Microbiology: Methyl Red Test — Transcript

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1. 0:00my name is Kevin toke off in this video
2. 0:01we're going to discuss the theory behind
3. 0:03the methyl red test ok so methyl red we
4. 0:07hopefully know by now we've seen it
5. 0:09enough it is a pH indicator that changes
6. 0:12colors when you fluctuate between
7. 0:14different PHS okay now in the methyl red
8. 0:19test what we're testing is the ability
9. 0:21of the bacteria to convert pyruvic acid
10. 0:24after glycolysis onto mixed organic
11. 0:27acids which we won't actually name those
12. 0:29but we're just testing its ability to
13. 0:31form mixed organic acids okay so I have
14. 0:34this little diagram here so we're gonna
15. 0:36start out with something that contains
16. 0:37glucose okay in fact we're gonna
17. 0:40actually start with glucose glucose will
18. 0:42go through glycolysis to form pyruvic
19. 0:45acid or pyruvate and then the pyruvic
20. 0:48acid could if the bacteria is able to do
21. 0:50this convert this to mixed organic acids
22. 0:53okay so as we start with glucose the
23. 0:57methyl red is actually going to be a
24. 0:59yellow color okay but as we go through
25. 1:03glycolysis to form pyruvic acid and then
26. 1:05further mixed organic acids the mixed
27. 1:08organic acids are actually going to
28. 1:10titrate the methyl red with the
29. 1:12decreasing pH to a red color okay so if
30. 1:16we're doing a methyl red test and we see
31. 1:18a red color develop that means that the
32. 1:22bacteria was actually able to convert
33. 1:25the pyruvic acid into mixed organic
34. 1:27acids after glycolysis okay one thing
35. 1:30you should note is that the results of
36. 1:33the methyl red test are very similar to
37. 1:35the results of what we're going to look
38. 1:37at in another video called the Voges
39. 1:38persk our tests they're very very
40. 1:40similar well let's actually take a look
41. 1:42at the specific results for the methyl
42. 1:44red test fairly straightforward if it's
43. 1:48yellow like this you can see here or up
44. 1:51here that is a negative methyl red test
45. 1:54that means that these bacteria do not
46. 1:56have the ability to convert pyruvate to
47. 1:59mixed organic acids over here we clearly
48. 2:03see this as red same thing over here
49. 2:06it's more diffuse here but the principle
50. 2:09is the same we have a red result for a
51. 2:11methyl red test that means that these
52. 2:13back to
53. 2:13do have the ability to convert pyruvate
54. 2:16into mixed organic acids okay
55. 2:20and like I mentioned when in the one of
56. 2:23the previous videos where we looked up
57. 2:24the in Dole test this is another test
58. 2:27that's used to differentiate
59. 2:28gram-negative bacillus bacteria okay
60. 2:32make sure to watch the demonstration on
61. 2:35this bit on this process the methyl red
62. 2:37test and then we're also in the next
63. 2:39video going to look at the Volks persk
64. 2:41our test thank you