Chapters 1 & 10 Flashcards
Microbiology
The study of “small organisms,” which are usually invisible to the naked eye; 20 nanometers: smallest virus - 3-4 um, largest - protozoans
Microbes
General term encompassing microorganisms and viruses; diverse in terms of their appearance, metabolism, physiology, reproduction, and genetics. Ex. bacteria, viruses, protist, fungi, helminthes (larva stages - parasitic worms)
Leeuwenhoek (1632-1723)
- Inventor of the first microscope, which could magnify objects up to 300X
- First to use microscopes to observe microorganisms in pond water (1674), which he called “animacules”
- Created detailed descriptions of his findings (pond water, plants, insects, tooth scrapings, etc.) over the next 50 years
- Considered to be the “father of microbiology”
Robert Hooke
Fist to describe “cellulae” (small rooms) in cork in 1665, which led to the formulation of the cell theory by others
Matthias Schleiden and Theodor Schwann
Independently published statements that “cells are the basic organizational unit of all living things” - The Cell Theory (1800s)
Spontaneous Generation
The discredited belief that organisms could arise from non-living matter (worms on meat/rats from hay)
Biogenesis
All living cells arise from other pre-existing living cells
Science
An organized body of knowledge about the natural world
Scientific Method
A series of steps used to gain information about the natural world:
- Make an observation/identify a problem
- Gather information about observation/problem
- Formulate a hypothesis (educated guess)
- Conduct a controlled experiment: contol group, experimental group, collect data
- Conclusion: does your data support or refute the hypothesis
- Peer review
The Progression of Scientific Ideas
- Ideal hypothesis is generated
- Experimentation: hypothesis confirmed or rejected
- Peer review/Publication
- If published, scientific community conducts further experimentation
- If experimental data is consistent and reliable then, with time, the original hypothesis becomes a theory
- Consistently supported theories, over long periods of time, can be elevated to scientific law or a constant fact of nature
Francisco Redi
In 1668, he covered rotting meat with fine gauze, showing that maggots developed only in meat that flies could reach to lay eggs; spontaneous generation would not be refuted for another 200 years because many insisted that only spontaneous generation of microorganisms was disproved
Needham’s Hypothesis, Experiment, and Conclusion
- He boiled chicken broth, put it in a flask, and sealed it
- If microbes grew, then it could only be because of spontaneous generation
- Microbes grew, but we now know this was because the flask was not sterilized before adding the broth
Spallanzani’s Hypothesis, Experiment, and Conclusion
- He put broth in a flask, boiled it, and sealed it creating a vacuum (no air)
- No microbes in the cooled broth
- Critics said he didn’t disprove spontaneous generation, only that it required air
Louis Pasteur’s Experiments
- Argued against spontaneous generation; allowed the free passage of air, but prevented the entry of microbes
- Boiled meat broth in a flask which sterilized it; swan neck flask created a seal with water and bacteria
- No microbes developed until flask was tilted so some broth flowed into the curved neck
- Gravity had caused microbes to settle at the low point of the neck, never reaching the base until washed in with the broth
- Could not be replicated by other scientists who used vegetable broth which contains many endospores; original experiment used meat broth (luck) which contains few endospores
John Tyndall
Explained the conflicting results of Pasteur’s experiments, and proved him correct; He concluded that some microorganisms exist in two forms:
- a cell form that is easily killed by boiling
- a cell form that is heat resistant: endospores
3 Things Proved by Pasteur’s Experiments
- No living things arise by spontaneous generation
- Microbes are everywhere (even in air and dust)
- The growth of microbes causes dead plant and animal tissue to decompose and food to spoil (led him to develop the technique of pasteurization which kept wine from spoiling)
*Also contributed to the development of vaccines
Germ Theory of Disease (late 1800s)
Microbes cause disease, and specific microbes cause specific diseases; previously thought to be caused by “bad air” or linked to superstitions or religion (punishment)
Ignaz Semmelweis (1850)
- Noted that the rate of childbirth infections were greater at teaching clinics than when staffed by midwives
- Doctors went from mother to mother - microbes from infected patients could spread to other patients
- Midwives only worked with one patient
Joseph Lister
- Believed pus around wounds was caused by microorganisms and that if they were killed the wounds might heal faster
- Dressed wounds in phenol soaked cloths, reducing the rate of infection and speeding up the healing process
- Proposed and practiced the idea of antiseptic surgery (sprayed phenol of the patients)
- Phenol is not only toxic to most microorganisms, but humans as well (powerful carcinogenic); no longer used as an antiseptic
Robert Koch (late 1870s)
- Studied anthrax: disease of cattle/sheep but also in humans
- Observed that microbes were present in all blood samples of infected animals
- Isolated and cultivated these microbes (Bacillus anthracis)
- Injected healthy animal with cultured bacteria and it became infected; blood sample showed same microbes
- Proved that particular microbes cause particular diseases