The geneticist Esther Lederberg is best remembered for discovering the lambda phage, a virus that infects and can kill the bacterium Escherichia coli. Her discovery had a considerable influence in virology and molecular genetics.

It led to crucial research that demonstrated how phages can transfer genes between bacteria and advanced our knowledge about, among other things, how genes are regulated and how pieces of DNA break apart and recombine to make new genes.

Phages (short for bacteriophage) are a virus that reside in a bacterial cell. They were discovered in 1917 by the French-Canadian microbiologist Félix d’Hérelle who called them “invisible, antagonistic microbes”. They were tried out as anti-bacterial agents but proved to be less practical than antibiotics when these were developed later.

The lambda phage is a specific type of virus called temperate, meaning that it lives for some time inside a cell rather than reproducing itself and then killing the cell immediately. It can live in its host’s DNA for as long as the cell is alive. The phage replicates and kills the bacteria only when the cell is starved of nutrients, or otherwise stressed. Many animal viruses have similar life cycles to lambda phage, including tumour and herpes viruses.

Esther Miriam Zimmer Lederberg was born in 1922 in New York. She graduated from Hunter College, New York, in 1942 and took her master’s degree in genetics at Stanford University, California, in 1946. She was then awarded a US Public Health Service Fellowship for research and went to the University of Wisconsin where she received her PhD in 1950.

In 1959 Lederberg returned to the School of Medicine at Stanford and became a professor in the Department of Microbiology and Immunology. She retired in 1985 and was appointed Professor Emeritus of microbiology and immunology.

She discovered the lambda phage in 1950, more or less by accident. She was growing

E. coli bacteria in Petri dishes when she noticed that some of the colonies looked odd, as if something was eating them. She retrieved some material from the gaps in the colonies and discovered that it could do the same thing in other bacteria. The material was the lambda phage.

Although Lederberg made pioneering discoveries in microbiological genetics, her work was overshadowed by the discoveries of her first husband, Joshua Lederberg, who was awarded the Nobel Prize for Physiology or Medicine in 1958 for his discoveries in how bacteria replicate.

Working with her husband, Esther Lederberg developed, among other things, replica plating, a technique for rapidly screening bacteria for desired mutations.

The research of several Nobel prizewinners depended to a significant extent on her contributions. She was an excellent experimental scientist, and a meticulous researcher with a photographic memory. Many researchers around the world have greatly benefited from her methodical records.

She combined her passion for science with a devotion to Medieval, Renaissance and Baroque music, and she was an enthusiastic recorder player.

She was a pioneer of women’s rights — when she became a professor, women were rare in university science faculties. Her colleagues remember her for her great charm and excellent sense of humour.

She was married twice. She was divorced from her first husband in 1966. Her second husband, whom she married in 1993, survives her.

Professor Esther Lederberg, geneticist, was born on December 18, 1922. She died on November 11, 2006, aged 83