The lactose present in the growth medium of bacteria is transported to the cell by the action of

The correct option is Permease.

To understand how lactose is transported into bacterial cells, we can look at the structure and function of the *lac* operon in bacteria such as Escherichia coli. The *lac* operon is a cluster of genes required for the transport and metabolism of lactose. It consists of three structural genes:

1. *lacY* Gene: This gene encodes the enzyme permease (specifically, lactose permease). Permease is a membrane-bound transport protein that increases the permeability of the cell membrane to beta-galactosides, allowing lactose present in the external growth medium to be actively transported into the bacterial cell.
2. *lacZ* Gene: This gene encodes beta-galactosidase, which hydrolyzes lactose inside the cell into its constituent monosaccharides, glucose and galactose, so they can be used as carbon and energy sources.
3. *lacA* Gene: This gene encodes thiogalactoside transacetylase (acetylase), which transfers an acetyl group from acetyl-CoA to beta-galactosides, though its precise physiological role in lactose metabolism is less critical than the other two.

Other options such as polymerase refer to enzymes responsible for synthesizing nucleic acids (DNA or RNA) and are not involved in sugar transport.

Thus, the transport of lactose from the growth medium into the bacterial cell is facilitated specifically by the action of permease.