C. B. van Niel shows that photosynthetic bacteria use reduced compounds as electron donors without producing oxygen. Sulfur bacteria use H2S as a source of electrons for the fixation of carbon dioxide. He posits that plants use water as a source and release oxygen.

Gerhard J. Domagk uses a chemically synthesized anti-metabolite, Prontosil, to kill Streptococcus in mice. One of the first patients to be treated with Protonsil is Domagk’s daughter who has a streptococcal infection that is unresponsive to other treatments. Near death, she is injected with large quantities of Protonsil and makes a dramatic recovery. Domagk is awarded the Nobel Prize in Medicine or Physiology in 1939.

Wendell Stanley crystallizes tobacco mosaic virus and shows that it remains infectious. However, he does not recognize that the infectious material is nucleic acid and not protein. Together with Northrop and Sumner, Stanley is awarded the Nobel Prize in Chemistry in 1946.

George Beadle and Edward Tatum jointly publish a paper on their experiments using the fungus Neurospora crassa to establish that particular genes are expressed through the action of correspondingly specific enzymes. The first gene to be identified controlled the synthesis of an enzyme in a series that led to generation of niacin. This report is the genesis of the “one gene-one enzyme” concept. With Lederberg, Beadle and Tatum are awarded the Nobel Prize in Medicine or Physiology in 1958.

Salvador Luria and Max Delbruck provide a statistical demonstration that inheritance in bacteria follows Darwinian principles. Particular mutants, such as viral resistance, occur randomly in bacterial populations, even in the absence of the virus. More important, they occur in small numbers in some populations and in large numbers in other cultures. With Hershey, Delbruck and Luria are awarded the Nobel Prize in Medicine or Physiology in 1969.

Oswald Avery, Colin MacLeod, and Maclyn McCarty show that DNA is the transforming material in cells. They demonstrate that the transformation of Streptococcus pneumoniae from an avirulent type to a virulent type is the result of the transfer of DNA from dead smooth organisms to live rough ones. They also show that the transforming principle is destroyed by pancreatic deoxyribonuclease —an enzyme that hydrolyzes DNA —but is not affected by pancreatic ribonuclease or enzymes that destroy proteins.

Albert Schatz, E. Bugie and Selman Waksman discover streptomycin, soon to be used against tuberculosis. Streptomycin has the same specific antibiotic effect against gram-negative microorganisms as penicillin does on gram-positive ones. Waksman is awarded the Nobel Prize in Medicine or Physiology in 1952.

Joshua Lederberg and Edward L. Tatum publish the first paper on a type of bacterial mating called conjugation. The proof is based on the generation of daughter cells able to grow in media that cannot support growth of either of the parent cells. Their experiments showed that this type of gene exchange requires direct contact between bacteria. At the time Lederberg began studying with Tatum, scientists believed that bacteria reproduced asexually, but from the work of Beadle and Tatum, Lederberg knew that fungi reproduced sexually and he suspected that bacteria did as well.

Microbiologist John Franklin Enders, virologist Thomas H. Weller and physician Frederick Chapman Robbins together develop a technique to grow poliovirus in test tube cultures of human tissues. This approach gave virologists a practical tool for the isolation and study of viruses. Enders, Weller and Robbins were awarded the Nobel Prize in Medicine or Physiology in 1954.