Final answer:
The Gram stain is a differential staining technique used in microbiology to detect differences between bacteria with different cell walls. Gram-positive bacteria retain the stain and appear purple, while gram-negative bacteria do not retain the stain and appear pink.
Step-by-step explanation:
The Gram stain is a type of differential staining technique used in microbiology to detect differences between microbes or parts of the same microbes.
It was developed by Da nish microbiologist Hans Christian Gram in 1884. The Gram stain allows microbiologists to distinguish between bacteria with different types of cell walls, specifically gram-positive and gram-negative bacteria.
Gram-positive bacteria retain the violet primary stain and appear purple-blue under the microscope, while gram-negative bacteria do not retain the primary stain and appear pink-red after taking up the counterstain.
The differences in staining are due to the differences in the cell wall composition of the bacteria.
Gram-positive bacteria have a thicker peptidoglycan layer, which retains the violet stain, while gram-negative bacteria have a thinner peptidoglycan layer covered by an outer membrane that does not retain the stain.