Metchnikoff, microbiologist extraordinaire

He was "a single-minded character absolutely and tenaciously devoted to a high purpose – the improvement of human life. [His biography] is a story of ‘struggles and adventures’, but they are wholly in the field of the investigation of Nature. We read here little or nothing of the quest for personal advancement, for fortune or official position. These things had no attraction for Metchnikoff.”

If I were able to go back in time and chat with any scientist, I would without a doubt pick the absolutely unstoppable Ukrainian scientist Elie Metchnikoff.

Hailed as the “Father of natural, cellular, and modern immunology”, this guy did it all. Elie Metchnikoff was born in 1845 as Ilya Ilyich Mechnikov (he later adopted a French styling of his name, and so I’ve written it in the manner in which he himself did at the end of his life) in Kharkiv, the second-biggest city in today’s Ukraine. In my world – the world of microbiology and immunology - Metchnikoff is especially famous for one particular experiment that is admirable for its simplicity. Indeed, as these writers put it, Metchnikoff often made use of simple experiments in combination with great, yet insightful, leaps of imagination throughout his career.

This famous experiment in question took place in Messina, a harbour city in Italy. There, he was focusing in one of his earlier fascinations: developmental biology, and in particular, the study of embryos. He wanted to understand the story of growing up from embryo to adult – in other words, how organisms developed from one single cell into complex structures. To do this research, Elie made use of animals like starfish. Metchnikoff noticed that the larvae of these marine animals included cells that could both move and, in and of themselves, digest things. In other words, these were cells that could move around and gobble up and digest things from their surroundings. This fascinated him, and he began to try to trace how the adult digestive system developed. He was sure that the “primitive” digestion of these larval cells were somehow involved in this history of the digestive system.

While playing around with his starfish larvae, Metchnikoff was, in his own words, “struck by a novel idea”. Could these cells, or cells similar to these mobile, digesting cells, be involved in “the defence of an organism against dangerous intruders”? According to Metchnikoff, he got so excited upon having this thought that before proceeding with any experiment, he had to take a walk on the beach to calm himself down. I can totally relate.

After his walk on the beach, Metchnikoff came up with a plan. If his hypothesis was correct, and these mobile, digesting cells were indeed involved in immune defense, then they should mob any incoming threat. How to test this? Well, Metchnikoff figured that if he stuck a thorn into a starfish larva, those cells should surround that thorn in an attempt to defend the larva against the intruding thorn.

And thus, he plucked some thorns from a rose bush in his garden, and stuck them in some starfish larvae. And then, he waited. Although not with great patience or peace of mind. Metchnikoff wrote in his memoir, My stay in Messina (Memories of the past):

“I was so excited I couldn't fall asleep all night in trepidation of the result of my experiment, and the next morning, at a very early hour, I observed with immense joy that the experiment was a perfect success! This experiment formed the basis for the theory of phagocytosis, to whose elaboration I devoted the next 25 years of my life.

Thus, it was in Messina that the turning point in my scientific life took place.”

Eventually, Metchnikoff would receive the 1908 Nobel Prize in medicine or physiology for his contributions to immunology, and for his discovery of the “phenomenon of phagocytosis with which his name will always be associated”. In its essence, “phagocytosis” describes how certain cells that travel around our bodies – and those of starfish – act as defenders against bacteria and other microbes by gobbling them up and digesting them, therefore destroying the harmful invaders. He was indeed correct, and this gobbling up of microbial invaders is a key stage in our body’s counterattack. If you want to know more about this, you can check out last week’s Microbial Mondays article.

To be fair, Metchnikoff was not the only, nor the first, person to observe phagocytosis, or even the first person to suggest that mobile, gobbling cells in “higher animals” – like us mammals, for example – might destroy those bacteria that they gobbled up. However, Metchnikoff was the first to prove this concept with his elegant starfish larvae experiment, and he also valiantly defended his theory throughout the rest of his career.

While reading about Metchnikoff’s life, as well as descriptions of his scientific work, I also came across many examples of his bravery, his dedication to his work, and his absolutely unstoppable approach to life. I would like to share a few of those stories with you.

As a boy, Elie Metchnikoff lived on his family estate in present-day Eastern Ukraine, where he was evidently awed by the beautiful natural world around him. By age six, he was using “his pocket-money to bribe anyone he could find to listen to his lectures on the local flora and fauna.” I can relate. I used to give (highly amateur) palaeontology lectures to my wonderful family members who kindly humoured me even in the absence of any monetary bribery.

I also had to giggle at how, while still studying at the lyceum at Kharkoff in his mid-teens, Metchnikoff wrote his first scientific paper, but then upon realizing that he’d made a mistake, suppressed it himself. Then, ever confident in his own abilities, “a year later he made himself thoroughly unpopular by publishing in the Journal de Moscou an adverse criticism of a geology book by a Kharkoff professor.”

One aspect for which I most respect Metchnikoff, is that this man did not tolerate breaches of integrity. After finishing his university course in only two years, he moved to Giessen, where he worked with a well-known taxonomist and parasitologist by the name of Leuckart. When Leuckart published work done by the young Metchnikoff without Metchnikoff’s consent or any acknowledgement of the young scientist, Metchnikoff’s response was to denounce Leuckart in a public letter.

This intolerance for any lack of integrity was a theme throughout Metchnikoff’s life. Later in his life, around the time of the assassination of Alexander II of Russia, Metchnikoff was teaching at Odessa University. When his liberal views came under suspicion in the politically fraught climate of the time, Metchnikoff chose to resign rather than compromise his own morals. He was terribly emotionally distraught by this, and as a result attempted suicide for the third time in a decade, by infecting himself with an infectious bacterium. Lucikly, he survived, and went on to eventually find a place where he was accepted, and celebrated, for who he was: the Pasteur Institute in Paris.

At the Pasteur Institute, Metchnikoff was known for never refusing “anyone who applied to work with him and thus had a constant and ever-increasing stream of students from all parts of Europe,” and for being “an ardent advocate of the policy of attracting people of unusual ability by paying them highly and of giving generous scholarships to young scientists starting out on a research career”. He was also a proponent of science communication, and wrote numerous articles and gave many public lectures and interviews to share his insights.

Metchnikoff wasn’t always right of course – although that is simply part of the human condition, I suppose. For example, in his later years he posited that the microbes that live in our intestines were basically rotting us from the inside – while we now know that they are necessary for our health. But, to give credit where credit is due, this idea led to him putting himself on “a 'hygienic diet' which consisted of avoiding all uncooked food, as well as alcohol and tobacco.” He was definitely on to something in terms of abstaining from those latter two substances in order to prolong his life. And, although his ideas about gut microbes weren’t exactly spot on, they did lead to later work which has led him to be hailed as not only the father of cellular immunity, but also as the father of probiotics.

Elie Metchnikoff remained fascinated by the gut until the end of his career. On his deathbed in 1916, some of his final words were, 'You will do my post-mortem? Look at the intestines carefully for I think there is something there now.'

And so, like many Ukrainians, Metchnikoff was an impressive human indeed. We can still be inspired of him: we can strive to never accept breaches of integrity.

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