WEBVTT - How Does the Nitrogen Cycle Work?

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<v Speaker 1>Welcome to brain Stuff, a production of I Heart Radio. Hey,

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<v Speaker 1>brain Stuff, Lauren Vogel bomb here. Everybody needs nitrogen, but

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<v Speaker 1>as far as non negotiable life sustaining elements go, it's tricky.

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<v Speaker 1>Living things require nitrogen for their cells to function. And furthermore,

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<v Speaker 1>we're virtually steeping in the stuff since our atmosphere is

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<v Speaker 1>made up of seventy percent nitrogen gas. However, there's a catch.

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<v Speaker 1>It's a water water everywhere, but not a drop to

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<v Speaker 1>drink kind of situation. Although nitrogen is floating basically everywhere,

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<v Speaker 1>it's not terribly abundant in the Earth's crust, and it's

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<v Speaker 1>incredibly difficult for living things to capture atmospheric nitrogen and

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<v Speaker 1>use it for their purposes. It's like having a bucket

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<v Speaker 1>full of Icelandic money and say Minneapolis, where you can't

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<v Speaker 1>spend it. And we spoke by email with Jesse Moates,

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<v Speaker 1>a PhD candidate at the Odum School of Ecology at

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<v Speaker 1>the University of Georgia. She said nitrogen is a major

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<v Speaker 1>part of amino acids, which are the building blocks of

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<v Speaker 1>proteins and nucleic acids such as DNA. In addition to

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<v Speaker 1>needing nitrogen for proteins and plants. It's a main component

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<v Speaker 1>of chlorophyll, which makes it crucial for photosynthesis. Since nitrogen

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<v Speaker 1>is a limited resource on this planet, a nitrogen atom

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<v Speaker 1>doesn't spend much time doing nothing when it's in a

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<v Speaker 1>form that living things can use. Scientists called nitrogen in

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<v Speaker 1>this form fixed. A fixed nitrogen is taken up by plants,

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<v Speaker 1>which are eaten by animals, which eat other animals, which

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<v Speaker 1>die and decompose and release nitrogen back into the ecosystem

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<v Speaker 1>to be worked on by bacteria or plants. And this

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<v Speaker 1>is the cycle of a nitrogen atom on Earth, and

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<v Speaker 1>its journey starts either very quietly or with a humongous bang.

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<v Speaker 1>The step one in the cycle is nitrogen fixation. Believe

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<v Speaker 1>it or not, Lightning and bacteria are the two things

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<v Speaker 1>primarily responsible for turning atmospheric nitrogen into nitrogen that living

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<v Speaker 1>things can use. Atmosphere nitrogen is very stable, so it

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<v Speaker 1>takes an incredible amount of energy to convert it to

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<v Speaker 1>a different form. If you've ever wondered why your outdoor

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<v Speaker 1>plants seem happier after a thunderstorm than they do when

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<v Speaker 1>you turn a sprinkler on them, there's a reason for that.

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<v Speaker 1>Lightning electrifies atmospheric nitrogen and water to reconfigure them into

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<v Speaker 1>ammonia and nitrates. This falls to the ground is rain,

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<v Speaker 1>where plants slurp it up and use it for their

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<v Speaker 1>biological processes. On the other end of the spectrum, the

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<v Speaker 1>most common way nitrogen is made available to organisms is

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<v Speaker 1>when atmospheric nitrogen is fixed by bacteria, and some of

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<v Speaker 1>which live free in the soil, and others of which

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<v Speaker 1>enjoy a symbiotic relationship with certain plant species. Lagoons like peas, clover,

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<v Speaker 1>and peanuts have little nodules on their roots that attract

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<v Speaker 1>bacteria that convert stubborn atmospheric nitrogen into ammonia or ammonium,

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<v Speaker 1>which can then be used to power the plant. Step too,

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<v Speaker 1>is nitrification. Ammonia in the soil can be used directly

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<v Speaker 1>by plants, but it's all so a step in the

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<v Speaker 1>process of nitrification, through which specialized bacteria and other microorganisms

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<v Speaker 1>convert ammonia into nitrite and then pass it off to

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<v Speaker 1>an entirely different set of micro organisms that further oxidize

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<v Speaker 1>the nitrate into nitrate. This process is slow, but it's

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<v Speaker 1>the way that nitrogen is built as a nutrient. In

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<v Speaker 1>soil and aquatic and marine environments. Terrestrial plants, for instance,

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<v Speaker 1>can absorb ammonium and nitrate through their root hairs. The

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<v Speaker 1>organisms that specialize in nitrification are also important in treating

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<v Speaker 1>municipal wastewater, and anyone who's kept an aquarium knows how

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<v Speaker 1>important those organisms are to keeping your water, fish and

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<v Speaker 1>plant friendly. Step three is a monification. Everything living eventually

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<v Speaker 1>dies and the nitrogen a particular organism was using when

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<v Speaker 1>it shuffled off. This mortal coil is taken to hand

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<v Speaker 1>by bacteria that turned the nitrogen rich corpse into ammonium,

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<v Speaker 1>which can be picked back up by plants and used again.

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<v Speaker 1>The step four is D nitrification. It's possible to convert

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<v Speaker 1>bioavailable nitrogen into atmospheric nitrogen again, and that process is

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<v Speaker 1>called unitrification. Nitrification is performed by bacteria and other microorganisms

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<v Speaker 1>that can tolerate oxygen. Not all microorganisms can. In the

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<v Speaker 1>case of D nitrification, certain anaerobic bacteria that don't need

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<v Speaker 1>oxygen convert nitrate to nitrogen gas, which floats up into

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<v Speaker 1>the atmosphere and plays hard to get again until some

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<v Speaker 1>lightning or crafty bacterium comes along and ropes it. Back

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<v Speaker 1>into the first step of the nitrogen cycle yet again.

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<v Speaker 1>Today's episode was written by Justesceline Shields and produced by

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<v Speaker 1>Tyler Klang. For more on this and lots of other

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<v Speaker 1>cyclical topics, visit how stuff works dot com. Brain Stuff

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<v Speaker 1>is production of by Heart Radio. Or more podcasts to

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