The metagenome of the Christmas tree


The metagenome of the Christmas tree

The Christmas tree became common in Finland during the 19th century in estate homes. It is usually kept inside and is a decorated wild spruce (Picea). Along with the spruce, millions of wrappers, campers, glaciers, mites and spiders are carried home from nature. Spruce smells as it evaporates resinous organic substances such as phenols and other polyaromatic hydrocarbons. They can cause allergies, but bugs are essentially no harm. Are they actually useful?

A few years ago, I was overwhelmed as I learned how much genetic information content there is in the microorganisms of the environment, in the microbiome, or more precisely in its metagenome. Metagenomics studies the genomes of microscopic life forms and their interactions with each other and with larger organisms. It is a relatively new discipline born in the early 2000s. Bacteria and viruses are the number one research subjects in metagenomics.

The home has its own metagenome. Carrying spruce into the room with its bugs changes the metagenome of the home.

Home metagenomics are also shaped by family members, pets, plants, and other factors such as the location of the residence. Finns know that a summer cottage starts to change quickly if you don't actively visit it. Some houses even have their own characteristic smell on their own that can grow spontaneously stronger. If the house has been empty for years, it is not a good thing for the house. This is due to changes in the house and the metagenome that lives there.

Man modifies his environment to suit himself through his own actions, including its metagenomes. The people who live and work in the house thus affect the dynamics of the home on a large and small level, including the carried Christmas tree and its bugs. It may be that the cottage misses people and the Christmas tree as much as the people who gather around it, because otherwise the living space can start to be occupied by a hostile mushroom, for example.

Humans have bacteria and viruses and other microorganisms everywhere in the eyes, nose, skin, lungs, saliva, intestines. There are only maybe a kilogram of these in physical mass, but analyzing the genomes reveals that their diversity is mind-boggling.

The genetic information content of the human self is currently known to be 4,537,931,177 base pairs (ACGT) encoding 20,448 genes. All human cell types can be constructed from this information. The genetic information content of the human metagenome, including all the different germs and their variants, is hundreds of times greater. It contains thousands of species and millions of genes of which currently only 140,988 are known, according to open scientific databases. These construct numerically approximately the same number of cells as there are cells in the human body itself.

Spruce has 20 billion base pairs in its genome, five times more than humans. Very precise information on the number of spruce genes is not yet available. Spruce interacts with their metagenomes, sticking in place, and cannot, for example, try to develop vaccines if a harmful microorganism, pathogen, appears in the body.

It can be safely assumed that a microbiome living with an organism has, in principle, protective effects against the host. Their survival depends on the survival of the host entity. But this thing is still very poorly known.

The Earth's microbiome, or the entire microscopic organisms, have had the same amount of time in evolution as the macroscopic organisms. A common ancestor to these forms of life emerged billions of years ago. Since then, organisms have reacted to their environment in different ways in their own habitats and specialize in surviving in them. The interaction of life forms persists throughout the history of the earth.

It’s a good policy to assume for Christmas: to defend people and societies against pathogens, in co-evolution with the Christmas tree and its metagenome. This is what I was thinking when I brought inside our house. Spruce and its bugs and their metagenome are welcome to shape the health of our home!

Merry Christmas from the Finnish node of the European biological information infrastructure ELIXIR.

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Tommi Nyrönen

Dr. Tommi Nyrönen leads a team of experts in the European Life Science Infrastructure for Biological information ELIXIR at CSC.