Algae that can fix nitrogen – thanks to a tiny cell structure | Hacker News Reader

Algae that can fix nitrogen – thanks to a tiny cell structure

nature.com

108 pointsrntn27 comments

Previously: https://news.ycombinator.com/item?id=40011438

The source paper: https://www.science.org/doi/10.1126/science.adk1075

Can anyone say whether it is possible to have an accident where this becomes a runaway process like the Great Oxidation Event?

https://en.m.wikipedia.org/wiki/The_Nitrogen_Fix

that was cool, thanks!

Just want to point out, the Great Oxidation Event took 400M years.

Once nitrogen is not a limiting factor for growth anymore, other elements will be, like phosphorus and sulphur.

Given that we're talking about eukaryotes here, you can't just sprinkle some modified DNA on it and expect it to start executing that code (like you can with bacteria, see https://en.wikipedia.org/wiki/Transformation_(genetics) ). So patching the organism with the code for the new organelle requires some kind of vector, like a virus or CRISPR. If such a thing were to be surprisingly widely applicable across species and also escape the lap, I suppose it could update more than just the desired plant.

Given that some other nutrient would then become the bottleneck, I think this would be ok though. You'd just have upgraded plant growth, which would mean locking carbon into biomass at an increased rate, which might be kinda helpful around now.

Would it have unintended consequences? Probably. Would they be worse than the unintended consequences of industry? Maybe not.

I suspect what stops this from being a universal feature of plants is the energy required to fix nitrogen. A plant is better off not trying to do that. Especially since if nitrogen is a limit then other nutrients are probably close behind.

I don't know, but if it was possible surely it would already have happened with the legumes?

> Can anyone say whether it is possible to have an accident where this becomes a runaway process like the Great Oxidation Event?

Probably not, due to denitrifying organisms [1]. The GOE occured because aerobic respiration, the biological balance to photosynthesis, didn't exist [2]. So when cyanobacteria began photosynthesising, the only counterbalance was ferrous iron dissolved into the oceans. Once that's reduced, that's it. No cycle. In contrast, more nitrogen fixation would prompt more denitrification, thereby balancing the system.

So to complete your disaster novel, you'd need to kill off denitrifying bacteria. Ironically, it appears they require "a very low oxygen concentration of less than 10%."

[1] https://en.wikipedia.org/wiki/Denitrification

[2] https://pubmed.ncbi.nlm.nih.gov/28360330/

[3] https://en.wikipedia.org/wiki/Oxygen_cycle

[dupe]

More discussion: https://news.ycombinator.com/item?id=40011438

Scientists tell us that when microbes started making O2, they changed Earth's atmosphere and triggered nass extinctions.

I wonder what consuming most of the N2 would do?

Well, if we could fix even a fraction of the Nitrogen, we could support a lot more plant life, that’s for sure! Oxygen is very reactive, Nitrogen, not so much. I don’t think the lack of Nitrogen would be very noticeable even if it dropped by half.

What would replace it? I'd expect a thinner atmosphere.

I'd expect the lack of anything that it is made to react with.

Mostly Nitrogen does not constrain growth in natural ecosystems. There are plenty of plants that fix nitrogen already, and nitrogen fixing plants would dominate an ecosystem if Nitrogen were a primary constraint on growth. There is plenty of Nitrogen available from the air - the main restriction is energy - the second restriction is that plants prefer to use most of their available energy on other things.

Nitrogen is important in fertilizer because our farming and agriculture is not a natural ecosystem.

> There are plenty of plants that fix nitrogen already, and nitrogen fixing plants would dominate an ecosystem if Nitrogen were a primary constraint on growth.

No plants can fix nitrogen. Hence this research?

You said this with such confidence I had to look this up, because I am quite familiar with the types of plants referred to as “nitrogen fixing plants” such as legumes. But here’s the answer for anyone else curious:

“Nitrogen fixing plants don't pull nitrogen from the air on their own. They actually need help from a common bacteria called Rhizobium. The bacteria infects legume plants such as peas and beans and uses the plant to help it draw nitrogen from the air. The bacteria converts this nitrogen gas and stores it in the roots of the plant.”

https://www.gardeningknowhow.com/garden-how-to/soil-fertiliz...

Thanks! Appreciate the reference. :)

> No plants can fix nitrogen

Plants fix nitrogen in common parlance but you are technically correct: I sincerely hope that your scientific pedantry works out better for you than it has for me (I won't delve into that topic further).

"Please respond to the strongest plausible interpretation of what someone says".

The research was specifically about introducing nitrogen-fixing organelles into plants because they have none. Precision is valuable since this was in direct contradiction to the original topic. Maybe common parlance is better-suited to a thread on vegetable gardening than microbiology.

If atmospheric nitrogen dropped by half, I'd imagine the effects would be pretty significant for aircraft, birds & internal combustion engines. Rocket launches would become more efficient (less drag), but reentry would be more challenging, w/ less overall drag & proportionally more oxidizing effect when aero-braking

Most engines would probably run hotter & weaker w/out as much nitrogen to use as a working fluid (maybe we'd compensate for this w/ water injection & get even better performance though?)

The speed of sound would decease slightly, while the speed needed to generate lift at a given altitude would increase. This would definitely affect airplanes, e.g. a plane that can cruise at 15k feet but not 30k feet might not be able to reach 15k feet anymore

Nitrogen is 77% of the atmosphere by weight.

For reference at 1 mile is Denver Colorado (which while researching is enough to cause altitude sickness) with 18% less atmosphere. Water boils at 200° F.

If half the nitrogen was gone (38.5% of atmosphere), sea level world be equivalent to ~15,000 feet today) water would now boil at ~194.3° F.

There have been several PhD theses on trying to fix nitrogen to grow wheat in the dessert. To my knowledge none have been successful.

Similarly interesting development: "green lightning" electricity + air + ammonium => ammonium nitrate fertilizer

source?

https://www.greenlightning.ag/

"$.04 per lb of N. $.70 per lb N is about standard currently for uan32" according to a random redditor (lost link, pulling from second-hand Signal chat history)

Appears to use this https://en.wikipedia.org/wiki/Birkeland%E2%80%93Eyde_process

Highly inefficient chemically, and produces salt nitrate, but energy is cheap enough it seems to beat out offsite transport

```

~250kg/ salt nitrate per ha ha farm feeds comfortably 10 ppl year round. 25kg salt per person/yr 12.5kg nitrate/person per year

60 g per kWh 1kWh/.06kg*12.5kg 208kWh/person/yr (less than 1 300W solar panel pp) estimate $0.1/kWh $20 e- per year per person best case

```

All I've got on it. Needs Potassium and Phosphorus supplements for ideal fertilizer still. Very neat though, and seemingly a sizable step economically - especially where fertilizer costs are the farming bottleneck. Can almost make self-contained plant + solar + water collection + harvesting bot + green lightning units that grow indefinitely without any inputs but air, rain and sun.

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