Because of a snowstorm, your regular laboratory session was cancelled and the gram staining procedure performed on cultures incubated for a longer period of time. Examination of the stained B. cereus slides revealed a great deal of color variability, ranging from an intense blue to shades of pink. Account for this result.

Bacillus cereus are Gram-positive, rod-shaped bacteria that form orange-pink colonies in agar media (e.g., BACARA medium, which is used for detection and enumeration of B. cereus). In this case, it is expected that after a long time without taking care of the culture, the bacteria started to die. Subsequently, lysed bacterial cells lost their dye which accumulated in some areas of the medium, thereby showing different colors ranging from an intense blue (areas with dead bacteria) to shades of pink (areas with bacteria still alive and viable).

priyankatutor priyankatutor · Answer 2 · 2021-12-23T11:12:46+01:00

The color of some colonies are changing bacause of long incubation due to death of bacteria.

Bacara agar medium:

It is used for detection and enumeration of B. cereus. Bacteria gives orange-pink colonies in the media.

This detection method only detects the live bacteria, but here bacteria are dieing because of lake of food in media.

Therefore, the color of some colonies are changing bacause of long incubation due to death of bacteria.

To know more about Bacara agar medium:

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