Question

what are the names of the two groups of bacteria resulting from the gram stain method?
a) gram - cocci and gram - rods
b) gram - variable and gram - constant
c) gram - visible and gram - invisible
d) gram - positive and gram - negative

Explanation:

The Gram - stain method is a common technique in microbiology. Bacteria are classified based on their cell - wall properties. Gram - positive bacteria retain the crystal violet stain (appear purple) because they have a thick peptidoglycan layer. Gram - negative bacteria lose the crystal violet stain during the decolorization step (after counter - staining with safranin, they appear pink) as they have a thin peptidoglycan layer and an outer membrane.

• Option a: Gram - cocci and Gram - rods refer to the shape (cocci - spherical, rods - rod - shaped) of bacteria, not the result of the Gram - stain.
• Option b: Gram - variable (bacteria that show inconsistent Gram - staining results) and Gram - constant (a non - standard term in this context) are not the main groups based on the Gram - stain principle.
• Option c: Gram - visible and Gram - invisible are not valid terms for classifying bacteria based on the Gram - stain.
• Option d: Gram - positive and Gram - negative are the two main groups resulting from the Gram - stain method.

Answer:

d) Gram - positive and Gram - negative