In search of the microbial origin of life
In biology, there are three known domains of cell-based life: eukaryotes – which include humans – bacteria and archaea. A research team from the Cluster of Excellence "Balance of the Microverse" at the University of Jena is now searching for a possible transitional form between eukaryotes and prokaryotes, which could potentially form a fourth domain of life. The Volkswagen Foundation is supporting this pioneering project, which could bring about a scientific paradigm shift if successful, with around 1.4 million euros over the next five years, starting today, 1 August 2025.
The unknown unknown
‘Research is, of course, always a search for the unknown, but there are different types of unknown,’ explains Christian Jogler, Professor of Microbial Interactions at the University of Jena, adding: "On the one hand, there is the known unknown, which we know exists but do not yet understand – such as dark matter in astrophysics. Even more difficult to grasp, however, is the unknown unknown, which we do not even know exists. Discovering such an unknown unknown leads to truly significant paradigm shifts in science, such as the discovery that it is not the Earth but the Sun that is at the centre of our planetary system."
As a microbiological example, Jogler cites predatory prokaryotes, i.e. microbes without a cell nucleus that hunt other bacteria for food. According to the previous state of scientific knowledge, this hunting behaviour was supposed to be reserved for eukaryotes, i.e. cells with a cell nucleus. Since this was considered a fact, no one looked for predatory prokaryotes. Nevertheless, in 2024, Prof. Jogler's team succeeded in finding, isolating and describing such a bacterium off the coast of Helgoland.
A microbial Archaeopteryx?
But how do you search for something you know nothing about? ‘Thought experiments help here: we suspect that there must have been a transitional form between prokaryotes and the more complex eukaryotes, a kind of microbial Archaeopteryx,’ explains the microbiologist. Similar to how Archaeopteryx exhibited characteristics of both dinosaurs and modern birds, the suspected microbes should exhibit characteristics of both prokaryotes and eukaryotes. ‘However, the comparison with Archaeopteryx also highlights the risk involved in this search,’ adds Jogler. ‘After all, it is extinct. So it may be that we find nothing in our search because this species no longer exists – or because it never existed in the first place.’ It is precisely this uncertainty, combined with the possibility of significant discoveries, that is a decisive criterion for the five-year funding in the Pioneer Projects – Explorations of the Unknown programme by the Volkswagen Foundation.
In addition to searching for the link between prokaryotes and eukaryotes, the project team also wants to get as close as possible to the origin of cellular life itself. To this end, the researchers have postulated the existence of a fourth domain of life, which they call ‘Planctomycia’, based on the 4D hypothesis.
New technologies for microbiology
To achieve these ambitious goals, Christian Jogler's research group is developing a completely new technique called ‘microscale microbiology’. ‘With this method, we can directly observe, manipulate and genetically characterise individual bacterial cells without having to rely on lengthy cultivation processes,’ explains Jogler. The technology could also be used in medical diagnostics in the future, for example to quickly determine the optimal antibiotic therapy for infectious diseases.