics
- unicellular and lack nucleus
- much smaller than eukaryotes (= mitochondria size)
- asexual reproduction
- bacteria cell walls are composed of peptidoglycan
- archaea cell walls lack peptidoglycan
- live in almost every habitat that contains enough moisture (pairs, clusters, single, chains)
- 1 single bacteria cells can contain 100s of viruses
What is the difference between the cell walls of bacteria and archaea
Bacteria cell walls are composed of peptidoglycan and archaea cell walls are not
During the Golden age of microbio, what four questions did scientists want to answer?
- Is spontaneous generation of microbial life possible
- What causes fermentation?
- What causes disease?
- How can we prevent infection and disease?
Aristotle
- proposed spontaneous generation
What is spontaneous generation?
The idea that living things can arise from nonliving/inanimate matter (350BC)
Francisco Redi
- late 1600s
- demonstrated that when decaying meat was isolated from fleas, no maggots developed
- as a result, scientists began to doubt Aristotle (used science to change ideas over a long period of time)
- dependent variable: maggots or no maggots
- independent variable: uncovered, covered, or gauzed covered jar
Needham
- expanded on Redi’s experiment but included bacteria after Leeuwenhoek’s discovery of them
- believed microbes did arise spontaneously
- boiled beef gravy and placed in jars (covered and uncovered)
- covered jar still appeared cloudy
- led to ‘proof’ of spontaneous generation
- later found out that he did not boil beef gravy long enough to kill all life
Spallanzani
- concluded that Needham did not boil beef gravy long enough
- did the same experiment but increased boiling time and sealed jar tightly
- no life was evident in either jar; spontaneous generation was debunked
- critics argued that too tightly sealed of a jar did not allow air flow for life
critics argued that prolonged heating destroyed “life force”
What was the main difference between Needham’s and Spallanzani’s experiments?
Spallanzani boiled the beef gravy for a longer time, and tightly sealed the covered jar
What were the critics of Spallanzani’s experiment?
- prolonged heating destroyed life force
- too tight of a seal did not allow enough air flow
Louis Pasteur
-debunked spontaneous generation
- used swan-neck flasks to allow air flow into beef gravy
- boiled beef gravy long enough to kill all bacteria
- no dust in gravy showed no life but dust in gravy appeared cloudy
- concluded that microbes arise from microbes in the air/dust
Why were the swan-necked flasks critical in Pasteur’s experiment?
it allowed for airflow into the beef gravy but prevented dust from settling into it
Scientific method
observation, hypothesis, experiments, observed results, accept or reject hypothesis
What causes disease?
-prior to 1800s attributed to evil spirits, astrology, imbalances, foul vapors
- Pasteur’s discovery that microbes led to spoiling wine led to hypothesis that they are also responsible for disease
- many people still did not believe germs caused disease
