Melissa is studying a gram-stained slide of curd bacteria. she sees many rod-shaped, violet-colored bacteria.

what type of bacteria are they?

They are gram positive bacteria

Explanation:

To find out if the bacteria is gram negative or gram positive, the Gram Test is done. This test allows bacteria to be viewed under the light microscope, since without staining it is impossible to observe or identify their structure. The Gram Test involves 3 main steps:

• Crystal violet staining (a water soluble dye, purple);

• Discoloration (using ethanol / acetone);

• Counterstaining (using Safranina dye, red).

After the test, bacteria that are violet-colored in the dye (such as the bacteria Melissa is observing) are called Gram positive. Gram-positive bacteria retain the violet crystal due to the presence of a thick layer of peptidoglycan (a polymer made up of sugars and amino acids that originates from a mesh outside the cell membrane of the bacteria) in their cell walls, showing the color Violet.  Gram-negative bacteria, on the other hand, have a thinner peptidoglycan wall that does not retain the violet crystal during the discoloration process and are red in the final staining process.

b

explanation:

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