Micb203

Front 1

liquid culture media are used for?

Back 1

growing large numbers of bacteria in a short period of time.

Front 2

semi-solid culture media are used for?

Back 2

motility studies

Front 3

solid slant culture media are used for?

Back 3

store cultures of various periods of time

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solid plate cultures are used for?

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isolate individual bacteria from a sample.

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simple stains

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colour all bacterial cells in a similar way (e.g. methylene blue)

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differential stains

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divide bacteria into separate groups based on staining properties (e..g gram stain)

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phase-contrast microscope

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allows the visualization of cels without staining

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bright field microscopy

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used for the examination of stained cells using a compound light microscope.

Front 9

oil immersion is necessary because

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oil has the same reflective index as the glass slides.

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gram positive cells strain?

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purple

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gran negative cells stain?

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pink

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heat fixing

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kills the organisms and coagulates proteinaceous substances of cells which fastens the organisms to the slide.

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primary stain

Back 13

crystal violet is the primary stain in the gram staining procedure.

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mordant

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Gram's iodine. the crystal violet and gram's iodine will form a complex which increases the interaction of the dye and the cell so the dye binds more tightly to the cell.

Front 15

differentiation step in gram stain

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wash with 95% alcohol will turn gram-negative cells colourless while the gram-positive cells remain purple

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counter stain

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aqueous fuchsin stains gram-negative cells pink

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basic stains

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attracted to the opposite charge and color negatively charged bacterial cells (e.g. crystal violet, methylene blue, and safranin)

Front 18

acidic stains

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repelled by like charge and color the background surrounding negatively charged bacterial cells, so you can see the cells in outline (e.g. congo red, nigrosin, india ink)

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blood agar

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differentiates bacteria on the basis of blood cell hemolysis

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beta-hemolysis

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bacteria completely lyse red blood cells, resulting in a clear area around colonies

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alpha-hemolysis

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bacteria partially lyse red blood cells, resulting in a greenish discoloration around colonies.

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gamma-hemolysis

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bacteria do not lyse red blood cells, so the appearance of the agar remains the same.

Front 23

spectrophotometer

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measures the turbidity of a broth culture for estimating the number of bacteria in a culture.

Front 24

optical density

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the cell concentration is proportional to the amount of light scattered. both living and dead cells are measured.

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standard plate count

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a series of dilutions of a culture is plated. only viable cells are counted.

Front 26

violet red bile agar

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selective and differential medium that selects for coliform organisms, and the presence of coliform organisms may indicate fecal contamination in water or dairy products.

Front 27

why are blanks necessary for spectrophotometer

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coloured molecules absorb light, so a blank solution same as the one cells are suspended in are used to calibrate the spectrophotometer.

Front 28

the samples should be measured in order of ____ for spectrophotometry.

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increasing concentration

Front 29

adsorption

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first step in the bacteriophage infective process. the attachment of a specific phage to a receptor site on the bacterial cell.

Front 30

injection

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insertion of phage nucleic acid into the host bacterial cell

Front 31

4 steps in bacteriophage infective process

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adsorption, injection, replication, and lysed.

Front 32

charged pipette

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bacteriophage adhere to glass, and pipettes must be charged by pipetting the solution up and down a least three times.

Front 33

how are microorganisms identified?

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macroscopic morphology, microscopic morphology, and metabolic tests

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catalase test

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when drops of a diluted solution of H2O2 are added onto bacteria containing catalase, bubbles of O2 rapidly appear. these bubbles indicate the presence of catalase and denote a positive test.

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oxidase

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determines if bacteria have cytochrome oxidase. when cytochrome oxidase adds electrons to the oxidase reagent, the reduced form turns dark blue to purple within seconds.

Front 36

mineral oil

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create an anaerobic atmosphere for API-20E

Front 37

citrate utilization test

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if the bacteria utilize citrate, the byproduct CO2 combines with Na+ in the medium to form NaCO3, turning the pH indicator from green to blue (positive test).

Front 38

DNase Test

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if the bacteria secreted DNase. no large DNA molecules remain around the growth and a clear zone is observed (positive test).

Front 39

bile esculin agar

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bacteria utilize esculin in the presence of bile produce a product that reacts with the ferric citrate in the medium, turning it from yellow to dark brown.

Front 40

fermentation tubes

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heterotrophic bacteria often use sugars in fermentation pathways, producing acids, alcohols, and gases. acid production turns the medium from pink to yellow, and gases are trapped in an inverted tube in the medium

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gelatin hydrolysis test

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some bacteria can hydrolyze gelatin with the extracellular enzyme gelatinase, causing the gel to liquefy.

Front 42

indole

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some bacteria can degrade tryptophan to pyruvate, producing indole as a byproduct. When Kovac's reagent is added, it reacts with indole and form a red layer at the top of the tube.

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MR

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products of mixed-acid fermentation of glucose include significant amounts of organic acids. these acids lower the pH of the medium and when the pH indicator methyl red is added, it remains red in color (positive test). when less acid is present, the color may be orange or yellow (negative).

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motility

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motile cells with flagella swim away from the stab and non-motile bacteria will grow only along the stab.

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nitrate reduction

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if nitrite ions are produced, reagent A and B turns the medium pink or red (positive). in the absence of color change, either the nitrate ions were not reduced to nitrite ions (true negative test), or the nitrate ions were completely reduced to molecular nitrogen. zinc is added to check whether the nitrate ions were completely reduced to molecular nitrogen, which which case no color change is expected (positive).

Front 46

triple sugar iron (TSI)

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if bacteria ferments lactose, sucrose, or glucose, pH decreases and the medium appears yellow. if a bacterium can reduce thiosulfate, ferrous ions in the medium will combine with sulfide ions to form black precipitate.

Front 47

TSI yellow slant yellow butt

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glucose and lactose and/or sucrose were fermented

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TSI red slant and yellow butt

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only glucose was fermented

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TSI red slant and red butt

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none of the sugars were fermented, and not a member of the Enterobacteriaceae

Front 50

TSI cracks or bubbles in yellow agar

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gas was a byproduct of fermentation

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TSI black precipitate in butt

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H2S was produced

Front 52

urea test

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urease producing bacteria converts urea to carbon dioxide and ammonia, which raises the pH and turns media pink.

Front 53

VP

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fermentation of glucose via butanediol fermentation produces acetoin, which reactions with VP reagent in the presence of O2 to form a red product.

Front 54

MacConkey Agar

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crystal violet and bile salts select for gram-negative bacteria. lactose is added to make the medium differential. bacteria that utilize lactose will have pink to red colonies, while non-lactose fermenting bacteria will have colorless colonies.

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DNA can be transferred between prokaryotic organisms in three ways.

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transformation, transduction, and conjugation.

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transformation

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uptake of naked DNA by recipient cells.

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Acinetobacter calcoaceticus

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competent throughout exponential growth and its use obviates the preparation of competent cells.

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wildtype

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strain of bacteria isolated from nature or the usual form of a gene

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auxotroph

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organism that has developed a nutritional requirement through mutation.

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sodium dodecyl sulfate

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solubilizes the outer cell wall

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EDTA

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helps in cell lysis and binds the Mg2+ required by DNA degrading enzymes and thus protecting them.

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ethanol

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precipitates DNA

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sodium acetate

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neutralizes DNA's negative charge, allowing easier precipitation

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Tris HCl

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buffer for redissolving precipitated DNA.

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plasmid DNA separated from chromosomal DNA on the basis of?

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size and conformation (degree of supercoiling)

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alkaline lysis method

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DNA is denatured with NaOH and SDS at alkaline pH.

Front 67

KOAc

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neutralizes NaOH in alkaline lysis. chromosomal DNA, due to its large size, cannot reanneal and becomes trapped in the K/SDS complex. the renatured plasmid remains soluble in the solution and can be found in the supernantent.

Front 68

restriction endonucleases

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enzymes that recognize and cleave double-stranded DNA at specific palindromic nucleotide sequences.

Front 69

agarose gel electrophoresis

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a simple and effective method for separating, identifying, and purifying DNA fragments.

Front 70

the rate of migration through agarose gel is affected by?

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voltage, size, and shape.

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supercoiled

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covalently closed circular, most compact form and will migrate the farthest

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linear

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duplex, migrate somewhat slower then the supercoiled form

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nicked

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relaxed or open circular, migrate the least distance

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RISK Group 1

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Not known to consistently cause disease in healthy individuals

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RISK Group 2

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Associated with human disease hazard i.e. cuts, injury, ingestion exposure

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RISK Group 3

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Indigenous or exotic agents with potential for aerosol transmission, disease may have serious or lethal consequences

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RISK Group 4

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Dangerous/exotic agents which pose high- risk of life-threatening disease , aerosol- transmitted lab infections or related agents with unknown risk of transmission