Counting these areas and multiplying by the dilution factor allowed him to calculate the number of viruses in the original suspension.

[5][6] Between 1918 and 1921 d'Herelle discovered different types of bacteriophages that could infect several other species of bacteria including Vibrio cholerae.

[5] Bacteriophages were heralded as a potential treatment for diseases such as typhoid and cholera, but their promise was forgotten with the development of penicillin.

Since the early 1970s, bacteria have continued to develop resistance to antibiotics such as penicillin, and this has led to a renewed interest in the use of bacteriophages to treat serious infections.

Through the influence of a friend of his late father, he earned a commission from the Canadian government to study the fermentation and distillation of maple syrup to schnapps.

[10][11] During this period, d'Herelle published his first scientific paper, "De la formation du carbone par les végétaux" in the May 1901 issue of Le Naturaliste Canadien.

He also studied a local fungal infection of coffee plants, and discovered that acidifying the soil could serve as an effective treatment.

This innovative approach to locust plagues anticipated modern biological pest control using Bacillus thuringiensis also known as Bt.

D'Hérelle and his family finally moved to Paris in early 1911, where he worked again as an unpaid assistant in a lab at the Pasteur Institute.

He got attention in the scientific community the same year, when the results of his successful attempt to counter the Mexican locust plague with Coccobacillus were published.

[3] At the end of the year, restless d'Hérelle was again on the road, this time in Argentina, where he was offered a chance to test these results on a much larger scale.

During World War I, d'Hérelle and assistants (his wife and daughters among them) produced over 12 million doses of medication for the allied military.

In 1915, British bacteriologist Frederick W. Twort discovered a small agent that infects and kills bacteria, but did not pursue the issue further.

In 1921, he managed to publish a monograph, The Bacteriophage: Its Role in Immunity about his works as an official Institute publication, by tricking Calmette.

During the following year, doctors and scientists across western Europe took a heightened interest in phage therapy, successfully testing it against a variety of diseases.

In 1924, 25 January, d'Hérelle received the honorary doctorate of the University of Leiden,[14] as well as the Leeuwenhoek medal, which is only awarded once every ten years.

The Conseil was put in place to prevent plague and cholera spreading to Europe, with special emphasis on the sanitary concerns about muslim pilgrim groups returning from Mecca and Medina.

D'Hérelle then used phages he collected from plague-infected rats during his 1920 visit to Indochina on human plague patients, with claimed success.

The Haffkine Institute had not used Martin's medium, which included macerated pig stomach and beef muscle that would offend Muslims and Hindus.

Morison wrote to the Government of India to invite d'Hérelle noting that he was "a consummate technician, and a "most inspiring worker."

[16] D'Hérelle refused a request the following year by the British government to work in India, as he had been offered a professorship at Yale University, which he accepted.

To counteract this trend, d'Herelle agreed to co-found a French phage-producing company, piping the money back into phage research.

He was welcomed to the Soviet Union as a hero, bringing knowledge of salvation from diseases ravaging the eastern states.

[19] Fortunes turned abruptly for d'Hérelle when Eliava fell in love with the same woman as Lavrenty Beria, head of the secret police.

Max Delbrück and the "phage group" used bacteriophages to make the discoveries that led to the origins of molecular biology.

Much of the initial work on the nature of genetic expression and its regulation was performed with bacteriophages by Francois Jacob, Andre Lwoff and Jacques Monod.

In fact, immediately before his studies of the structure of DNA, James Watson had earned his Ph.D. by working on a bacteriophage-related project in Salvador Luria's laboratory.

As one of the earliest applied microbiologists, d'Hérelle's microbe-centered worldview has been noted for its prescience, since microbes are playing increasingly important roles in bioremediation, microbial fuel cells, gene therapy, and other areas with relevance to human well-being.

The novel Arrowsmith written by Sinclair Lewis with scientific help from Paul de Kruif was based to a certain extent on the life of d'Hérelle.