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Why are some organisms positive in the ONPG Test but negative when tested for the ability to metabolize lactose?
Wiki User
∙ 15y ago
ONPG is for the detection of delayed lactose fermentation.
Wiki User
∙ 15y ago
In the ONPG test, organisms may be positive due to the presence of beta-galactosidase enzyme, which cleaves ONPG and produces a yellow color. However, in the lactose fermentation test, some organisms may lack other necessary enzymes or transport systems to fully metabolize lactose, resulting in a negative result despite having beta-galactosidase.
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