What is the primary method for inserting engineered plasmids into bacterial cells?

The primary method for inserting engineered plasmids into bacterial cells is transformation. Transformation refers specifically to the process by which bacteria take up free, extracellular DNA from their environment. This can occur naturally in some bacteria, but in laboratory settings, it is often facilitated by techniques that make the bacterial cell membrane more permeable to DNA, such as heat shock or electroporation.

Transformation is widely used in genetic engineering to introduce plasmids, which are circular DNA molecules that can carry genes of interest into bacterial cells. Once inside, these plasmids can replicate independently of the bacterial chromosomal DNA, allowing for gene expression and the production of proteins encoded by the plasmid.

While transduction involves the transfer of DNA from one bacterium to another via a virus, and conjugation involves direct transfer of DNA through cell-to-cell contact, neither is the primary mechanism used to introduce engineered plasmids. Transfection, on the other hand, is a term more frequently used in the context of eukaryotic cells rather than bacteria. Therefore, transformation is the most accurate answer for the method of inserting engineered plasmids into bacterial cells.