Is nitrogen, the building block of life, a latent time-bomb? Premium

Discover the fascinating world of nitrogen, from knuckle-cracking to agriculture, and the urgent need to address nitrous oxide emissions.

There’s a harmless addiction that many people share: knuckle-cracking. That ‘pop’, better than the one from squeezing bubble wrap, results from the synovial fluid between your joints releasing a small bubble of nitrogen when you twist or compress your fingers or toes. It’s also a reminder of the centrality of nitrogen to life. The fifth-most abundant gas in the universe, the most pervasive on earth, there is roughly three times more nitrogen in the air than oxygen. While it only constitutes a mere 3% of our body weight, life, without it, would be impossible.

NO, or nitric oxide, inside your body mediates the efficient transmission of messages among the nerves. It dilates arteries easing the flow of blood and improves immunity. Adenosine triphosphate (ATP), the fundamental currency of energy for cells, is part-constituted of nitrogen. Finally, the building blocks of DNA (deoxyribonuclease), the blueprint of life, are made up of four nitrogenous bases.

We can breathe in nitrogen but ironically cannot directly use a smidgen of it. The lungs – masters at extracting every molecule of oxygen from inhaled air to keep our cells alive – are flummoxed by nitrogen.

This is one of the reasons humanity and the rest of the animal kingdom depend on plants, who by the way are also inept at extracting nitrogen from the air. Via what could be described as The First Great Outsourcing, some plants were smart enough to form an alliance with certain ancient bacteria and archaea called ‘diazotrophs’.

Nearly 20,000 species of plants of the family Leguminosae – which include beans, chickpeas, lentils, soybeans, and peanuts – exist because of this symbiotic relationship between diazotrophs and them. The barter is that the former live on their nodules and break down nitrogen in the air into ammonia and ammonium, and the latter provide them a free supply of sugars. Nitrification is the process by which bacteria – that usually attach themselves to the root or live in the soil – turn the ammonia and ammonium into nitrites and nitrate.

That is the form a plant finally identifies as ‘useful’ and then goes on to make proteins, chlorophyll, their own proteins, and most other stuff necessary to their lives. These make their way into other animals and us. Plants that are non-leguminous – rice, wheat, maize for instance – must depend on diazotrophs in the soil.

Not all of the available nitrogen and the manufactured nitrate can be used and a large ecosystem of microbes exists to convert these nitrates back to nitrogen, called denitrification, and the cycle continues.