In the Durham tube fermentation test each a. with beef extracts or peptone b. wi
ID: 86258 • Letter: I
Question
In the Durham tube fermentation test each a. with beef extracts or peptone b. with citrate as sole source of carbon c. a specified d. a and e The pH indicator phenol red a. green at acidic value b. red at acidic value c. yellow at acidic value d. black at acidic value If an organism ferment a sugar a. acid is usually produced b base is usually produced c. gas may also be end product d. a or a and e occur e. (b) and (c) occur E coli is a. a glucose fermenter b a gram negative bacterium c. a rod shaped bacterium d all of the above e. none of the above Methyl Red test is an important test in differentiating genera such as a. Escherichia, and Salmonella b. protease and Aeromonads c. mumps virus and prohormones d. a and b. e. a and c In the O/F glucose test, if an organism can metabolized glucose aerobically and anaerobically, this organism is said to be a. fermentative and oxidative in its metabolism b fermentative in its metabolism c, oxidative in its metabolism d none of the above Which of the following microorganisms will be positive for the citrate test? a. Enterobacter aero gents b. E call c. Pseudomonas aeruginosa d. none of the above Cytochrome oxidase occurs in a. bacteria that carry out fermentation b. bacteria that carry out oxidation c. Pseudomonas d. a and be. b and c Hydrogen peroxide is a highly reactive oxidizing agent that can damage essential molecules in the bacterial cell. To avoid this damage, aerobes produce the enzyme a. catalase b deaminase e. lipase d. caseins The enzyme nitrate reductase catalyzes a. the transfer of electron from cytochrome b to nitrate, reducing it to nitrite b. the transfer of electron from nitrate to cytochrome c the transfer of electron from cytochrome b to nitrite reducing it to nitrate d. none of the above transfersExplanation / Answer
22. Option –d
Reason:
Fermentation used to detect gas and acid production from carbohydrates, fermentation medium contains PEPTON ,an acid base indicator [PHENOL RED], an inverted tube [durham] to trap gas and 0.5-1.0% carbohydrates. Fermentation occurs with or without oxygen presence.
23. Option – c
Reason:
A solution of phenol red is used as a pH indicator, often in cell culture. Its color exhibits a gradual transition from yellow (max = 443 nm) to red (max = 570 nm) over the pH range 6.8 to 8.2. Above pH 8.2, phenol red turns a bright pink (fuchsia) color.
24. Option – d
Reason:
When the organism ferments carbohydrates, acidic organic by products (Lactic acid, formic acid or acetic acid) is accumulated which turns the medium into yellow color with reduction in the pH (acidic). The inverted Durham tubes will detect the presence of gas. The degradation of peptones in the broth may result in the production of alkaline end products, which will change the broth color to pink often at the top of the tube.
25. Option- d
Escherichia coli ( E. coli) is a gram-negative, facultatively anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms (endotherms). E. coli grows in a variety of defined laboratory media, such as lysogeny broth, or any medium that contains glucose, ammonium phosphate, monobasic, sodium chloride, magnesium sulfate, potassium phosphate, dibasic, and water.
26.Option- a
27. Option- b
28. Option- d
If the organism has the ability to use citrate, the medium changes its color from green to blue.Two bacteria (both Enterobacteriaceae) on citrate agar, shows a positive result are fratklesiella pneumonia and euria aurantia
29. Option- d
30. Option- a
31. Option- b