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176 Cards in this Set
- Front
- Back
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Whic type of microscope is commonly used to view living cells as it converts slight differences in refractive index and cell density into easily detected variations in light intesnity?
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Compound Microscope
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What is Magnification?
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Magnification is the process of enlarging the size of an object as an optical image.
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How do you determine total magnification?
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Total Magnification: the product of the magnifying power of the ofulars and the objectives
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What is Resolution?
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Resolution is the ability to distinguish objects that are close together. (i.e. clarity).
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What two factors affect resolution?
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The numerical aperature and the wavelength of light used are the factors that affect microscope resoultion.
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How do the numerical aperature and wavelength of light affect the working distance?
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Working distance has to be very close to be affective.
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How does the immersion oil affect the resolution?
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Oil immersion has the same affect as increasing the objective diamter. Oil has the same infractive index as glass, thus closing the working distance.
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If the field of view is 2000 um at 100x, what is the field of view at 400x? at 1000x?
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10x(10x)=100x
2000/1 = 2000 um 40x(10x) = 400x 2000/4 = 500 um 100x(10x) = 1000x 2000/10 = 200 um |
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What is a basic stain also known as?
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Direct, cationic, or positive
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What is a acidic stain also known as?
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indirect, anionic, or negative
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What is simple staining?
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In simple staining, a single dye is used and all organisms take on the same color when stained with this dye. Simple stain can either be acidic or basic.
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What are simple stains generally used for?
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To determine bacterial arrangment and shape.
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What are the bacterial shapes?
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Spheres (coccus)
Rods (baccili) |
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What are the bacterial arrangements?
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strepto - chain
staphylo - irregular cluster diplo - two cells tetrad - four cells sarcina - 8 cells together |
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What is gram staining in terms of differential staining?
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The Gram stain is a differential stain that differentiates bacteria on the basis of their cell wall structure, based on the ability of the bacteria cell wall to retain the crystal violet dye during solvent treatment (Xu, Manual). By using appropriate dyes, different components and structures of the bacteria and the bacteria itself may be made easier to visualize.
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How do differential stains differ from simple stains?
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Simple stains help to stain the outlines of bacterial cells, giving one the characteristic shape, size, and arrangments of the cells stained with the simple stain. For example, you can stain different strains of bacterial cells so that you can better visualise their overall form, size, and arrangments. However, applying a simple stain to a bacterial colony comprising of both types; cells with thick peptidoglycan layer, and cells with thin peptidoglucan layer (as an example), will not help distinguish them, and they tend to look roughly the same given that they're both of the same strain.
Where a differentail stain will differentiate between the two cells. - the differential stain requires the use of multiple stains, the use of lodine and decolorizer such as; acid-alcohol or acetone alcohol and requires heat fixing. |
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What does a G+ (gram positive) cell wall look like?
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The G+ cells appear purple in color in a Gram Stain.
Gram-positive cell walls have a thick peptidoglycan layer beyond the plasma membrane. Characteristic polymers called teichoic and lipoteichoic acids stick out above the peptidoglycan and it is because of their negative charge that the cell wall is overall negative. These acids are also very important in the body’s ability to recognize foreign bacteria. Gram-positive cell walls stain blue/purple with the Gram stain. |
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What does a G- (gram negative) cell wall look like?
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The G- cells appear pink in color in a Gram Stain.
Gram-negative cell walls are more complex. They have a thin peptidoglycan layer and an outer membrane (lipopolysaccharide) beyond the plasma membrane. The space between the plasma membrane and the outer membrane is called the periplasm. The outer leaflet of the outer membrane is composed mainly of a molecule called lipopolysaccharide (LPS). LPS is an endotoxin that is important in triggering the body’s immune response. Gram-negative cells will stain pink with the Gram stain. |
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What is a Microscope?
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Microscope: a device for magnifying objects that are too small to be seen with the naked eye.
Simple microscope: single lens magnifier Compound microscope: employs two or more lenses |
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What is Parfocal?
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Parfocal: the objective lenses are mounted on the microscope so that they can be interchanged without having to appreciably vary the focus.
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What is resolving power or resolution?
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Resolving power or resolution: the ability to distinguish objects that are close together. The better the resolving power of the microscope, the closer together two objects can be and still be seen as separate.
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What is magnification?
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Magnification: the process of enlarging the size of an object, as an optical image
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What is total magnification?
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Total magnification: In a compound microscope the total magnification is the product of the objective and ocular lenses (see figure below). The magnification of the ocular lenses on your scope is 10X.
Objective lens X Ocular lens = Total magnification For example: low power: (10X)(10X) = 100X high dry: (40X)(10X) = 400X oil immersion: (100X)(10X) = 1000X |
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What is the refractive index?
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The refractive index is a measure of the relative velocity at which light passes through a material. When light rays pass through the two materials (specimen and medium) that have different refractive indices, the rays change direction from a straight path by bending (refracting) at the boundary between the specimen and the medium. Thus, this increases the image’s contrast between the specimen and the medium.
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What are two ways to change the refractive index?
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One way to change the refractive index is by staining the specimen. Another is to use immersion oil. While we want light to refract differently between the specimen and the medium, we do not want to lose any light rays, as this would decrease the resolution of the image. By placing immersion oil between the glass slide and the oil immersion lens (100X), the light rays at the highest magnification can be retained. Immersion oil has the same refractive index as glass so the oil becomes part of the optics of the microscope. Without the oil the light rays are refracted as they enter the air between the slide and the lens and the objective lens would have to be increased in diameter in order to capture them. Using oil has the same effect as increasing the objective diameter therefore improving the resolving power of the lens.
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How will a basic simple stain look like under the microscope?
An acidic simple stain? |
Basic, or direct stains will stain the organism.
Negative, or indirect will stain the background. |
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What is heat fixation?
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Heat Fixation: application of heat to a bacterial smear preparation. This procedure simultaneously kills and attaches the bacteria to the slide.
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Which staining technique is the most important? Why?
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Gram stain, as most bacteria can be divided into two groups based on the composition of their cell wall: Gram+ and Gram-
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What are the steps involved in making a Gram stain?
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Come In And Stain
see lab 3 Primary stain: Crystal Violet Mordant: Iodine Decolorizer: Alcohol Counterstain: Safranin |
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How will a G+ cell appear?
G- ? |
G+ = purple
G- = red/pink 1. Gram-positive cells are bacteria that retain the crystal violet-iodine complex, and appear blue/purple under a light microscope. 2. Gram-negative cells are bacteria which are not stained by the crystal-violet iodine complex, and appear red/pink under a light microscope. (Xu, Manual) |
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During Gram staining, which step is most prone to error?
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Overexposure in the decolorization step using ethanol alcohol.
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What do acid-fast cells generally contain a great deal of?
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Mycolic acid, a waxy hydroxylipid that resists staining.
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What is acid-fast staining?
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Acid-fast staining is used to detect cells capable of tertaining a primary stain when treated with an acid alochol (these cells are termed acid-fast.)
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Under a microscope, how does an acid-fast cell look like? Nonacid-fast?
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Acid-fast: red
Non: blue Pink rods = Acid-fast Blue cocci = nonacid-fast The acid-fast Mycobacterium retains carbol fuchsin and stains hot pink. The Staphylococcus epidermidis is decolorized and the counterstain colors them blue. Mycobacterium and many Nocardia species are called acid-fast because during an acid-fast staining procedure they retain the primary dye carbol fuchsin despite decolorization with the powerful solvent acid-alcohol. Nearly all other genera of bacteria are nonacid-fast. The acid-fast genera have lipoidal mycolic acid in their cell walls. It is assumed that mycolic acid prevents acid-alcohol from decolorizing protoplasm. The acid-fast stain is a differential stain. |
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Acid-fast is an important technique in identifying which genus of bacteria?
Which specific pathogens? |
Mycobacterium.
Mycobacterium leprae Mycobacterium tuberculosis |
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Which specific pathogens does the Acid-fast technique identify?
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Mycobacterium leprae
Mycobacterium tuberculosis |
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What is an endospore?
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n endospore is a dense, multilayered structure that contains the genetic material of the bacterial cell.
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Why are endospores formed?
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Endospores are formed within a vegetative bacterial cell when the environmental conditions no longer support cell growth
As the vegetative cell dies, the endospore is released into the environment where it can survive indefinitely in the presence of many environmental stresses, such as dessication, extremes in temperature, radiation, and lack of nutrients. When more favorable conditions arise the endospore germinates back into a viable vegetative cell. |
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Bacteria of several genera form endospores. Name two.
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Bacillus and Clostridium.
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What are some of the pathogenic species of Clostridium?
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Botulism and Tetanus
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How are the presence of endospores detected? Describe the steps of performing an endospore stain.
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Note: Formation of an endospore. The spore stains green and the vegetative cells stain red to orange.
The presence of endospores in a bacterial culture can be detected by staining with malachite green. Because the endospore coat is so tough, the malachite green dye is steamed into cells/endospores. After washing, only the endospores will retain the primary stain Malachite green. Safranin is then used as a counterstain for vegetative cells. The endospore stain is a differential stain because it differentiates spore-formers from non spore-formers. |
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Describe the endospore structure?
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Exosporium - A thin delicate covering made of protein.
Spore coats - Composed of layers of spore specific proteins. Cortex - Composed of loosely linked peptidoglycan and contains dipicolinic acid (DPA), which is particular to all bacterial endospores. The DPA cross links with calcium ions embedded in the spore coat. This cross linkage greatly contributes to the extreme resistance capabilities of the endospores because it creates a highly impenetrable barrier. The calcium DPA cross linkages compose 10% of the dry weight of the endospores. "Calcium Endospore Cross Linkages Confer Resistance" (4) Core - The core contains the usual cell wall and, cytoplasmic membrane, nucleoid, and cytoplasm. The core only has 10-30% of the water content of vegetative cells; therefore the core cytoplasm is in a gel state. The low water content contributes to the endospores success in dry environments. However, the low water concentration and gel cytoplasm contributes to the inactivity of cytoplasmic enzymes. The core cytoplasm is also one unit lower in pH than the vegetative cell, thus conferring acidic environment survival. SASPs, small acid soluble spore proteins, are formed during sporulation and bind to DNA in the core. SASPs protect the DNA from UV light, desiccation, and dry heat. SASPs also serve as a carbon energy source during germination, the process of converting a spore back to a vegetative cell. |
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What two things must occur before the spore will develop into a viable cell?
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Favorable conditions and activation
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What are the steps in spore formation?
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Germentation of Vegetative cell
Sporulation Maturation of spore Activation |
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How is the malachite green driven into the endospore?
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via Steam heating
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Why is the counterstain necessary in the endospore staining procedure?
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To differentiate between endospore forming and non-endospore forming bacteria.
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What are bacterial capsules composed of?
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Many bacteria are surrounded by a slimy layer called a capsule that usually consists of a highly hydrated layer of polysaccharide or in a few cases polypeptide
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What are the functions of a capsule?
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1. helps bacteria escape phagocytic white blood cells,
protects against bacteriophage infection, 2. from dehydration, 3. facilitates the adherence of bacteria to surfaces in certain environments. |
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Why do capsules not require heat fixing to the slide?
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exposure to heat destroys the capsule.
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What do capsule stains look like?
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Cells with capsules appear to have a "halo" around them.
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Define Photoautotrophs
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Energy Source: Light
Carbon Source: CO2 Examples: green and purple sulfur bacteria, algae, and green plants |
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Define photoheterotrophs
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Energy Source: Light
Carbon Source: CO2 Examples: green and purple non-sulfur bacteria |
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Define chemoautotrophs (chemolithoautotrophs)
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The prefix 'lith-' is a Greek root syllable that means 'stone'
Energy source: inorganic chemicals Carbon source: CO2 examples: Thiobacillus (S), Nitrobacter (NO2-1), and Nitrosomonas (NH3) |
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Define Chemoheterotrophs
(Chemoorganoheterotrophs) |
Energy source: Organic source e.g. glucose
Carbon source: organic compounds examples: Most bacteria, all fungi, humans and other animals. |
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Greek/Latin meanins of
lith, troph, hetero, auto, photo |
lith - stone
photo - light troph- feed, grow hetero -different, other auto - self; directed from within |
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Acronym CHNOPS
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Carbon
Hydrogen Nitrogen Oxygen Potassium Sulfur |
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What is a defined medium?
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A Defined medium is a relatively simple medium that is made up of specific chemicals at known concentrations.
A defined medium is often used to determine an organims exact growth requirements i.e. GSA |
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What is an undefined medium?
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i.e. TSA
An Undefined medium is composed of mixtures of yeast cell extracts or enzymatic digests of protein (complex natural extracts and digests of plants, yeasts and beef); the exact amount and kinds of nutrients present in the medium are not known. An Undefined medium tends to support the growth of bacteria better than a defined medium because it contains more preformed nutrients/growth factors (amino acids, nucleotides, and vitamins). Consequently, organisms do not have to expend valuable energy and materials to synthesize the "preformed" compounds supplied in the undefined medium |
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What is a selective medium?
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Selective media contain at least one ingredient that inhibits the growth of unwanted organisms, but permits growth of the desired bacteria. Therefore, these types of media allow for the isolation of a certain bacteria even if they constitute a small percentage of the population in a sample
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What is a differential medium?
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Differential media are formulated to distinguish different microorganisms growing in the medium. These media usually contain a chemical that is utilized or altered by some organisms but not by others. By observing the appearance of the medium or colonies growing on differential media one can identify different organisms exhibiting different physiological traits.
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What is an example of a selective medium?
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EMB
EMB selects for the growth of a gram-negative bactera by suppressing the growth of gram-positive. |
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What are the selective ingredients in EMB?
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Eosin Y and Methylene Blue dyes
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Practice: Two bacteria, one labeled A and the other labeled B, are streaked on an EMB Plate. The bacterium labeled A grows well whereas the bacterium labeled B does not grow at all. Which one, A or B, is Gram-positive?
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B.
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What is an example of a differential medium?
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EMB
Differentiates between bacteria that can ferment lactose (color is purple and oftern has a metallic sheen) with those that cannot. |
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What two types of bacteria does an EMB plate select and differentiate?
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G-
Lactose fermenting. |
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How does a lactose fermenting bactera on an EMB plate look like?
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E. coli - note metallic sheen = lactose fermentor
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What is a GSA?
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Glucose Salts Agar (GSA): is a simple, defined medium. Only organisms that can make all their cellular components from glucose and inorganic salts are able to grow on this medium.
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What is a TSA?
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Tryptic Soy Agar (TSA): is a rich, undefined medium containing products of an enzymatic digest of protein and soy product. Organisms that require vitamins or other growth factors are able to grow on TSA.
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What is an EMB?
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Eosin Methylene Blue (EMB) Agar: is a selective AND a differential medium. The selective components are the eosin and methylene blue dyes that inhibit the growth of Gram-positive bacteria and permit the growth of Gram-negative enteric rods. The differential component of the medium is lactose, which is a sugar that some organisms can ferment as an energy source. Organisms that ferment lactose produce dark purple (sometimes shiny) colonies and those that cannot, produce white or very light pink colonies.
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Quantitation of bacteria can be either direct or indirect. Give examples of both.
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Indirect:
Spectrophotometer – The more concentrated a liquid culture, the more turbid that culture and the more light that it scatters. A spectrophotometer can be used to measure the light scattering/turbidity (generally termed the Optical Density (OD)) of a culture and that can be equated with the number of cells per milliliter. This is a very rapid way to estimate culture titer. Most frequently the OD is measured at 600 nm and is termed the OD600. A concentration (bacteria/mL) versus OD600 curve is then used to estimate the titer. Measurement of the dry weight of the bacterial cells Measurement of metabolic products produced by the bacterial cells Direct Microscopic counts – A set volume of a liquid culture is placed onto a microscope slide and one actually counts the number of cells. The advantage of this method is that no incubation time is required to obtain results. However, it can take a great deal of time to count that many cells and there is no way to distinguish between living and dead cells. MPN (Most Probable Number) – This is a statistical estimation that will be discussed in greater detail later in the semester. Standard Plate Count (SPC) – In this method, a liquid culture undergoes a series of dilutions. Set aliquots of the final, dilute solution are spread onto an agar plate and the plates are incubated overnight. Every cell that was spread onto the plate develops into a visible colony. These colonies can be counted and since they originated from a single cell they represent the number of cells in the final aliquot that was spread onto the plate. The dilutions made from the original culture can then be taken into account and one can work backwards to determine the concentration (titer) of the original culture. |
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What three methods are generally used to derive pure cultures?
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Spread plate – the original culture is diluted serially and a small volume of the final dilution is spread on the surface of an agar plate.
Pour plate –the original culture is diluted serially and a small volume of the final dilution is added to molten agar which is poured over an agar plate and allowed to harden. Colonies develop sub-surface. Streak plate – the original culture is directly diluted across an agar surface using and inoculating loop. This is a simple & rapid method. |
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What is a pure culture?
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A pure culture is a culture that is derived from 1 bacterial cell, so it contains only 1 species.
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True or False. The damage caused by temperatures above the maximum cardinal temperature range is irreversible.
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True.
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Define Pyschrophiles.
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cold-loving organisms, optimum growth temperature is 15°C or lower. These extremophiles are found in the Arctic, Antarctic and lakes fed by glaciers.
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Define Psychrotrophs.
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Psychrotrophs: these species have an optimum growth temperature between 20 and 30ºC but can grow at 0 to 7º C. These play a major role in spoilage of refrigerated foods
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Define Mesophiles.
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mesophiles: include most bacteria, optimum growth temperature is 20 - 45°C. Many pathogens are mesophiles as their preferred temperature is body temperature (37ºC).
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Define Thermophiles.
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thermophiles: heat-loving organisms, optimum growth temperature is 55-65°C. Thermophiles can be found in hot springs, compost heaps, and hot water heaters.
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Define Hyperthermophiles.
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hyperthermophiles: love extreme heat, optimum growth temperature is 70-110°C. Members of this group are generally Archaea.
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Which extremophiles have a optimum growth temperature of 15 C or lower?
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Pyschrophiles
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Which species have an optimum growth temperature between 20 and 30ºC but can grow at 0 to 7º C?
These play a major role in spoilage of refrigerated foods |
Psychrotrophs.
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Which species include most bacteria, optimum growth temperature is 20 - 45°C?
Many pathogens are this, as their preferred temperature is body temperature (37ºC) |
Mesophiles.
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Which species are heat-loving organisms, optimum growth temperature is 55-65°C?
Can be found in hot springs, compost heaps, and hot water heaters. |
Thermophiles.
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Which specieslove extreme heat, optimum growth temperature is 70-110°C?
Members of this group are generally Archaea. |
Hyperthermophiles.
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The rate of growth or death of a particular microbial species is influenced by which physical factors in its environment?
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temperature, osmotic pressure, pH, and oxygen concentration.
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Define acidophiles
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acidophiles: acid-loving organisms, grow best at a pH of 0.1 to 5.5. Most fungi and algae like a slightly acidic environment. Some procaryotic members of Archaea can grow at a pH of 0.
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Define neutrophiles.
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neutrophiles: organisms that grow optimally at pH 5.5 to 8.0. Most bacteria and protozoa are neutrophiles.
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Define alkalophiles.
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alkalophiles: base-loving organisms, grow best at a pH of 8.5 to 11.5.
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What is the optimal pH range of neutrophiles?
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5.5-8
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Define plasmoylsis.
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Playsmoylsis occurs when microorganisms are placed into a hypertonic environment where the concentration of solute is higher outside the cell, water is lost from the cell resulting in dehydration, shrinkage of the plasma membrane and eventual death.
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Define Osmotolerant prokaryotes.
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prokaryotes can maintain the availability of water in environments with high solute concentrations (hypertonic environments) by increasing the solute concentration within the cell. Microorganisms that can do this and thus tolerate hypertonic environments are osmotolerant.
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Define Halophiles
Remember: Latin: Halo - from the sea, or salt |
Some bacteria specifically require an environment with a high concentration of sodium chloride. These organisms are called halophiles.
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Define Aerobes.
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Aerobe - Bacillus subtilis
aerobes: organisms that require atmospheric O2 for growth. |
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Define anaerobes:
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Anaerobe - Clostridium sordellii
anaerobes: organism that are killed or inhibited by the presence of atmospheric O2. |
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Define facultative anaerobes:
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facultative anaerobe - E. coli
facultative anaerobes: organisms that do not require O2 for growth, but do grow better when it is present. |
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Define microaerophiles:
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Microaerophile - Campylobacter jejuni
microaerophiles: organisms that require low concentrations of O2, generally between 2 and 10%. |
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Define aerotolerant anaerobes:
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aerotolerant anaerobes: anaerobic organisms that can survive in the presence of O2, but do not use it in their metabolism.
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What is the biochemistry of the bioluminescence in Vibrio fischeri?
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Overall Reaction: luciferase
RCHO +FMNH2 + O2 --------------------> RCOOH + FMN + H2O + hu RCHO = reduced fatty acid RCOOH = fatty acid hu = light The components required in the reaction are FMN (flavin mononucleotide), oxygen, a reduced fatty acid, and an electron donor, NADH. The reaction is catalyzed by an enzyme complex, luciferase. (Luciferase derives its name from Lucifer, which means "morning star"). The luciferase reaction responsible for bioluminescence is shown below. Molecular oxygen is consumed in the reaction, reminiscent of part of an electron transport system in aerobic respiration, except that instead of serving as the final electron acceptor, oxygen interacts with the enzyme luciferase and FMNH2 to generate light. The importance of oxygen in the luminescence reaction is visibly demonstrated by using a culture of V. fischeri, which has been grown in broth culture without shaking and has thus depleted the medium of oxygen. This culture is turbid, but in the dark it exhibits no luminescence. If the culture is stirred very quickly, allowing the air to pass through it, the culture suddenly starts to glow. |
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What benefits do the V. fisheri get from the symbiotic relationship with the squid?
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V. fischeri benefits by receiving amino acids and possibly other organic carbon and energy sources from the squid. The bacterial cells grow and divide rapidly until the cell density reaches approximately 1011 cells/mL. It is only at this concentration and with the presence of molecular oxygen (presumably provided by the squid) that luminescence occurs
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At what concentration will the V. fischeri bioluminsece?
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1011 cells/mL
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Describe quorum sensing process
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Quorum sensing is a system of signaling correlated to population density. Many species of bacteria use quorum sensing to coordinate gene expression according to the density of their local population
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Define Thymine Dimers
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Thymine dimers are two adjacent thymine bases that are abnormally linked together by covalent bonds caused by UV radiation. This dimerization inhibits DNA replication, which may lead to death of the organism.
UV light has a short wavelength (~10 to 400 nm). UV has a lethal effect on most organisms primarily because of its ability to cause the formation of thymine dimers in DNA. |
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What are the two primary mechanisms generally used for repair of UV damaged DNA?
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Photoreactivation (light repair):
Excision repair (dark reactivation): |
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Define Excision repair (dark reactivation)
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Repair by enzymes > cuts damaged DNA > replaces via DNA polyermase > DNA ligase seals new DNA
http://www.uwyo.edu/virtual_edge/lab08/uv_theory.htm This repair process involves several enzymes: a) An endonuclease called UvrABC1 breaks the sugar phosphate backbone of the DNA strand near the dimer on each side. b) The H-bonds between the base pairs are broken and a segment of DNA ~12 nucleotides long is excised. c) DNA polymerase recognizes the 3’OH primer and fills in the missing bases. d) DNA ligase seals the final sugar-phosphate bond to repair the nicks. |
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Define Photoreactivation (light repair)
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Photoreactivation (light repair): The photoreactivation repair enzyme (PRE) is activated by visible light (400-750 nm).
PRE uses blue light to break covalent bonds between thymine bases, allowing the hydrogen bonds to naturally reform. |
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Define Antibiotics
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Antibiotic: a substance produced by one living organism that kills or inhibits the growth of another organism.
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Define Bactericide
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Bactericide: a substance that kills bacteria.
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Define Bacteriostatic:
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Bacteriostatic: a substance that inhibits the growth and reproduction of bacteria.
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Define Antimicrobic
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Antimicrobic: any agent that kills or inhibits the growth of microorganisms.
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Antibiotic: Pencillin
What is this antibiotic used to often treat? What is its target? |
Gram-positive bacteria.
Targets Bacterial cell wall |
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Antibiotic: Streptomycin, tetracycline, erythromycin, gentamicin
What is this antibiotic used to often treat? What is its target/mechanism? |
Broad bacteria range.
*broad spectrum drug Mechanism: inhibits protein synthesis by binding to the bacterial 70S ribosome to prevent protein synthesis |
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Antibiotic: Nystatin and polymyxin
What is this antibiotic used to often treat? What is its target? |
polymyxin-gram-negative bactera
nystatin-fungal infections Targets bacterial cell membrane |
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Antibiotic: naladixic acid
What is this antibiotic used to often treat? What is its target? |
broad bacteria range
*broad spectrum drug Mechanism: affect DNA or RNA synthesis |
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Antibiotic: sulfa drugs
What is this antibiotic used to often treat? What is its target? |
Broad bacteria range.
*broad spectrum drug Mechanism: Antimetabolite |
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Define Selective Toxicity
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Selective toxicity is the ability of a substane to kill one specific organism but not another.
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Define Disinfectants
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Disinfectants are chemicals that are used to kill, inhibit or remove microorganisms residing on inanimate objects such as lab benches, bathtubs, kitchen floors etc. Lysol and 409 are examples of disinfectants.
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Define Antiseptics
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Antiseptics are chemicals that are applied to body surfaces in an attempt to prevent/control infection. Iodine and Listerine are two examples
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Define Sterilization
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Sterilization is the removal of all living cells including spores and viroids
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Define Sanitization
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Sanitization means to reduce the microbiual population to levels considered safe by publich health standards
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What are the mechanisms of phenolic compounds, detergents, and alcohols?
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Phenolic compounds and detergents disrupt microbial membranes and denature proteins.
Alcohols denature proteins also, and they actually extract membrane lipids. |
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What are the mechanims of halogens and hydrogen peroxide?
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The halogens and hydogren peroxide oxidatively damage cell consitituents.
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What are the three mechanisms of bacterial recombinations?
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Transformation, transduction, and conjugation.
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Define Transformation.
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Transformation is a genetic exchange mechanism by which “naked” DNA is taken up by bacteria.
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Define Transduction.
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Transduction is the process by which DNA is transferred from one bacterium to another by a virus.
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Define Conjugation
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Bacterial conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells. i.e. plasmids
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Describe the process of the transformation of E. coli with pGLO and how we can test for this.
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The pGLO plasmid also contains a gene encoding for beta-lactamase. Beta-lactamase is an enzyme that will allow transformed bacteria to be resistant to antibiotics that have a beta-lactam ring. Thus, in order to identify bacteria that have been transformed with pGLO, we select for their growth using a media that contains an antibiotic with a beta-lactam ring, ampicillin. The use of media containing ampicillin allows for the selection of successful transformants, however it is only when the sugar arabinose is also added to the media that it will be possible to observe the bright green fluorescence. This is because the GFP protein is under the control of an arabinose operon. Thus, arabinose acts like a switch turning on the section of DNA that codes for GFP.
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Define Bacteriophages
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Bacteriophages are viruses that infect bacteria, using a bacterium as its host cell.
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What are the 5 steps of the bacteriophage replication cycle?
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All People Buy Moldy Lemons
The lytic cycle of virulent phage consists of 5 sequential stages: Adsorption – A phage attaches to specific receptor sites on the surface of the host cell. This receptor conforms to molecules present on the phage tail. A phage cannot attack bacteria that do not have receptor molecules that conform to the phage tail proteins. Penetration – The phage tail fibers contract and the baseplate settles down on the cell surface. The phage forms a hole in the cell wall using phage lysozyme, an enzyme, and drives the tail core through the cell wall and membrane. The phage DNA is then injected into the bacterial cytoplasm. The head (capsid) and tail stay outside and are referred to as the phage ghost. Biosynthesis - Once inside the cell, phage DNA redirects host cell metabolism. It subverts the cell machinery to the exclusive manufacture of nucleic acid and protein molecules needed for the assembly of hundreds of new phage. For several minutes following infection, complete phage cannot be found; this is called the eclipse period. Maturation - Phage DNA, head protein and tail proteins are synthesized separately and then assembled during this step. The head protein is packaged with phage DNA and then the tail is attached. The eclipse period is over when the first complete phage appears in the cell. Lysis - Lysozyme coded for by the phage DNA causes the host cell to burst releasing intact phages to infect neighboring cells. For some phage, the cycle may be completed in as quickly as 15 minutes. |
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What are the two types of bacteriophages?
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Virulent
Temperate |
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Define Virulent
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Virulent bacteriophages (e.g., T4) multiply rapidly after infecting a host cell and destroy the cell through lysis
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Define Temperate
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Temperate bacteriophages integrates into the host cell's DNA = a prophage (the host cells are called lysogenic bacteria), can later take the lytic pathway
Temperate bacteriophages (e.g., lambda) may lyse the host cell or lysogenize the host. If lysogeny occurs the phages produce a protein, called a repressor that prevents replication of the phage DNA. Instead the phage DNA integrates into the host genome where it is referred to as a prophage. When the bacterial host DNA replicates, the prophage DNA is replicated as well. Thus, all bacterial daughter cells carry a copy of the prophage DNA and are referred to as lysogenic bacteria. The lysogenic cells may exhibit new properties such as toxin production (e.g., scarlet fever, diphtheria or botulism). |
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True or False. Bacteriophages are very small and thus can pass through a filter with pores small enough to exclude bacteria.
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True.
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Define plaque.
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A plaque is a clear zone in the bacterial lawn where a phage has infected and lysed the bacteria.
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What are Fungi?
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Fungi are eukoaryotic chemorganoheterotrophs that secure nutrients mostly from decarying organic material (saprophytes).
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Define Saprophytes
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sapro- Greek rotten, putrid
phyte - plant saprophytes; the organic matter from which fungi take their nutrients is dead |
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True or False. Fungi include both yeasts and molds.
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True
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Define Yeasts.
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Yeasts are typically spherical or oval in shape and are widely distributed in nature (found on fruits, leaves of trees, etc). Yeasts reproduce asexually by budding, a process by which a new cell forms as a protuberance (bud) from the parent cell.
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Define Molds.
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Molds come in many sizes, shapes, and forms, ranging from mushrooms, puffballs and large bracket fungi found on trees to the small colonies often found as contaminants on moldy fruits and cheeses.
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What are the two types of Hyphae?
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Coenocytic hyphae
Septate hyphae |
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What does a Coenocytic hyphae look like?
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What does a septate hyphae look like?
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Hypahe form a tangled web called a _________.
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mycelium
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Mycelium
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Hyphae intertwine to form mycelium
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Do yeast reproduce asexually or sexually?
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Asexually via budding.
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True or False. Molds can reproduce sexually or asexually.
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True.
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What are the 6 types of spore reproduction/formation
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When hyphal fragementation occurs, the resulting spores are termed arthrospores.
If the cells are surrounded by a thick wall before hyphal fragmentation, the spores are instead called chlamydospores. Spores that develop within a sac (sporangium) at a hyphal tip are referred to as sporangiospores. If spores are not produced in a sac, but do develop at a hyphal tip or sidewall they are called conidiospores. spores produced from a vegetative cell by budding are blastospores. Sexual reproduction involves the union of two nuclei. Sexual life cycles vary from one fungal species to another. However, most have a diploid stage, which involves the formation of a spore that can survive in harsh external conditions. |
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Draw all types of spore formation
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What are the six subdivisions of fungi?
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Chytridiomycota (chytrids):
The simplest of the fungi, the chytrids are microscopic and found in freshwater, mud, soil and sometimes the rumen. Zygomycota (bread molds): Members of the subdivision Zygomycota have coenocytic hyphae. Asexual reproduction is via sporangiospores, which can be released from the sporangium and carried by air currents. When the spores reach an appropriate substrate, they germinate to produce new hyphae. Bread molds do not usually cause human disease. In fact, in some countries they are used in food production. Rhizopus, however, is an opportunistic human pathogen; it is especially dangerous to people with diabetes mellitus that is not well controlled. Ascomycota (sac fungi): Members of the subdivision Ascomycota include molds that have septate hyphae and some yeasts. They are called sac fungi because their sexual spores, called ascospores, are produced in a sac or ascus. Asexual reproduction is via conidiospores. The Ascomycetes include fungi that cause chestnut blight and Dutch elm disease. Claviceps purpurea is a parasite on rye grass that causes ergot. Basidiomycota (club fungi): Basidiomycetes also possess septate hyphae. The sexual spores, called basidiospores, are produced by a club-shaped structure called a basidium. In mushrooms the basidia are found along the gills or pores on the underside of the cap. Some mushrooms produce toxins that are lethal to humans. Glomeromycota (mycorrhizae) Most are mycorrhizal fungi that form a mutualistic symbiosis with the roots of plants. Microsporidia Obligate intracellular parasites of fish, humans and insects |
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Three subdivisions of fungi most discussed in class:
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Zygomycota (bread molds):
Members of the subdivision Zygomycota have coenocytic hyphae. Asexual reproduction is via sporangiospores, which can be released from the sporangium and carried by air currents. When the spores reach an appropriate substrate, they germinate to produce new hyphae. Bread molds do not usually cause human disease. In fact, in some countries they are used in food production. Rhizopus, however, is an opportunistic human pathogen; it is especially dangerous to people with diabetes mellitus that is not well controlled. Ascomycota (sac fungi): TRUFFELS Members of the subdivision Ascomycota include molds that have septate hyphae and some yeasts. They are called sac fungi because their sexual spores, called ascospores, are produced in a sac or ascus. Asexual reproduction is via conidiospores. The Ascomycetes include fungi that cause chestnut blight and Dutch elm disease. Claviceps purpurea is a parasite on rye grass that causes ergot. Basidiomycota (club fungi): MUSHROOMS Basidiomycetes also possess septate hyphae. The sexual spores, called basidiospores, are produced by a club-shaped structure called a basidium. In mushrooms the basidia are found along the gills or pores on the underside of the cap. Some mushrooms produce toxins that are lethal to humans. |
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Which bacteria are G-?
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Escherichia coli
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Which bacteria are G+?
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Bacillus subtilis
Staphylococcus epidermidis |
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Which bacteria are faculative anaerobes?
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Escherichia coli
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Which bacteria is host of the T4 bacteriophage?
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Escherichia coli
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Which bacteria would show as a lactose fermenter on an EMB plate?
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Escherichia coli
Enterobacter aerogenes |
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Which bactera are halotolerant?
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Saccharomyces cerevisiae
Staphylococcus aureus |
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Which bacteria is yeast?
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Saccharomyces cerevisiae
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Which bacteria is a thermophile?
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Bacillus stearothermophilus
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Which bacteria are acid-fast?
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Mycobacterium smegmatis
Mycobacterium tuberculosis Mycobacterium leprae |
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Which bacteria is an obligate aerobe?
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Bacillus subtilis
Clostridium sordellii |
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Which bacteria are endospore-forming?
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Bacillus Subtilis
Clostridium botulinum Clostridium tetani Clostridium perfringens |
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Which bacteria causes gangrene?
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Clostridium perfringens
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Which bacteria causes tetanus?
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Clostridium tetani
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Which bacteria causes botulism?
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Clostridium botulism
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Which bacteria are capsule-forming?
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Klebsiella pneumoniae (bacillus)
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What bacteria is a micraerophile?
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Campylobacter jejuni
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Which bacteria causes many food poisonings?
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Campylobacter jejuni
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What bacteria is a halophile?
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Halobacterium salinarium
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Which bacteria is a psychrotroph?
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Pseudomonas fluorescens
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What bacteria is a bio luminescent?
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Vibrio Fisheri
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Which bacteria is sensitive to UV radiation?
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Micrococcus luteus
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What are two bacteriophage examples?
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T4 bacteriophage
Lambda phage |
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Give an example of a lysogenic bacteriophage
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T4 bacteriophage
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Give an example of a temperate bacteriophage
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Lambda phage
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Which bacteria are non-fastidious?
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Escherichia coli
Pseudomonas aeruginosa Enterobacter aerogenes |
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List the characteristics of E. Coli
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G-
Faculative Anaerobe Host of T4 bacteriophage bacilli (rod) |
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List the characteristics of Bacillus subtilis
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G+
obligate aerobe endospore-forming bacilli (rod) |
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List the characterisitics of Myobacterium
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acid-fast rods
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