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Ty Bookmarks People Tab Window Help x + K. Course Home 10 Multiple Choice Qu... One of the best col... QUESTION Zpes An unknown microorganism is contaminating your fish tank. You would like to quantify the amount of the unknown microbe in the water. You are currently taking microbiology and your professor allows you to use the resources in the laboratory. Describe how you would determine the concentration of microorganisms present in 1 ml of water from your fish tank. Also describe two tests you can perform on cultures isolated from your fish tank to start identifying the cause of contamination. These tests should focus on metabolic characteristics of the microbe, not structural characteristics (like shape and gram reaction). What will the tests you perform tell you about the contaminant? HTML Editore BIV AA- IEEIX X ! E DO ? Nv Debi @ TT 12pt - Paragraph - Ⓡ

Answer 1

ANSWER 1 :-

1. For determining the concentration of the unknown microbe, the water sample should first be taken. Lets consider the mentioned Volume of 1ml. This can then be plated on an agar plate having a specific media (if microbe is known) or a culture media which is non-specific (most microbes can grow).
2. The plate can then be used to measure the Colony Forming Units usually expressed in the form of CFU/ml.
3. This value indicates the concentration of the microbes in the specimen. Apart from this, OD measurement can also be taken at different time intervals to obtain the growth curve which can help to relate the Optical density with the concentration of the microbe in the water.

CFU/ml = Number of colonies seen / Dilution factor (10⁰ if not carried out) × Volume of sample added

ANSWER 2 :-

Test 1 :- Glucose fermentation test is the first test used to identify the microbes which are able to metabolize different substrates such as Glucose, lactose, maltose, etc which are carbon containing substrates. A researcher would be able to distinguish between certain strains of proteins depending upon their ability to metabolize the substrate maltose. This helps them to identify the strains specific to the substrate utilisation and provides a possible route to remove the unwanted alternative strains. Basically, after the process is complete, the media will contain acids and gases such as carbon dioxide which will lower the pH. This can be specified using a particular indicator dye and marks the presence of microbe.

Test 2 :- Citrate test is the second test which can be used to identify the microbes which are able to metabolize citrate as a potent carbon source. Microbes like Klebsiella sp. are able to metabolize the substrate and hence can be used to specify it from other microbial strains.

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