Department of Cell and Molecular Biology

Popular Science Presentation

Look for pieces of Life’s puzzle

Puzzle cellIn addition to the visible life that surrounds us (humans, animals, plants, fungi, etc.), an invisible world exists that consists of microscopically small organisms, microbes. These microbes, also called prokaryotes, are relatively simple life forms, unlike the far more complex, eukaryotic cells that we humans are composed of. Ironically, or rather fascinating, the eukaryotic cells were once formed through a fusion of two kinds of microbial cells. The identity of the two fusion partners, as well as how the complexity of eukaryotic cells emerged, has long been a mystery. The aim of my research is to use novel, cutting-edge technology to identify the microbial ancestors of eukaryotic cells, and thus gain new insights into the emergence of complex life on Earth.

Ghost in our genes

How do we know that our ancestors can be traced to the simple microorganisms? The first clue comes from evolutionary studies of our genetic material with the same methods used in forensic investigations, in which DNA is collected from crime scene and compared with that of potential suspects. In evolutionary studies the "crime scene" is a complex organism and the potential suspects are microorganisms. By identifying microbial DNA sequences that match with DNA from complex organisms, we can identify microbes that played an important role in the formation of complex cells. Interestingly, evolutionary studies have identified two main groups from which complex cells emerged - a group of bacteria, known as the Alphaproteobacteria, and another group of microorganisms that was only recently discovered - the mysterious Archaea.

A happy microbial marriage

The evolutionary signals that scientists discovered in our DNA suggests that both bacteria and archaea played a role in the emergence of complex life - but how? In recent decades, scientists have tried to formulate evolutionary hypotheses that can explain these observations. Currently, the most plausible scenario is an intricate cellular cooperation - a "marriage between microorganisms" - between archaea and bacteria, in which an alphaproteobacterium is eventually taken up by an archaeal host cell. Beyond that, however, everything shrouded in mystery, we can only guess at the answers to these questions: Why and how did the bacterium and the archaeon end up in this "microbial marriage"? What caused the emergence of eukaryotic complexity, such as the cell nucleus? Why has complex life seemingly only evolved once during the evolution of life on Earth? To find answers to the questions we need to know more about the microbial bride and groom of this remarkably happy cellular marriage.

A powerful new tool to track our microbial ancestors

​In my research group we are looking into how complex life might have arisen on Earth. Powerful new methods will be developed and utilized to explore the enormous, uncharted, microbial diversity that exists in nature. We will look, for example, for archaea that possibly represent an intermediate stage in the transition from organisms that have simple cell types (prokaryotes) to those who have complex cells that we humans (eukaryotes). This will lead to unique opportunities to obtain more pieces of the puzzle that is our ancient evolutionary history.