A Microbe’s Gift of Life

                              

Breaking down the microbiology world one bite at a time


A Microbe’s Gift of Life

‘Twas the night after Christmas, three billion years ago… The first organisms are still digesting their holiday dinner. In the leftovers of some tasty primordial soup, the first organisms are playing with enzymes – discovering what it means to be alive. It’s a mayhem of molecules, and nobody knows what organism is doing what exactly. The organisms themselves might not even have a clue.

Primordial soup is served! (Source: GoChile)

Let me tell you this story of old. The organisms are hungry for nitrogen so they can make proteins and DNA. The tastiest way to eat nitrogen (ammonia) is served only by lighting strikes, and lighting doesn’t come as often as their desires. In a gruesome turn of events, organisms eat their own to satisfy their cravings. Then, some heroic life form accidentally develops an enzyme to eat nitrogen gas (which is super-abundant, so food for everybody!). The microbes are able to pass this gene to one another, like passing a gift, in a process known as horizontal gene transfer. The inventor’s gift, the DNA blueprint for the enzyme, benefitted not only their community but the world for eons to come. The macabre starvation scenes are substantially decreased. Nitrogen availability cleared the way for multicellular, eukaryotic and human life forms.

Fast forward to 1880 C.E. , where a German chemist, Hermann Hellriegel, realized how important nitrogen fixation was to all life. In the wake of his discovery, scientists find out about the enzyme that catalyzes the reduction of gaseous nitrogen to ammonia and named it nitrogenase. By using the gift of nitrogenases in the soil, humans are able to farm food much more efficiently. It makes the difference between leftovers of primordial soup and that defty Christmas dinner we cherish!

Hermann Hellriegel, 1831–1895, German chemist

Skipping time to the present day, we’ve found something puzzling about these nitrogenases. Oehlmann and Rebelein in Marburg, Germany, have looked at scientific reports from the past and showed that the enzyme isn’t just the single gift “nitrogenase”. Apart from nitrogen reduction, the enzyme catalyzes so many different chemical reactions that the authors made a separate table to list reactions this enzyme can perform – and their list is far from complete. 

Oehlmann goes into the chemistry of these enzymes, and describes how the magic of these machines is hidden in a rotating iron-sulfur rod. Any molecule with the right layout can take a ride, like a merry-go-round, and come out transformed.

Nitrogenase catalyzes lots of substrates into even more products with a rotating axle. created with BioRender.

The most interesting reaction performed by this billion-year-old machine is the reduction of CO2. This reaction yields e.g. methane, ethane, propane – words you might recognize as fuel. By both cleaning up the greenhouse gas CO2 and producing renewable fuel in one step, nitrogenase is a gift once again!


Link to the original post: Oehlmann, N.N. and Rebelein, J.G. (2021), The Conversion of Carbon Monoxide and Carbon Dioxide by Nitrogenases. ChemBioChem. https://doi.org/10.1002/cbic.202100453

Featured image: created with Biorender.com