Lwoff , André Michael

(1902–1994) French biologist

Born at Ainy-le-Château in France, Lwoff graduated in natural sciences in 1921 and joined the Pasteur Institute in the same year. He went on to become head of the laboratory in 11929 and from 1938 was head of the microbiology department. Lwoff moved to the Sorbonne in 1958, where he served until 1968 as professor of microbiology.

During the 1920s he demonstrated that vitamins function as coenzymes and also found that certain characters of protozoans are controlled by genes outside the nucleus. His most notable work, however, was his explanation of the phenomenon of lysogeny in bacteria. Lysogenic bacteria contain the DNA of a virus in their own DNA, the virus duplicating along with the bacterial chromosome and being passed on to subsequent generations. The virus, however, is nonvirulent and rarely destroys its host. When Lwoff began his research the prevailing view of lysogeny was that the phage–host association rendered the bacteria resistant to later viral destruction and that this association was perpetuated by the added presence of exogenous bacteriophage on the surface of the host. Further, it was believed that the increase in phage numbers in a lysogenic bacterial culture was due to the presence of some susceptible bacteria. Lwoff showed firstly that exogenous phage were not necessary to the association, and secondly that the increase of phage numbers in cultures is due to a reversal of the phage state from nonvirulent to virulent, which leads to the multiplication of phage particles in the host and subsequent breakdown or lysis of the host with release of these particles. He named the noninfective structure in lysogenic bacteria the prophage, and showed that ultraviolet light is one agent that can induce the prophage to produce infective viral particles.

In recognition of this work, Lwoff received the 1965 Nobel Prize for physiology or medicine, along with François Jacob and Jacques Monod.