Tore Midtvedt died on 2 December 2025 at the age of 91. It is hard to grasp that the grand old man of gut microbiota research, whose work spanned three generations, is now gone.
Tore studied medicine in Oslo and Bergen, specialising in medical microbiology. He obtained his doctorate from the Karolinska Institutet in 1968 and subsequently held a number of positions at Rikshospitalet and the University of Oslo before being appointed Professor of Medical Microbial Ecology at the Karolinska Institutet in 1983. He became professor emeritus in 1999 and continued his research work up until his death.
Tore's list of achievements and honours is impressive: it includes the supervision of more than 50 doctoral candidates, the evaluation of doctoral theses and professorial appointments in at least six countries, as well as countless articles and lectures. For many years, Tore served as Editor-in-Chief of Microbial Ecology in Health and Disease. He was awarded an honorary doctorate by the Faculty of Veterinary Medicine at the Norwegian University of Life Sciences in 2010 and was appointed Knight First Class of the Order of St Olav in 2018. Tore was a member of the Agder Academy of Sciences and Letters and was affiliated with the Old Herborn University Foundation. Tore Midtvedt leaves a profound and lasting legacy, extending far beyond the traditional field of microbiology and well beyond Norway's borders.
Tore was a distinctive and charismatic scientist who dared to challenge established paradigms. He recognised early on that the gut microbiota performs a wide range of essential functions beyond simply affecting stool characteristics. By comparing test animals with and without bacteria, he established methods for assessing the functional roles of the gut microbiota. In a seminal study published in Science in 1996, Tore and his colleagues demonstrated how the gut bacterium Bacteroides thetaiotaomicron communicates with its host. He played a pivotal role in the development and testing of microbiome-based therapies and was involved in The Microbiota Vault, a global initiative established to safeguard microbial diversity, similar to the Svalbard Global Seed Vault. Tore had a rare ability to view medicine – and the world in general – from the perspective of microbes. He embraced diversity, relished speed and excitement, and possessed a finely tuned, warm sense of humour.
What if the gut microbiota plays a key role in the path to eternal life? In the novel After Many a Summer (1939), Aldous Huxley (1894–1963) writes about the Fifth Earl of Gonister, who lives for more than 200 years by consuming the gut flora of carp, only to transform into a grotesque, animalistic creature. Tore, of course, understood the deeper meaning: everything has its proper time under heaven.
We are grateful for all that we experienced with and learned from Tore, and we extend our warmest thoughts to his wife Kari, his sons, Karsten, Per and Øyvind, and to his extended family.