The EMB (Eosin Methylene Blue) agar is a selective and differential agar medium. It contains sucrose and lactose as fermentable substrates together with Eosin Y and methylene blue dyes which in combination gives the agar its characteristic color when prepared and serves as a pH indicator as well as an inhibitor of growth of Gram-positive bacteria. Hence, it is primarily used to isolate Gram-negative fecal coliforms while some positive fecal coliforms such as Staphylococci are also able to grow.
These coliforms are of two types:
- Lactose or sucrose fermenting coliforms form metallic sheens on the agar as a result of acid production and the response of the indicator to the increased acidity.
- Non-lactose/sucrose fermenters are only able to produce acid by protein deamination. Hence they either form colorless or pinkish colonies on the agar
On the other hand, Mannitol salt agar is a selective and differential agar medium that is primarily used to isolate Staphylococcal bacteria. The presence of sodium chloride in the medium makes it a partial or complete inhibitor of other bacteria.
Hence, an unknown bacterium that forms colorless colonies on EMB will either be a non-lactose fermenting, Gram-negative coliform that will hardly grow on Mannitol salt agar, or a Gram-positive fecal Staphylococcus.
Staphylococci bacteria are of two types:
- Coagulase-positive will form yellow colonies on the Mannitol salt agar.
- Coagulase-negative will form red colonies on the Mannitol salt agar.
More about isolating media can be found here: https://brainly.in/question/7238948
The sulphur would lable the capsule and the phosphorous the nucleic acid.
<h3><u>Explanation</u>:</h3>
Hershey and Chase experiment included growing of the pages in two batches, one in presence of 35S and other in presence of 32P. They then infected bacterial cells with these phages, cleaned them and then centrifuge the cells to isolate the marked elements in bacterial cells.
This was done to isolate which part of the phage is actually infective. Sulphur being a part of the proteins will mark the capsule whereas DNA having the phosphate bridges will be marked by 32P.
Four daughter cells that are haploid
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Volcanic eruptions may occur in both locations, as the movement can cause the tectonic plates to allow magma through.
