Tests for bacterial motility: Difference between revisions
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* Used to detect bacteria that are motile |
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There are a variety of ways to determine motility of a bacteriumβbiochemical tests as well as microscopic analysis. If fresh culture of bacteria is available, microscopy is the most accurate way to determine bacterial motility and '''βHanging drop methodβ''' is a commonly used microscopic technique. |
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* Tube motility |
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** Stab an inoculum down into a tube with semisolid agar |
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** Check at intervals for diffuse, fuzzy growth that appears outside of the stab line |
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* Wet prep |
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** Put a drop of inoculum in distilled water and check under a microscope |
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** Can compare to a drop of peptone water to identify [[Vibrio]] (motile in peptone water, not distilled) |
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[[Category:Diagnostics]] |
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Motile bacteria move about with structures called '''flagella''' (a few exceptional bacteria move with the help of axial filaments, which cannot be seen in the microscope). In semi-solid agar media, motile bacteria βswarmβ and give a diffuse spreading growth that is easily recognized by the naked eye. |
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= Procedure = |
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# Prepare a semisolid agar medium in a test tube. |
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# Inoculate with a straight wire, making a single stab down the center of the tube to about half the depth of the medium. |
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# Incubate under the conditions favoring motility. |
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# Incubate at 37Β°C |
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# Examine at intervals, e.g. after 6 h, and 1 and 2 days ''(depends on generation time of bacteria). Freshly prepared medium containing 1% glucose can be used for motility tests on anaerobes.'' |
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= Results = |
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Hold the tube up to the light and look at the stab line to determine motility. |
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# Non-motile bacteria generally give growths that are confined to the stab-line, have sharply defined margins and leave the surrounding medium clearly transparent. |
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# Motile Bacteria: typically give diffuse, hazy growths that spread throughout the medium rendering it slightly opaque. |
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[https://i0.wp.com/microbeonline.com/wp-content/uploads/2015/10/Test-for-Bacterial-Motility.png [[File:https://i2.wp.com/microbeonline.com/wp-content/uploads/2015/10/Test-for-Bacterial-Motility-300x210.png?resize=300%2C210|Test for Bacterial Motility: Center (Non-motile); Corners (Motile)]]] |
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Test for Bacterial Motility: Center (Non-motile); Corners (Motile) |
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= Laboratory Use = |
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In laboratory Motility testing using semi-solid medium is commonly used for the identification of gram negative bacteria of '''Enterobacteriaceae family.''' Motility testing is done in conjunction with other biochemical testing using special bio-chemical media. |
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# Sulfide Indole Motility '''(SIM)''' Medium: It is a semisolid agar used to determine hydrogen sulfide (H2S) production, '''indole formation,''' and '''motility.''' |
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# Motility Indole urease '''(MIU)''' test: It is used to determine Motility, indole formation and '''Urease Test.''' |
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Motility test is also used for the species differentiation of gram positive cocci, Enterococci. ''Enterococcus faecium'' and ''E. faecalis'' are non-motile, whereas ''E. gallinarum and E. casseliflavus/E. flavescens'' generally are motile. |
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'''Note:''' Incorporation of tetrazolium chloride at a final concentration of 0.005% in the medium is helpful. The tetrazolium makes the motility agar much '''easier to read''' for motility. Tetrazolium is colourless in oxidized form, but the '''reduced salt is red''' (occurring as a result of bacterial metabolism) and indicates where bacterial growth has occurred. |
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= Specific tests for bacterial motility determination = |
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== Distilled water motility test == |
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It is a simple and very useful test to differentiate ''Vibrio species'' (gram negative motile curve rod) and ''Aeromonas species'' (gram negative motile rod). Aeromonas species will grow on [https://microbeonline.com/macconkey-agar-mac-composition-preparation-uses-and-colony-characteristics/ '''MacConkey agar'''] and sometimes on [https://microbeonline.com/thiosulfate-citrate-bile-salts-sucrose-tcbs-agarcomposition-uses-colony-characteristics/ '''TCBS'''], producing yellow colonies. Both of them are [https://microbeonline.com/oxidase-test-principle-procedure-and-oxidase-positive-organisms/ '''oxidase''' ]positive. |
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'''Procedure:''' |
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# Mix a loopful of growth from a nutrient agar subculture in a drop of sterile distilled water on one end of a slide. On the other end of the slide, mix another loopful of growth in a drop of peptone water. |
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# Cover each preparation with a cover glass. |
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# Examine microscopically using the 40 objective. |
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'''Results:''' '''All Vibrio species are immobilized in distilled water but remain motile in peptone water'''. ''Aeromonas'' species remain motile in distilled water and peptone water. |
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[[Category:Methods in microbiology]] |
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Latest revision as of 21:13, 28 January 2022
- Used to detect bacteria that are motile
- Tube motility
- Stab an inoculum down into a tube with semisolid agar
- Check at intervals for diffuse, fuzzy growth that appears outside of the stab line
- Wet prep
- Put a drop of inoculum in distilled water and check under a microscope
- Can compare to a drop of peptone water to identify Vibrio (motile in peptone water, not distilled)
