Earth’s big fix is in the bacteria

Earth’s big fix is in the bacteria

Photo by Sourabh Panari on Unsplash

Originally published 25 April 2000

It’s plant­i­ng time. Rototill­ing. Hoe­ing. Stick­ing in the seeds. Onions. Radish­es. Let­tuce. Beans. No real need to do it. We can buy our veg­gies at the store for a lot less mon­ey than we send to Smith & Hawken for all those upscale gar­den tools.

But mon­ey’s not the point, is it? What’s real­ly going on here is a love affair with seeds, with the soil, with the sweet tac­tile plea­sures of snap­ping a sug­ar pea or hold­ing a hefty home­grown toma­to in the hand.

The veg­etable gar­den is our annu­al homage to the leafy green things we can­not do without.

Let me explain.

My 165-pound body con­sists of about 16 pounds of hydro­gen, 110 pounds of oxy­gen, 30 pounds of car­bon, 6 pounds of nitro­gen, and 3 pounds of every­thing else. Basic stuff, most­ly. The stuff of water and air. You’d think we could get almost every­thing we need by tak­ing a deep breath and a sip of water.

But it’s not that sim­ple. Con­sid­er, for a moment, those 6 pounds of nitro­gen in my body.

Nitro­gen is an essen­tial ingre­di­ent of pro­teins. About 30 pounds of me is pro­teins — tis­sue, bone, car­ti­lage, hair, enzymes, pro­tein hor­mones, and a diverse host of oth­er key parts and prod­ucts. Our cells build pro­teins by string­ing togeth­er 20 dif­fer­ent kinds of small­er chem­i­cal units called amino acids, and every amino acid con­tains a nitro­gen atom.

We need nitro­gen to make pro­teins. So what’s the prob­lem? The atmos­phere is 80 per­cent nitro­gen. We suck in a lung­ful of nitro­gen with every breath.

But the nitro­gen in the atmos­phere (and in our lungs) is use­less. The two nitro­gen atoms in a nitro­gen gas mol­e­cule are bound togeth­er so tight­ly that they are essen­tial­ly inert; they hard­ly react with any­thing else. We live in a sea of nitro­gen, and it does us not a bit of good. At least not directly.

To build amino acids, we need to get nitro­gen as part of organ­ic mol­e­cules from the food we eat — from oth­er ani­mals and plants. Even then, there are 10 amino acids that we can’t man­u­fac­ture our­selves — the so-called essen­tial amino acids — and for these we must rely on plants, which alone have the abil­i­ty to make all 20 kinds of amino acids. With­out plants — with­out those essen­tial amino acids — we’re up a creek with­out a paddle.

And where do the plants get their nitro­gen? Some is recy­cled from dead plants and ani­mals. Microbes in the soil break down dead tis­sue into nitrate and ammo­nia, which can then be used by plants. But the microbes also release some nitro­gen gas to the atmos­phere, where it is lost. Soon­er or lat­er, the whole process would come to a screech­ing halt as all the nitro­gen in the soil end­ed up as inert atmos­pher­ic gas.

And now the won­der­ful thing.

Bac­te­ria that live in con­junc­tion with cer­tain plants have the abil­i­ty to do what we can’t do and what plants can’t do: Take nitro­gen gas from the atmos­phere, break those dev­il­ish bonds, and turn the nitro­gen into a use­ful form that plants can use. This process is called “nitro­gen fix­a­tion.”

It’s a hap­py alliance. The bac­te­ria have an ener­gy source in the pho­to­syn­the­siz­ing plants. The plants get use­ful nitrogen.

So, ulti­mate­ly, the whole grand pageant of life on Earth depends on nitro­gen-fix­ing bac­te­ria that live in or around the roots of plants. My 6 pounds of nitro­gen was sequestered from the air by invis­i­ble bugs.

Well, maybe not all of it. In 1909, a Ger­man chemist named Fritz Haber invent­ed a way to use high tem­per­a­tures and pres­sures in the pres­ence of a cat­a­lyst to make atmos­pher­ic nitro­gen react with hydro­gen to form ammo­nia — arti­fi­cial fer­til­iz­er for agriculture.

Of course, arti­fi­cial fer­til­iz­er has prob­lems of its own — run-off of excess nitrates from fields poi­sons lakes and streams — but it all comes down to the melan­choly fact that we have made so many of our­selves that the human need for food far out­strips the abil­i­ty of bac­te­ria to sup­ply us with nitro­gen. Almost all the fixed nitro­gen in the fields of Egypt, Indone­sia, and Chi­na comes from syn­thet­ic fer­til­iz­er — 100 mil­lion tons of it a year. If it weren’t for the Haber process, lots of folks would be starving.

Or to put it anoth­er way, if it weren’t for the Haber process, there would­n’t be so many of us.

In our back­yard gar­dens, these glob­al prob­lems of feed­ing the bil­lions can be bliss­ful­ly ignored. Instead, we plunge our hands into the warm­ing soil and cel­e­brate a delight­ful inti­ma­cy with the ancient mir­a­cle of sun, seed, leaf, root — and those unseen but indis­pens­able nitro­gen-fix­ing bac­te­ria that make it all possible.

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