Studied by 42 peopleWhat are the 7 characteristics of life?
-Homeostasis -Organization -Metabolism* -Growth -Adaptation -Response to stimuli -Reproduction*
If something is alive, then it must _
-be made of one or more cells -have a cell membrane -have a double stranded DNA genome -be prokaryotic or Eukaryotic
Why are viruses not considered living?
They lack a cell membrane, have varying genomes, either double or single stranded, can have RNA or DNA.
Which characteristics of life do viruses poses?
Adaptation and reproduction
Why can RNA based viruses reproduce faster?
They lack the proofreading protections that DNA reproduction has.
Why are prions not considered living?
They lack a cell membrane, Genome, and are ODD--
what is a plasmid?
a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium or protozoan. Plasmids are much used in the laboratory manipulation of genes.
When was the LUCA?
3.9 billion years ago
What are the 3 domains of life?
Bacteria, Archaea, Eukarya
Who created the microscope?
Zacharias Janssen
Who was the first person to observe and describe microorganisms accurately?
Antonie Van Leeuwenhoek
Who is the father of microbiology?
Anton van Leeuwenhoek
Describe Cell theory
All living organisms are composed of one or more cells
Cells are the basic functional units of all living organisms
All cells arise from preexisting cells (biogenesis)
what is the Miasma theory
Diseases are caused by bad air.
what was the theory of spontaneous generation?
Abiogenesis, living organisms can arise spontaneously from non-lving material, eg frogs from mud and maggots from meat.
What did Francesco Redi do?
He had 2 jars both which contained meat. One was covered and the other was uncovered. the uncovered jar had maggots while the covered jar had none.
what did Agostini Bassi do?
showed that a disease of silkworms was caused by a fungus
Germ Theory of Disease
idea that infectious diseases are caused by microorganisms
Describe the Swan neck experiment
-An experiment done by Louis Pasteur in which a nutrient broth is heated in a flask with a swan neck, after one year, the nutrient broth remains free of microorganisms. When the curved neck is removed, the nutrient broth begins to teem with microorganisms
What did Louis Pasteur develop?
Pasteurization- allowed preservation of wine for storage. Demonstrated alcohol fermentations and other fermentations were the result of microbial activity. -Yeast causes fermentation, converts sugars to alcohol in the absence of air.
How did Louis Pasteur overcome the spoilage problem?
He recommended heating alcohol just enough to kill bacteria- pasteurization
Describe HTST pasteurization
milk is heated at 72 degrees Celsius for 15 seconds.
Describe UHT pasteurization
milk is treated at 140 degrees Celsius for 3 seconds then cooled quickly in a vacuum chamber.
What did John Tyndall do?
Demonstrated dust carries microorganisms, proved existence of exceptionally heat-resistant forms of bacteria.
What did Joseph Lister do?
howed microorganisms were causal agents of disease, developed a system of sterile surgery
What did Robert Koch do?
-identified the bacterium that causes tuberculosis -Led to the discovery or development of Agar, the petri dish, nutrient broth and nutrient agar, methods for isolating microorganisms
What is agar isolated from?
Algae
What are Koch's postulates?
1.The organism should be present in all animals suffering from the disease and absent from all healthy animals 2. The organisms must be grown in pure culture outside the diseased animal- anthrax, caused by Bacillus anthracis 3. When the culture is inoculated into a healthy susceptible animal, the animal must develop the symptoms of the disease 4. The organism must be re-isolated from the experimentally infected animal and shown to be the same as the original isolate.
What is Edward Jenner known as?
the father of immunology
Who developed the first attenuated vaccine against chicken cholera in 1880?
Louis Pasteur
When did antibiotic resistant bacteria emerge?
Shortly after Alexander Fleming discovered penicillin
Magnification
makes objects look larger (not limited)
resolution
the ability to see two items as separate and distinct (limited)
Resolving power
the measure of clarity of an object
Refraction
bending of light when it changes medium, eg immersion oil
transmission
light rays pass through an object
fluorescence
the use of UV light... absorb light at one wavelength and emit light at a different wavelength almost instantaneously
Absorption
light rays are taken in by an object and absorbed
The _ the magnification, the _ the NA
higher, higher
the _ magnification, the _ light is needed
more, more
NA (numerical aperture)
AAThe light gathering ability of a lens
resolving power formula
(wavelength of light)/(2x numerical aperture) -the shorter the wavelength, the greater the resolving power
Light microscopy
use of any kind of microscope that uses visible light to observe specimens -Uses photons -low magnification
What are the 5 main subtypes of light microscopy?
-Bright-field -phase contrast -differential interference contrast -Dark-field -Fluorescence
what are the 2 main types of electron microscopy?
Transmission electron (TEM) Scanning electron (SEM)
Electron microscopy
Uses electrons scattered by objects for visualization -high magnification capability
How is resolution affected by wavelengths?
It is limited by this, as this goes down, Frequency increases, power increases, clarity is improved.
How can you improve image quality?
Using contrast or dimensionality
What is one issue that occurs when staining a specimen?
The stain used most likely will kill the specimen
What are ways to improve light to increase contrast?
Use of : -phase contrast -Fluorescent -Dark field microscopy -differential interference -confocal scanning laser microscopy
What is a way to improve the image via dimensionality?
microtome sections
A 2 step Gram procedure is an example of what type of staining?
Differential staining
2 step gram procedure:
flood the heat-fixed smear with crystal violet for 1 min
add iodine solution for 1 minute 3)decolorize with alcohol briefly - 20 seconds 4)counterstain with safranin for 1-2 minutes
What are three types of microscopes?
Visible light Ultraviolet rays electron beam
How does the magnification difference between UV rays, Visible light, and electron beam microscopes?
Visible light and UV ray microscopes have a magnification up to 2000x while electron beam has a magnification range between 5000x - 1,000,000x
How do you calculate for magnification?
Occular * Objective
How does the 2 step gram stain work?
bacteria is negatively charged, adding positively charge die allows the two to bind.
What type of gram charge does gut E.coli have?
gram -
what type of gram charge does skin E.coli have?
gram +
What are lenses?
Curved, transparent surfaces that bend light waves (refraction)
describe bright-field microscopy
-Forms its image when light is transmitted through the specimen -specimens are visualized because of slight differences in contrast that exist between them and their surrounding -can be used with live, unstained, and preserved, stain specimens -most widely used
Describe dark-field microscopy
-Light reaches the specimen from the sides -the only light reaching the lens is scattered by the specimen -does NOT use stain -specimen appears light on a dark background -effective for visualizing living cells that would be distorted by drying or heat that can't be stained with usual methods -does not allow for visualization of fine internal details of cells -the stop blocks all light from entering the objective lens except for peripheral light
How can a bright field microscope be adapted as a dark field microscope
By the addition of a stop to the condenser
Describe phase contrast microscopy
-Used for live specimens, observes motility and response to stimuli -Used to observe unstained/lice cells and thin specimens -specimen is contrasted against a GRAY background -excellent for internal cell details -more expensive than other methods
What type of microscopy would be used to observe a light sensitive organism?
dark field microscopy
how does differential interference contrast microscopy improve depth?
A polarizer is used in the condenser, polarised light splits into 2 out of phase beams, 2 beams of polarized light that are not in phase pass through the object
how does a confocal scanning laser microscope improve depth?
The image is built in stages using the ability to precisely adjust the laser focal phase
What is Differential-interference contrast microscopy useful for?
-Allows detailed view of live, unstained specimens -provides a colorful 3D image (includes 2 prisms that add contrasting colors to the image
What source does a fluorescence microscope use?
UV radiation
Describe fluorescence microscopy
-Ultraviolet light is used to excite electrons in molecules
Most organisms observed in this way must first be treated with a fluorescent dye or fluorochrome. -Forms a colored image against a black field
what is fluorescence microscopy used for?
Diagnosing infections caused by specific bacteria, protozoa, and viruses using fluorescent antibodies
How do electrons avoid refraction?
by traveling in a vacuum
How are electrons able to have increased resolving power compared to visible light waves?
They travel in wavelike patterns 1000x shorter than Vis light
Describe a transmission electron microscope (TEM)
An electron beam passes through the unstained areas of the specimen, focused by electromagnets, and reflects off stained areas lengthy preparation process = specimen undergoes lengthy dehydration process before being embedded in resin produces 2d, black and white images -has up to 100,000x -electromagnets function as lenses -operates in a vacuum -capable of viewing structures of cells and viruses -REQUIRES 20-100 nm thick specimens that also must be stained
what do the dark areas of TEM image represent?
Thicker/denser parts
Describe a Scanning Electron Microscope (SEM)
electron beam bombards the surface of specimen (not through it) ad scans back and forth across it. specimen is coated in a thin layer of gold or platinum before placing in vacuum chamber. -Has up to 650,000x magnification -deflected electrons are picked up by a detector -creates extremely detailed 3-D view of all kinds of objects
Which microscopy type condenses the light source into parallel rays?
Bright-field microscopy
Which microscopy type(s) can contrast samples via staining
Bright-field microscopy and Fluroescence
Which microscopy techniques require unstained cells?
Phase contrast, Differential interference contrast, and Dark-field
What type of source does a fluorescence microscope have?
a UV radiation source
What type of image is formed by a fluorescence microscope?
a colored image against a black field
what type of image results from a DIC microscope?
-detailed views of live unstained species and a colorful three dimensional image.
What size must specimens be for phase-contrast microscopy to be effective?
Thin specimens
What size must specimens be for Dark-field microscopy to be effective?
THICK
What is phase contrast microscopy used for?
-examining live specimens and their motility in response to stimuli -examining internal cell details
What is dark field microscopy most affective for?
visualization of living cells that would be distorted by drying or heat that can't be stained with usual methods.
Does dark field microscopy allow for visualization of fine internal details of cells?
no
Which microscopes can improve the image by improving the light?
Bright-field Phase-contrast Dark-field
Which microscopes improve the image by improving depth?
DIC and confocal scanning laser microscopy
In what way do the stains for TEM and SEM differ?
TEM stains are thick like resin while SEM stains are specialized to repel electrons
What is the usual size of bacteria?
1x2 micrometers
Would a small cell have a larger surface area to volume ratio?
yes
Between red and blue light, which would have a higher resolving power?
blue light because resolving power increases as wavelength decreases
As cell size increases, what happens to the surface area ration?
It decreases
Cell volume impacts what?
Chemical rxn activity, as _ increases, chemical rxn activity increases
cell surface area impacts what?
the rate of exchange
What happens to surface area as cell size increases?
surface area does not increase at the same rate or extent.
As cube size increases, the surface volume ratio __
decreased
What happens when the Surface area to volume ratio decreases?
substances cannot enter the cell fast enough waste cannot be removed fast enough-- accumulation the cell cannot lose heat fast enough --- overheating
What can be achieved by staining specimens?
increased visibility of specimen accentuated morphological features preservation
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