Biochemistry

Franz Lang uncovers the mystery of mitochondria

Franz Lang is best known as a key person who helped find the missing link between man and the bacterial world. The professor in the Department of Biochemistry finds ways to picture past evolutionary events by analyzing the DNA of immense datasets of existing organisms. He is an archaeologist, of sorts, but one who does not have the luxury of being able to brush off fossils.Lang does not mind missing out on that material evidence. “Those researchers studying the older fossils –say, about a million years old and not as old as what we’re looking at –could be seen at a disadvantage. They do not have ‘the luxury’ of analyzing DNA.”

Lang’s work concerns the mitochondrion, which has been called a power plant for eukaryotes, the organisms that allow animals and plants to grow. Mitochondria exist in eukaryotes but they’re not found in bacteria. Having or not having a mitochondrion has always been an important dividing line.Since one can’t just analyze human or animal cells to track our very early origins (We are much too evolved), Lang goes fishing for more primitive, less-evolved eukaryotic species. In the early ‘90s, his American collaborator Charley O’Kelly pointed him to an unnamed unicellular flagellate that O’Kelly had a hunch would become Lang’s time-traveling vessel. O’Kelly had named the tiny eukaryote Reclinomonas americana because of its reclining shape. But it would earn its fame more for the truly primitive genetic nature of its mitochondrial genome.

In 1997, Lang and his Université de Montréal colleagues Gertraud Burger and the late Robert Cedergren, along with several other team members culminated five years of work on the Reclinomonas mitochondrion. They sequenced and analyzed the DNA of the recliner and discovered it was the most primitive form of mitochondrial DNA known to date. Being much less evolved, it became easier to see its ancestry. To their amazement, they saw a number of typically bacterial genetic traits that are absent in human mitochondrial DNA. Their theories led to a clearer take on early evolution that had bacteria going into a type of witness protection program where its identity was completely changed to become a mitochondrion. The protected informant, seeking a safe haven, then completely lost its old network. It eventually evolved, according to Lang, into an absolute dependency of the bacterial partner on its eukaryotic host. So, in a more negative analogy, the eukaryotic cell had enslaved the bacterium, transferring its genes and functions to work for it.

That moment, when bacteria and mitochondrion began functioning symbiotically, set evolution in motion for the next billion or so years. It also makes Lang one of the most important people alive in this area, according to Indiana University’s Jeffrey D. Palmer. “His discovery in 1997, together with his major, long-term collaborators Gertraud Burger and Michael Gray, came as a great revelatory surprise, forming in many ways a vital missing link at the genomic level . ” Lang and Burger are members of a large collaboration involving researchers from six Canadian universities. The team of nine takes a unique look at the diversity of microbial eukaryotes, which are believed to carry more biochemical diversity than the whole kingdom of animals, plants and fungi combined.

It might be asking too much for him to achieve major breakthroughs like the one in 1997 on a regular basis but Lang is content to simply learn more about all the organisms he is analyzing. He continues to sequence their complete nuclear genomes that still lie as unexplored clues to our ancient past.