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Because it does not inhibit bacteria form "swimming" through the medium.
Wiki User
∙ 13y ago
Wiki User
∙ 11y agoThe semi-solid media is perfect for growth of cells, specifically bacteria. If the bacteria spreads quickly in the media then it can be deduced that there is sufficient motility.
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What concentration of agar is used in a semisolid medium for motility How does that compare to a typical solid medium?
Agar concentration rates for a semisolid medium for mobility typically ranges from 0.2 to 0.4 percent. Solid medium can have as much as 15 to 20 percent agar.
When testing microaerophils some microbiologists prefer to use a semisolid nitrate medium that contains a small amount of agar why is this done?
Microbiologists testing microaerophils prefer to use a semisolid nitrate medium that contains a small amount of agar to get more accurate results. This is also done to speed up the results.
Microbiology - what is SIM test?
Its a test where a semisolid agar called Sulfide-Indole-Motility medium (or SIM medium) is inoculated with a bacteria to test for hydrogen Sulfide, Indole, and Motility of the organism. The medium is inoculated by a swab and stab type method (rub some bacteria on the surface of the medium and stab a straight hole through the medium using a straight wire with the bacteria on it). Incubate the bacteria for about 24 hours and then begin testing.... If hydrogen sulfide is present, it will react with the sodium thiosulfate in the medium and the indicator, ferric ammonium citrate, to produce ferrous sulfide which falls out of solution as a blackish precipitate. The presence of hydrogen sulfide typically means that the bacteria produces the enzyme cysteine desulfanase which breaks up the cysteine in the medium into, among other components, hydrogen sulfide. The Indole portion of the test is performed by adding Kovac's reagent to the inoculated medium. The Kovac's reagent reacts with the indole(if indole is present) to produce a pinkish-red or redish-purple ring around the top of the test tube. If indole isn't present, there will be no color change. The presence of indole means that the bacteria produces tryptophanase, an enzyme which breaks down tryptophan into smaller components, one of which being indole. The Motility aspect of the test is done by checking the medium for turbidity, or "fuzziness". If the medium has become fairly turbid throughout the medium, then the bacteria is motile. If the medium is clear and the only turbid appearance is in the stab line, then the bacteria is non-motile. Unfortunately, the motility aspect of this test typically gives false negative results. Sometimes the temperature that the bacteria was incubated at wasn't optimum for the species, sometimes the bacteria only have weak motility, sometimes the bacteria's flagella can get damaged which would impair motility, etc... The point is, this test is good if you want to know whether or not the bacteria you're testing produces tryptophanase or cysteine desulfanase. The motility aspect of the test is suspect to question, at least if the test result was negative for motility(a large amount of turbidity in the medium is a definite sign of motility and is hard to refute though).
When testing microaerophiles prefer to use a semisolid nitrate medium that contains small amount of agar Why?
microaerophiles grow below the medium surface of culture, in presence of oxygen required (equal or matched ) by them .
What the other method used to determine motility?
You can do an experiment to determine motility. You use a medium of agar that has tetrazolium salt (TTC). The TTC serves as a terminal electron acceptor for the bacteria and turns the medium red. You would inoculate a needle with your bacteria and put it straight into the media and straight out. After incubating your bacteria, if you see the red move away from where you inserted the needle, then it would indicate that your bacteria is motile. If the red is only in the place where you inserted the needle, then it is not motile.
What concentration of agar is used in a semisolid medium for motility How does that compare to a typical solid medium?
Agar concentration rates for a semisolid medium for mobility typically ranges from 0.2 to 0.4 percent. Solid medium can have as much as 15 to 20 percent agar.
Why are semisolid media sometimes preferred over techniques for evaluating bacterial motility?
Because it does not inhibit bacteria form "swimming" through the medium.
How and why does the agar concentration in semisolid media differ from conventional solid media?
Semisolid media contains a 1.5% concentration of agar, which is used to grow and select isolated colonies. Semisolid media contains agar at a lower concentration (around 0.4%,) which is used for motility studies.
What type of semisolid medium is used to grow bacteria?
Agar is a semi solid medium used to grow bacteria.
What are the methods used for identifying motility?
There are two basic method to determine motility in a bacterial sample. These samples have similar biochemical identifiers. The first test is a simple drop test. The second method employs a motility medium
When testing microaerophils some microbiologists prefer to use a semisolid nitrate medium that contains a small amount of agar why is this done?
Microbiologists testing microaerophils prefer to use a semisolid nitrate medium that contains a small amount of agar to get more accurate results. This is also done to speed up the results.
Microbiology - what is SIM test?
Its a test where a semisolid agar called Sulfide-Indole-Motility medium (or SIM medium) is inoculated with a bacteria to test for hydrogen Sulfide, Indole, and Motility of the organism. The medium is inoculated by a swab and stab type method (rub some bacteria on the surface of the medium and stab a straight hole through the medium using a straight wire with the bacteria on it). Incubate the bacteria for about 24 hours and then begin testing.... If hydrogen sulfide is present, it will react with the sodium thiosulfate in the medium and the indicator, ferric ammonium citrate, to produce ferrous sulfide which falls out of solution as a blackish precipitate. The presence of hydrogen sulfide typically means that the bacteria produces the enzyme cysteine desulfanase which breaks up the cysteine in the medium into, among other components, hydrogen sulfide. The Indole portion of the test is performed by adding Kovac's reagent to the inoculated medium. The Kovac's reagent reacts with the indole(if indole is present) to produce a pinkish-red or redish-purple ring around the top of the test tube. If indole isn't present, there will be no color change. The presence of indole means that the bacteria produces tryptophanase, an enzyme which breaks down tryptophan into smaller components, one of which being indole. The Motility aspect of the test is done by checking the medium for turbidity, or "fuzziness". If the medium has become fairly turbid throughout the medium, then the bacteria is motile. If the medium is clear and the only turbid appearance is in the stab line, then the bacteria is non-motile. Unfortunately, the motility aspect of this test typically gives false negative results. Sometimes the temperature that the bacteria was incubated at wasn't optimum for the species, sometimes the bacteria only have weak motility, sometimes the bacteria's flagella can get damaged which would impair motility, etc... The point is, this test is good if you want to know whether or not the bacteria you're testing produces tryptophanase or cysteine desulfanase. The motility aspect of the test is suspect to question, at least if the test result was negative for motility(a large amount of turbidity in the medium is a definite sign of motility and is hard to refute though).
What factors dictate the choice of test in a combination medium?
Hydrogen Sulfide production, Motility, and Indole production.
When testing microaerophiles prefer to use a semisolid nitrate medium that contains small amount of agar Why?
microaerophiles grow below the medium surface of culture, in presence of oxygen required (equal or matched ) by them .
What factors dictate choice of tests included in a combination medium?
The hydrogen sulfide production, motility, and indole production.
What factors dictate the choice of tests included in a combination medium?
The hydrogen sulfide production, motility, and indole production.
If sim medium was used for motility determination for Proteus vulgaris what noticeable change to the medium will be observed?
It will turn black in the inoculation stab as well as throughout the medium because P. vulgaris is a flagellated and motile organism.
