Give the various methods to make bacteria a competent host.

(N/A) $DNA$ is a hydrophilic molecule,so it cannot pass through cell membranes. To force bacteria to take up plasmids,the bacterial cells must be made competent. This is achieved through the following methods:
$1$. Chemical Treatment: Bacterial cells are treated with a specific concentration of a divalent cation,such as calcium. This increases the efficiency of $DNA$ entry through pores in the cell wall.
$2$. Heat Shock Method: $r-DNA$ is forced into these cells by incubating them with recombinant $DNA$ on ice,followed by a brief heat shock at $42^{\circ} C$,and then placing them back on ice. This enables the bacteria to take up the recombinant $DNA$.
$3$. Micro-injection: Recombinant $DNA$ is directly injected into the nucleus of an animal cell.
$4$. Biolistics (Gene Gun): Cells are bombarded with high-velocity micro-particles of gold or tungsten coated with $DNA$.
$5$. Disarmed Pathogen Vectors: These vectors are allowed to infect cells,thereby transferring the recombinant $DNA$ into the host.
$6$. Electroporation: Cells are subjected to high-voltage electric pulses to make the cell membrane permeable for $DNA$ entry.
$7$. Lipofection: Recombinant $DNA$ is encapsulated in a lipid layer,allowing it to pass through the cell membrane.