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tangare [24]
3 years ago
5

Biochemical and differential tests can be incorporated into growth media or performed on isolated colonies after they have been

cultured. Give three examples of a differential test that is incorporated into media and three examples that are applied after the colonies have been cultured.
Biology
1 answer:
Cloud [144]3 years ago
4 0
<h2>Differential test</h2>

Explanation:

A differential test helps to distinguish that which species lack or have the particular biochemical process,the three differential test media are:

1) Blood agar: Blood Agar is an enriched medium which is used to culture those bacteria or microbes that do not grow easily

  • It is also required to detect and differentiate haemolytic bacteria, especially Streptococcus species
  • It is also a differential media in allowing the detection of hemolysis (destroying the RBC) by cytolytic toxins secreted by some bacteria, such as certain strains of Bacillus, Streptococcus, Enterococcus and Staphylococcus

2) Eosin methylene blue agar (EMB): It is a selective and differential medium used to isolate fecal coliforms

  • Eosin methylene blue are pH indicator dyes which combine to form a dark purple precipitate at low pH; they also serve to inhibit the growth of most Gram positive organisms
  • Sucrose and lactose serve as fermentable carbohydrate sources which encourage the growth of fecal coliforms and provide a means of differentiating them

3) Mannitol Salt Agar (MSA): It is a selective and differential medium

  • The high concentration of salt (7.5%) selects for members of the genus Staphylococcus, since they can tolerate high saline levels
  • Organisms from other genera may grow, but they typically grow very weakly

Three examples of tests which are done on colonies are:

1) Catalase test: Catalase is an enzyme that breaks hydrogen peroxide (H2O2) into H2O and O2

  • Hydrogen  peroxide is often used as a topical disinfectant in wounds, and the bubbling that is seen is due to  the evolution of O2 gas
  • A small amount of growth from the culture is placed onto a clean microscope slide
  • Few drops of H2O2 onto the smear is added
  • A positive result is the rapid evolution of O2 as evidenced by bubbling
  • A negative result is no bubbles or only a few scattered bubbles

2) Indole test: The main requirement for a suitable indole test medium is that it contain

s a sufficient amount of tryptophan

  • Tryptone broth is commonly used
  • The tube of tryptone broth with a small amount of a pure  culture is inoculated
  • Incubation is done at 35°C (+/- 2°C) for 24 to 48 hours
  • To test for indole production, 5 drops of Kovács reagent is directly added to  the tube
  • A positive indole test is indicated by the formation of a pink to red color  in the reagent layer on top of the medium within  seconds of adding the reagent
  • If a culture is indole negative, the reagent layer will remain yellow or be  slightly cloudy

3) Urease test: Urease is a constitutively expressed enzyme that hydrolyzes urea to carbon dioxide and ammonia

  • The urease test identifies those organisms that are capable of hydrolyzing urea to produce ammonia and carbon dioxide
  • Urease test media contain 2% urea and phenol red as a pH indicator
  • An increase in pH due to the production of ammonia results in a color change from yellow (pH 6.8) to bright pink (pH 8.2)
  • Urea broth is a highly buffered medium requiring large quantities of ammonia to raise the pH above 8.0 resulting in a color change
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Zepler [3.9K]

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in the question number 7 the correct answer is true.  this is because the green plant is using energy from the such for the process of photosynthesis. photosynthesis is a process by which green plants make their own food using energy from the light. light energy is used to split the molecules of water to oxygen and hydrogen ions. oxygen is released into the atmosphere whereas hydrogen ions are used in the dark stage of photosynthesis a process referred to as carbon fixation. the end result of carbon fixation is production of organic compounds such as glucose, protein and lipids among others. these foods store energy in form of chemical energy. so arrow A represents transfer of solar energy to chemical energy


in the question number 8, the arrows that represent the release of carbon dioxide include arrow C and arrow F. in arrow C the process occurring is referred to as combustion and it occurs when hydrocarbon in fossil fuels reaction with oxygen in the presence of heat to produce carbon dioxide and water. the arrow F represents respiration, a process by which living cells manufacture energy in form of ATP from organic food such as glucose. respiration end products include water carbon dioxide and ATP. it is essentially the reverse of photosynthesis


in question number 9, arrow E represents cycling of carbon from living organisms to non-living organisms. this is because it is showing conversion of a carbon from the dead tree to fossil fuel. when plants and animals die and buried deep in the ground, they are slowly converted to fossil fuels which contain organic hydrocarbon compounds including petrol, kerosene and other compounds.


in question number 10, arrow B & C show the conservation of energy and mass. when living organisms die they are converted to fossil fuels which are used in industries to produce energy required for various activities. during this process carbon dioxide is released into the atmosphere and it is used by plants in the process of photosynthesis as shown by B. this is conservation of energy and mass the number of carbon in the fossils fuel initially came from living plants and when fossil fuel is combusted it produces carbon dioxide that will be used in the process of photosynthesis and cycle continues.      

4 0
3 years ago
A certain tree does not survive well with extreme temperature variations. Which of the following adaptations will most likely ai
Irina18 [472]

The answer is C. This is correct because if the tree is near the equator, it will constantly be hot nearly everyday, because the Sun points straight at the equator. Because there is only one temperature, the tree doesn’t have to worry about dealing with the cold, only the heat.

5 0
3 years ago
Help To Check This Also
FrozenT [24]
I think the first one is right !.... but the for the other one it's B .
4 0
2 years ago
In 2004, scientists announced the discovery of the fossil remains of some extremely short early humans on the Indonesian island
Alex

Answer: The most accepted guess is: By bamboo rafts.

Explanation:

There are two hypotheses.

The first is that they arrived on Flores as Homo erectus and then evolved to Homo floresiensis. The second is that they were already Homo floresiensis when they arrived. This second one is the more accepted hypothesis because it would take organization and language to accomplish this technological water transportation feat. Homo erectus is not known to have developed speech.

Now at the time this transport was estimated to have happened, 100000 years ago, the islands of Komodo and Flores were joined and visible from the mainland. Together they constituted a 19km wide straight visible that could be easily seen from the mainland. The Homo floresiensis tribes built bamboo rafts, or possibly some other floating apparatus made if wood, and sailed there. The islands then progressively drifted apart, isolating them.

PS: It is important to note that some things may have drove them there such as famine, violence, etc.

8 0
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Which structure is located between the trachea and a bronchiole?
VARVARA [1.3K]

Answer:

pharnyx

Explanation:

8 0
3 years ago
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