Transforming Factors

Transforming factors are substances isolated from pneumococci and some other bacteria that cause a permanent hereditary change in another strain of bacteria of the same type.

Transforming factors were first discovered in 1928 by Frederick Griffith during his experiments with pneumococci. Griffith showed that non-virulent strains of pneumococci can acquire virulent properties after incubation with killed virulent cells. He suggested that some substance secreted by virulent cells transforms non-virulent cells into virulent ones.

Later, in 1944, Oswald Avery, Colin McLeod and McLean McCarthy isolated DNA from virulent pneumococci and showed that it was the transforming factor. Their work proved that DNA carries genetic information.

In addition to pneumococci, transforming factors have also been found in other bacteria, including streptococci, staphylococci, and some Escherichia coli. These factors allow the transfer of genetic material between bacteria, which is important for the evolution and spread of traits such as antibiotic resistance.

Thus, the discovery of transforming factors was an important milestone in understanding the mechanisms of genetic transformation and the role of DNA as a carrier of hereditary information. Their study continues to this day, revealing new facets of the transfer of genetic material among bacteria.