We Are All Asgardians

The discovery of a microbe called Loki may change everything.

Posted May 17, 2019

Finally, those of us interested in both Norse religions and the evolution of humans have something to celebrate. Buried deep in the sea floor off the coast of Greenland (and where else could this story originate?) scientists found a colony of microbes that may rewrite the history of human origins. These pesky creatures were named after the Norse god Loki, Lokiarchaeota. When the DNA of these Loki were sequenced by a group of Swedish scientists, they discovered three additional relatives of Loki; the entire grouping was combined into a new phylum called Asgard. 

Why is this discovery important? The secrets locked within the DNA of Loki and his fellow  Asgardians may lead to an explanation for what is considered the one of the most fundamental questions about the biological leap from small simple single celled bacteria to the big complex, multi-compartmental cells, called eukaryotes, that are the basic building blocks of large multicellular animals such as worms, cats and humans. The excitement comes from the discovery that Loki contains DNA that belong to eukaryotes. This is very surprising because Loki is clearly not a eukaryote; it’s an archaea, which is considered one of the oldest and simplest forms of life on Earth.

The origin tale now being told around scientific campfires is that long ago the ancestors of the Asgard archaea regularly feasted on carbon-based molecules. The byproducts of their meals were discarded into their environment where their neighbors, the bacteria, could feed on them.

This beneficial food-sharing arrangement was taken to another level, about two billion years ago, when a Loki engulfed one of its bacterial neighbors and, quite surprisingly, the two lived happily ever after; the Loki consuming fatty acids while giving its indwelling bacterial lodger a safe and nutritious place to live. This new housing unit we now call a eukaryote and the bacteterial lodger eventually evolved into what is now called mitochondria. This highly efficient, large, carbon-consuming cell ultimately evolved into the building blocks for all complex, multicellular life, including humans. Recently, a group of scientists from the Czech Academy of Sciences captured a picture of one of these ancient Asgardians. They’re round. Stayed tuned for more pictures of our fellow Asgardians.  

Only Loki could appreciate, and possibly rejoice in, the consequences that were set in motion by these Asgardians. The mitochondria became the furnace that handles almost all of our cells’ energy production needs. They combine these leftover carbons with a readily available gas, oxygen, and to expel the product as a gas called carbon dioxide. Thus, thanks to our current symbiotic relationship with the descendants of these ancient bacteria, our mitochondria, the way our bodies obtain energy to live is as follows: Carbon bonds come into the front end of our feeding tubes in the form of fats, carbohydrates, and proteins; we then extract energy and excrete the residue as carbon dioxide and water vapor.

Because oxygen is also exceedingly toxic to cells, it must be used very carefully and conservatively. Indeed, scientists have recently discovered that the genes that control energy metabolism have been highly conserved across millions of years of evolution, from yeast to humans, and that these genes influence the rate of the aging process. Essentially, the better we negotiate our energy– oxygen exchange with our indwelling mitochondria, the longer and healthier we live as a single individual and as a species. Disrupt the balance in this exchange, and the impact can be harmful.

Because we insist on eating and breathing, tissue-damaging molecules called oxygen-free radicals are formed by our mitochondria. Free radicals are not always harmful, but they become more prevalent with age and may slowly overwhelm our natural antioxidant systems, destroying just about every cell in our bodies. Thus, the mitochondrial power plant that resides in quite large numbers in every cell of our bodies is actively injuring those cells by the very process of trying to keep them alive. It turns out that each species’ maximum life span may be determined by how many free radicals are produced by the hundreds of mitochondria that live in each of their cells. Loki, and his kin, made certain that the seeds of our demise live within each of us.

(c) Gary L. Wenk, Ph.D.

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