What Makes A Bacterial Transformation?

Transformation is the process in which a bacterial cell takes up extracellular DNA. This can be especially useful for bacteria in order to acquire certain traits such as: antibiotic resistance, synthesis of catabolites, or any other trait that would help improve its survival. However, not all bacterial cells are naturally competent (able to naturally take up extracellular DNA). There are several techniques that can make cells artificially competent, some of which will be discussed later.

Bacterial transformation was discovered by Frederick Griffith, in his experiments with Streptococcus pneumoniae. Griffith's experiment involved the non-pathogenic rough strain (R strain) and the pathogenic smooth strain (S strain) of S. pneumoniae. The R strain was injected into live mice, and since it was the non-pathogenic strain, the mice continued to live. The S strain however, contains pathogenic properties and would kill the mice after injection. Griffith discovered that if he injected R strain cells into mice, then added heat killed S strain cells, the cells became
pneumoniae. Instead of using live mice, he designed an experiment to determine what molecule transformed the R strain to S strain cells. Avery set up a series of test tubes each containing R strain cells growing in culture along with the extract of heat killed S cells. Each tube was given a separate enzyme designed to target and degrade a certain class of biomolecule: proteases for proteins, RNases for RNA molecules, and DNases for DNA molecules. The cells were the plated on an agar to determine whether a transformation from R to S occurred. Cells from the protease and RNase tubes were smooth, indicating that transformation occurred. On the agar containing the cells from the DNase tube, however, the cells were still rough, indicating no transformation occurred. The substance responsible for transformation was