How does ONPG enter E coli?

ONPG (o-nitrophenyl-β-D-galactopyranoside) enters E. coli primarily through passive diffusion due to its small size and hydrophobic properties. Once inside the bacterial cell, it can be hydrolyzed by the enzyme β-galactosidase, producing o-nitrophenol, which can be detected colorimetrically. This process is often used in laboratory settings to study enzyme activity and bacterial metabolism.