Thread by @mike_malaska

I learned something today in #astrobiology that just totally blew my mind.
There are microbes that eat....air. And can live on just....air.

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These microbes live in cold deserts...I mean really brutal cold deserts. Barren rocky ridges (not even tundra) in Antarctica.
There's really no free water - very dry. And dark for 6 months, too. So these microbes live where there isn't enough water for photosynthesis producers.

They live on the trace amounts hydrogen gas (H2) in the atmosphere (about 190 parts per BILLION), and CO (20 parts per BILLION). So these things are living on tiny tiny tiny amounts of stuff.
But...they are still living.

These bacterial communities have Actinobacteria. It's a big family, that includes some that can survive extreme environments like in ice. Here is a Wikipedia image of an Actinobacteria:
en.wikipedia.org/wiki/Actinobac…

These bacteria have a special modification of an enzyme called RuBisCO. RuBisCO is probably the most important enzyme on Earth. It is used to fix CO2 into sugars, when then is used to make everything else. (50% of leaf protein is RuBisCO) More here: en.wikipedia.org/wiki/RuBisCO

And if you want to get all hardcore and explore the enzyme structure in detail, check out the RCSB molecule-of-the-month on RuBisCO (structures 8RUC and 1RCX, hyperlinks in the text!):
pdb101.rcsb.org/motm/11

But these bacteria have modified versions of RuBisCO. They have a "type 1E" version, which when coupled up with hydrogenase enzymes (which they have) and carbon monoxide dehydgorenases (got that too.) let them eat that trace amount of hydrogen.
(Type 1E is not found in plants.)

So they get energy (and protons) from hydrogen. Then the carbon from CO and CO2. And along the way, the split oxygen and hydrogen makes water, so they really don't need extra water.
Oh, and community genetic analysis shows nitrogen fixation, too. So N2 in atmosphere gets used.

There is a great diagram in the discovery article by Li et al., Nature (2017), it's open-access so check it out:
nature.com/articles/natur…

Totally check out Figure 4 on the third page. Basically "air" --> "biostuff"

HOW TOTALLY AWESOME IS THAT????!!!!!

So these microbes don't need organics or sunlight to do their stuff. Just a few trace soil elements that aren't carbon, oxygen, nitrogen, an hydrogen - they get those elements and energy from THE AIR!!!!

So...the mindblowing bit is now you can imagine just those trace basic things H2, CO, CO2 in the deep subsurface ocean of an Ocean World. And that is just enough for these microbes to survive, get energy, nutrients, and most stuff they need to build bodies and reproduce.

And....now me going wild. If you don't need a lot of surface stuff, and can live on just air. Can you now imagine a biology that only lives in the clouds?

And this is where I tease y'all, (no patreon or anything), but the next seminar series for the Network of Ocean Worlds (@Ocean_Worlds) will feature Dr. David J. Smith of NASA Ames who will be talking about microbial life in Earth's stratosphere.
nasa.gov/ames/research/…

(and no, that hadn't officially been announced yet. And yes, I just let the cat out of the bag. And yes, they will be announcing just as soon as I send the email saying the speakers accepted to present. We will also feature Prof. Juan Lora of Yale talking about Titan atmosphere.)

So the whole atmosphere coupling to the cryosphere is a big deal and it is just AMAZING how the limits of life get stretched every time we explore.
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Gahhhh! Forgot! Here is a link to the Network for Ocean Worlds seminar series website. We've got the first three seminars already there (hosted on YouTube) so you can watch at your leisure.
oceanworlds.space/now-seminars/