Lecture One: Intro/History/Microscopy/Taxonomy/Phylogeny Flashcards
Animalcule
“tiny” eggs Antonie van Leeuwenhoek found on rotten mean
Discovered using a simple microscope
Microscopic organisms (archaic term)
Antisepsis
The practice of using antiseptics to eliminate the microorganisms that cause disease.
Joseph Lister sprayed carbolic acid (phenol) on surgical wounds and their rate of infection decreased
His work popularized surgical antisepsis to reduce perpetual fever
Archaea (Domain)
A type of single-celled organisms
Do not have nuclei or organelles
Differs from Bacteria in that they do not contain peptidoglycan
Brightfield (Microscopy)
[What it is…; Looks like…; Why it is useful…; Good for…]
A way of using a compound microscope;
What it is: Basic light microscopy
Looks like: bright background, cells almost invisible, but pigments and stained objects are dark and colored
Why it is useful: it is the least expensive way to see truly tiny objects like bacterial cells.
Good for: observation of stained (dead) specimens
or very pigmented live organisms
(not most bacteria)
Histology, Gram staining, looking at large algae in pond water
magnification = up to 1,000x
resolution = 0.2μm or worse
Inexpensive and easy to use up to 1000X
Broth
A liquid medium containing proteins and other nutrients for the culture of bacteria.
Needham used boiled mutton broth to see if animalcules arose from vital force.
Pasteur used boiled broth and found it would only rot if it was exposed to air and/or the trapped dust in the swan neck flask
Cell Theory
[Three major points]
- All cells come from other cells
- Cells are the smallest unit of life
- All living organisms are made of cells
Cholera
an acute diarrheal illness caused by infection of the intestine with Vibrio cholerae bacteria
John Snow studied the biggest case in London in 1854 (beginning of modern-day epidemiology)
Residents blamed miasma / John Snow found it was fecal matter from infected baby and the source was a local water pump
Authorities refused to believe since it was gross so they stuck with miasma
Pasteur also tried working with it, but could not get pure culture, and did not mean Koch’s postulates
Compound Microscope
A microscope used for viewing samples at high magnification (40 - 1000x), which is achieved by the combined effect of two sets of lenses: the ocular lens (in the eyepiece) and the objective lenses (close to the sample).
Use visible light
Existed in the 1600’s but glass manufacturing was lacking
has a resolution of 0.2μm at best
Darkfield (Microscopy)
[What it is…; Looks like…; Why it is useful…; Good for…]
A way of using a compound microscope;
What it is: Condenser contains opaque disc that blocks direct light, but allows light reflected from specimen to enter. Specialized objectives must be used.
Looks like: dark background, bright cells
Why it is useful: provides extra contrast even without stains: especially for certain live microorganisms that can’t be seen with brightfield.
Good for: examining unstained, living microorganisms for size, shape, motility
magnification = up to 1,000x resolution = 0.2μm or worse
Epidemiology
The study of disease patterns
The swan-neck flask was the end of believing in “spontaneous generation” but epidemiology was around before the creation of the flask.
Ignaz Semmelweis: Obstetrician at a Vienna General Hospital teaching hospital.
Modern epidemiology began with modern cholera and John Snow
Eukarya / eukaryote (domain)
Animals, fungi, and plants are examples
Single cells that have nuclei and organelles are all found in the domain Eukarya
Most “modern” eukaryotes have mitochondria, which share a common ancestor with proteobacteria!
Evolutionary Distance
Lines used to measure the distance between two species / specimens.
When using horizonal lines, only count the number of horizonal lines; length does not matter
Length does matter when using phylogenetic trees
Fluorescence (Microscopy)
[What it is…; Looks like…; Why it is useful…; Good for…]
A way of using a compound microscope; much more common today in research than any of the others we’ve seen so far
What it is: microscopy where one color of light “excites” molecules (fluorochromes) that emit a different color. Special filters prevent us from seeing the first “excitation” color, so only the second, emitted color is visible. (special proteins have this fluorescence property)
Looks like: dark background, brightly glowing colored spots
Why it is useful: It is very specific: only the special pigments/proteins are visible. Scientists can use this to find very specific structures within cells.
Good for: observation of specimens stained (usually dead but not always) using fluorescent pigments, or transgenically producing fluorescent proteins
magnification = up to 1,000x resolution = 0.2μm or worse
Very expensive
Fly (insect)
Specimens used in Francesco Redi’s experiment on spontaneous generation
Redi believed maggots spawn from adult flies
Maggots only appeared in open containers with meat in them
Germ Theory of Disease
States that infectious diseases are caused by microorganisms.
Robert Koch provided great evidence in favor of the Germ Theory of Disease through the injecting of diseased blood into rats
Gram Stain
A method of staining used to classify bacterial species into two large groups: Gram-positive and Gram-negative
Gram-positive bacterial cell (thick peptidoglycan) moves from purple to blue-purple when method is complete
Gram-negative bacterial (thin peptidoglycan) cell moves from purple to orange-red when method is complete
Crystal violet (Gram Stain)
The first step in the gram stain method
A positive charged dye that adheres to the cell wall of all cells
Turns both gram-positive and gram-negative cells purple
Iodide (Gram Stain)
The second step in the gram stain method
Added as a mordant to form the crystal violet-iodine complex so that the dye cannot be removed
Turns both gram-positive and gram-negative cells from purple to blue-purple
Ethanol (Gram Stain)
The third step in the gram stain method
Acts as a solvent which causes the crystal violet-iodine complex to dissolve away and rinse out of the cell wall if the cells are gram negative
Ethanol does not wash away the iodide and the cell stays blue-purple and gram-negative cells are washed and loses its blue-purple stain
Safranin (Gram Stain)
The fourth step in the gram stain method
Used as a counter-stain that directly stains the bacteria that has been decolorized.
Has not effect on gram-positive cells but turns gram-negative cells orange-red
Koch’s postulates
Set of experimental results that will convince the scientific community that a given microorganism is the main cause of a disease.
The microorganism is both NECESSARY and SUFFICIENT
to cause the disease
- “The same microorganisms are always present in every case of the disease.”
- “The microorganisms are isolated from the tissues of the ‘diseased lesion’ and are grown in pure culture.“
- “Microorganisms from the pure culture, if inoculated into a healthy animal, reproduce the disease.”
- “Identical microorganisms are isolated from the new ‘diseased lesion.’”
Created this through is anthrax research
Maggot
Used in Francesco Redi’s experiments to disprove spontaneous generation
Maggots appeared on the meat that was uncovered
Magnification (microscopy)
Total magnification = Ocular x Objective
A key aspect of microscopes
Miasma (Miasmatic Theory)
Theory that specific bad smells or “corrupt air” can cause disease.
Once microorganisms were linked to disease, miasmatic theory suggested that corrupt air could create microorganisms.
Spallanzani improves Needham’s experiment by boiling the broth after the tubes were capped; leading to the possible disproving of Miasmatic Theory
Still held true for London residents because they didn’t want to believe John Snow
