Final answer:
Transformation is the process in which bacteria take up plasmids from the surrounding environment, either from natural sources or introduced in a lab. The cell membranes are made permeable using techniques like heat shock or electroporation. Bacteria that successfully undergo transformation can be selected on antibiotic-containing media.
Step-by-step explanation:
The process where a bacterium takes up a plasmid from the surrounding solution is known as transformation. This biological technique allows bacteria to acquire new genetic material, notably plasmids, from their environment, which often comes from lysed cells or is introduced in a laboratory setting. During molecular cloning using transformation, plasmids are mixed with a culture of living bacteria. However, not all bacteria will incorporate these plasmids; some may take up nonrecombinant plasmids while only a few will integrate recombinant plasmids containing foreign DNA.
To facilitate transformation, bacteria are usually treated to become more permeable; for example, by exposure to CaCl2 and a subsequent rapid heat shock, which causes the bacterial cell membranes to form pores through which DNA can enter. An alternative method is electroporation, where electrical pulses create transient pores in the cell membrane. After transformation, bacteria are often cultured on a medium containing an antibiotic (often ampicillin) to select for the cells that have taken up plasmid DNA, as these will carry antibiotic resistance genes, allowing them to survive and form colonies while those without plasmids perish.