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14 Cards in this Set

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What is the Streak plate method?
A small droplet or sample is spread over the surface of the medium according to a pattern that gradually thins out the sample, and separates the cells spatially over several sections of the plate.
What is the Loop dilution method/
In this technique, the sample is inoculated serially into a series of cooled but still liquid agar tubes so as to dilute the number of cells in each successive tube in the series.
In an attempt to grow and observe bacteria, what are the 5 I's.
How many types of media are employed?
App. 500 different types of media are used in culturing and identification.
What is liquid media?
They are defined as water based solutions that do not solidify at temperatures above freezing, and they tend to flow freely when the container is tilted.
What is methylene blue milk and litmus milk?
They are opaque liquids containing whole milk and dyes. Fluid thioglycollate is a slightly viscous broth used for determining patterns of growth in O2.
What are semisolid media used for?
They are used to determine the motility of bacteria and to localize a reaction at a specific site.
What is agar?
It is a complex polysaccharide isolated from the red alga Gelidium. It is solid at room temperature, and melts at boiling temperatures. Any medium having 1-5% agar usually has the word agar in its name.
Regarding chemical content of media, what substances may be found in it?
Most substances are extracts of animals, plants or yeast, including ground up cells, tissues and secretions. Examples are blood, serum and meat extracts or infusions. Other nonsynthetic agents are milk, yeast, extract, soybean digests and peptone. peptone is a partially digested protein rich in amino acids, that is often used as a carbon and nitrogen source.
What is an enriched medium?
It contains complex organic substances such as blood serum, hemoglobin or special growth factors(vitamins, amino acids) that certai species must have in order to grow. Those bacteria that require growth factors and complex nutrients are termed "fastidious". Neisseria, cause of gonorrhea, are grown on Thayer martin medium or chocolate agar, which is made by heating blood agar.
What is a selective medium?
It has 1 or more agents that inhibit the growth of a certain microbeor microbes, and encourage or selects one particular microbe and allows it to grow.
Give an example of selective media.
Mannitol salt agar has a high concentration of NaCl(7.5%) that is quite inhibitory to most human pathogens. One exception is the genus, Staphylococcus, which grows well in this medium. Bile salts inhibit most G+ bacteria, while permitting many G neg bacteria to grow.
What is differential media?
This can grow several types of bacteria, but are designed to display visible differences among those micro-organisms. variations in colony size and color, or formation of gas bubbles and precipitates.
Can dyes be used as differential agents?
Yes. Mackonkey agar contains neutral red, a dye that is yellow when neutral and pink or red when acidic. E. coli gives off acid when it metabolizes the lactose in the medium develops red to pink colonies, and salmonella, that does not give off acid remains its natural color(off-white).