An Accidental Breakthrough: Bacteriophage Discovery

Based largely on The Forgotten Cure (2012) by Anna Kuchment .

Bacteriophages are incredibly tiny bacteria-killing viruses that most people don’t even know about, let alone think about often. You may however have noticed a bit of a theme in the many blog posts here, we sure do love to talk about these invisible assassins! The way we get so excited about these viruses must make them seem like a revolutionary new discovery in microbiology. While it is true that great progress is being made when it comes to learning more about phages, and they seem to hold great promise to solve many issues we face today (see my previous post, or some of the other posts by my fellow phage hunters), the discovery of bacteriophages actually occurred almost exactly 100 years ago.

The discovery, though very exciting at the time came to be overshadowed by the rise of antibiotics, and it is only recently that the western world has begun to pay attention to bacteriophages once more. Therefore I thought it might be interesting to take a look at just how bacteriophages came to be known to science in order to see just how far things have changed.


So before I start let me set the scene. It’s the late 1880s and a young gentleman by the name of Felix D’Herelle has just graduated from high-school. Idealistic, self-confident and somewhat cocky, the young man is on a boat returning from Rio de Janeiro to his home city of Paris. As a graduation gift from his mother, D’Herelle had just finished an exciting 3 month trip around South America when yellow fever, a deadly mosquito-borne disease broke out among the ship’s occupants. Passengers and crew alike perished from the disease, and despite the horrors D’Herelle witnessed it was here that it became clear to our intrepid young adventurer that his life calling was study infectious diseases such as yellow fever.


He wrote in his memoirs;

“It is probable that I have, by birth, the first required quality needed to make a good microbe hunter. Most of the passengers were in anguish: I was perfectly calm, I thought I was invincible.”


Felix D'Herelle

Figure 1: Felix D’Herelle. Look at this twirly mustachioed rascal. Of course he’d end up in a life or death situation and immediately think about career prospects.

In 1894 D’Herelle moved back to his city of birth, Montreal, and set up his own home laboratory. Despite no formal scientific training, through family connections D’Herelle landed a government position studying fermentation. His lack of formal qualifications didn’t stop D’Herelle from accepting position after position studying fermentation and pest control – including becoming involved in innovative research in locust control using bacteria.

A few years later in 1911 D’Herelle moved back to Paris for an unpaid assistant position at the newly formed Pasteur Institute. With a wealth of knowledge and experts in the quickly blossoming field of microbiology at his disposal, D’Herelle was quickly at work pursuing his own research.


Now, before I go on to describe the actual discovery of bacteriophages is important to mention that our intrepid protagonist was not actually the first scientist to publish an academic work describing the phenomenon of bacteriophages.Two years prior to D’Herelle’s discovery a British scientist Fredrick William Twort who described small clearings in his bacterial colonies that we would describe as plaques (See Fig. 2 for an example), indicating the presence of phage. Twort however, attributed these to be a transparent product of the bacteria and thus since D’Herelle was the first to propose that the phenomena was caused by a different organism entirely, the credit for the discovery is shared between the two scientists.



Figure 2: An agar plate containing a lawn of Mycobacterium smegmatis (the white, more opaque part), and showing characteristic plaques (the more transparent circular clearances) which are formed by phage infecting and killing bacterial cells in those areas.

As for D’Herelle’s discovery of bacteriophages, like Twort his attention was brought to phages because of their infection of bacterial cultures he was cultivating as part of another project in which he was studying locust control. When small, transparent clearances appeared on his bacterial lawn D’Herelle was puzzled. Unable to replicate the results of these infected cultures and unable to observe the phages under the light microscopes that were available at the time, D’Herelle assumed that the plaques must have been somehow related to the disease of the locusts.

It was only years later in 1916, during World War I when D’Herelle was studying stool samples from soldiers infected with dysentery on the battlefront that he noticed the plaque phenomenon once more. This was a game-changer as it demonstrated to D’Herelle that this was not an event exclusive to the coccobacilli bacteria he studied in the locusts, but could occur in multiple kinds of bacteria from multiple hosts.


Figure 3: Photo showing German soldiers in a stormed french trench position on the Western Front during World War I. In the abysmal conditions of the trenches, it’s easy to see why disease killed so many soldiers during WWI. Virulent bacteria and by extension their bacteriophage adversaries would thrive in these close quarters.

Perhaps the most important aspect of the discovery was that D’Herelle noticed that plaques only seemed to appear in the bacterial samples from patients that seemed to be recovering from dysentery. The idea that whatever was causing the plaques could help fight disease was something that D’Herrelle immediately ran with.


D’Herrelle dived headfirst into his new discovery, conducting a test where he created a bacterial culture from a dysentery sufferers’ stool and filtered the bacterial culture along with an early form of the phage broth we used in the lab through a ceramic filter. He then added this filtrate to a liquid sample of the patient’s dysentery-causing bacteria and compared it to a control tube containing only bacterial sample and his early phage broth. For a few days the affected patient showed no sign of recovery and both test tubes were cloudy from bacterial growth. The next morning the tube with the filtrate was completely clear while the control tube was still cloudy from bacteria. Even more remarkably the patient was quite miraculously feeling a lot better.

D’Herelle was now certain that whatever was in the filtrate had the ability to kill the disease-causing bacteria, and thus he gave bacteriophages their name which means “bacteria eater.”


The method D’Herelle used was in principle the same method we used in our phage identification, but instead of using liquid cultures and judging phage presence based on the amount of bacteria present, we poured our filtrate onto a lawn bacteria and used plagues as indication of phage.


What followed was a paper published by D’Herelle in 1917 outlining his new discovery, and multiple trials by him and other researchers using isolated phage to treat illness. Some of these medical trials showed extremely promising results, with one study by physicians at the Baylor University College of Medicine in Dallas reporting 90% survival rate in a group of children suffering from dysentery that were treated with phage, as opposed to a 60% survival rate in the untreated control group. [1] Numerous reports of great success meant that phage therapy only became more and more popular as time went on, before the discovery of antibiotics of course.


D’Herelle’s discovery did not go unchallenged however. In his first 1917 report the scientist made some very bold guesses as to the nature of bacteriophages, some of which were flat out wrong and contradicted much of the emerging discoveries of the time.

By conducting tests that showed that a small dose of bacteriophage was just as effective as a large dose, D’Herelle correctly asserted that bacteriophages were living organisms as they must be capable of reproduction.

One of his more dubious suggestions was that bacteriophages were actually the “true microbe of immunity” which helped fight off disease in humans.This was in direct opposition to the work of Jules Bordet, his colleague at the Pasteur Institute who won a Nobel Prize for his work with antibodies in the blood and their involvement in the human immune system.

Furthermore while D’Herelle noticed that bacteriophage were specific to certain strains of bacteria, he suggested that phages could adapt to new strains by a process of acclimatization (exposure to other bacteria). We know now that phage can only adapt to infect new bacterial hosts due to mutations, but often at the cost of their ability to infect their previous host as bacteria posses quite specific and complex defense mechanisms against bacteriophages.


All and all despite D’Herelle’s lack of formal training and some dubious hypothesis along the way, his determination and ingenuity led to a discovery that would be built upon by countless scientists to come and be used for a variety of tasks. From phage therapy treating bacterial infections to transgenic organisms made using bacteriophage vectors, we owe a lot of what we know and can do today at least in part to Felix D’Herelle. What must have seemed like an annoying blight on his bacterial cultures turned out to be such a massive stroke of luck!


If you enjoyed this story you might enjoy The Forgotten Cure (2012) by Anna Kuchment [2], upon which I based a lot of this blog on. It’s a fairly light and compact recounting of the history of bacteriophage and goes into more detail about the rise and decline of phage therapy and what occured after D’Herelle’s disovery.



Figure 1: Ryzhikov, B.A., N. Devdariani, & Various at Pasteur Museum. (14 Mar 2017). Under the Sign of Bacteriophage. Science First Hand, 46.

Figure 2: Photograph taken by Leani Oosthuizen

Figure 3: INTERFOTO / Alamy Stock Photo.


  1.  MacNeal, W. J. and Frisbee, Frances C.: Bacteriophage as a Therapeutic Agent in Staphylococcus Bacteremia, Journal of the American Medical Association 99: 1150–1155 (Oct. 1) 1932.

2. Kuchment, A. (2012). The Forgotten Cure: The Past and Future of Phage Therapy. New York, NY, USA: Copernicus Books.

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One Response to An Accidental Breakthrough: Bacteriophage Discovery

  1. jcturnbullnz says:

    Hi Leani! I enjoyed reading your blog, learning a bit more about this history and the humour you used in the post. It must have been so challenging for scientists back then to identify new organisms and characterise them, which I find really interesting

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