Question

More than one answer may apply:

what would happen if a microbiology technician used an old bactertial culture (>24hr) to make the slide?

A) Nothing different would occur because the freshness of bacterial culture doesnt matter

B) Gram-positive organism can appear pink because old cultures tend to lose their ability to retain the crystal violet.

C) Gram-negstive organism can appear purple because old cultures tend to lose their ability to retain the crystal violet.

D) Gram-positive organism can appear colorless because old cultures tend to lose their ability to retain the crystal violet.

Answer 1

Choice B : Gram - positive organism can appear pink because old cultures tend to lose their ability to retain the crystal violet.

Choice D: Gram- positive organism can appear colorless because old cultures tend to lose their ability to retain the crystal violet.

Explanation: Gram (-) cells are always seen as gram (-) where gram (+) cells either can be seen as gram (-) or colorless due to the experiment error. Gram (+) suppose to be in  violet in color and gram (-) in pink color after the staining.

old culture (more than 24 hours) changes the cell wall of the bacteria due its aging results in ability to react with the gram stain. Other than this Older culture has high tendency to get contaminated so the results will not be accurate. The best culture incubation is 18-24 hours and also should avoid the use of culture older than 24 hours for a accurate result.

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