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Mar 2 • 12 tweets • 4 min read
Let's talk about radiotrophic fungi.

I want to start with the most surprising fact about them: they don't just SURVIVE in high radiation environments, they grow at *FOUR TIMES* the rate they would in background radiation.

Our best guess is they're "eating" radiation.
The key is melanin, similar to the melanin that darkens your skin & protects you from UV damage. It's a dark, high molecular weight pigment polymer, absorbing 99.9% of UV & visible light.
Ionizing radiation beyond UV can change the electronic/chemical structure of melanin, making it act similar to chlorophyll in its ability to capture photons and generate electron gradients.

SOURCE: ncbi.nlm.nih.gov/pmc/articles/P…
Given these electron gradients and a carbon source, the fungi can synthesize basic nutrients, or metabolize environmental nutrients at a greater rate.
In 1986, dark, melanin-producing (melanotic) fungi were found on the walls of the Chernobyl reactor & in the cooling tower water. Samples of these fungi, when exposed to a radiation source, were observed to grow TOWARDS the source, along a gradient of increasing gamma exposure.
Other melanotic fungi have been found growing freely on Mir and ISS space stations, where radiation limits human habitation length.
They're also found in the mountains of Antarctica, suggesting the melanin is providing protection from cold or desiccation or simply the unshielded UV exposure of the South Polar region.
Space colonization might well benefit from a radiation shield that can be grown on other worlds from regolith and ionizing radiation, or protect travelers in transit.
A 3 in (9 cm) layer of Martian regolith colonized by these fungi would effectively absorb most or all of the damaging radiation at the Martian surface.

All of this is hypothetical, of course, but certainly piques my curiosity.
Some interesting sources to start your own exploration:
"Ionizing Radiation: how fungi cope, adapt, and exploit with the help of melanin"
Curr Opin Microbiol. 2008 Dec; 11(6): 525–531.
ncbi.nlm.nih.gov/pmc/articles/P…
"Chernobyl mold could shield astronauts from deep-space radiation"
engadget.com/international-…
"Fungi and ionizing radiation from radionuclides"
FEMS Microbiol Lett. 2008 Apr;281(2):109-20.
academic.oup.com/femsle/article…

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More from @c0nc0rdance

c0nc0rdance Profile picture
Mar 1
It's the last day of #BlackHistoryMonth, let's talk about Ernest Everett Just.

Just's story weaves together good, rigorous science with racism & tragedy.

He was born in 1883 in seaside Charleston, South Carolina.
By age 4, his father & grandfather had died, leaving his teacher mother to raise him & 4 siblings.

At a young age, he was sick w typhoid for 6 weeks. Afterwards, because of resulting brain damage, he had to re-learn how to read & write.
At 16, his mother sent him to a 4 yr prep school in New Hampshire, then she died the following year. He finished in 3 years with the highest grades in the class.
Read 16 tweets
c0nc0rdance Profile picture
Feb 23
In 2018, "Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial" was published in the British Medical Journal.

It sought to determine if wearing a parachute when jumping from a plane had any impact on survivability.

It did not. Image
The study was tongue in cheek to prove a point.

What is easy to miss is that the "tested population" were descending approximately 0.6 m (2 ft) from a plane traveling at 0 m/s.

Wearing a parachute turned out not to prevent any death or injury in either group. Image
The point being made is that randomized control trials have limitations: equipoise, for one, where
all groups need to have equal opportunity for good outcomes.

In this study, that means jumping 0.6 m from an immobile plane. Image
Read 8 tweets
c0nc0rdance Profile picture
Feb 23
If you had visited Texas 2 million years ago, you might have encountered Titanis walleri, the Phorusrhacid or "terror bird".

These 7 ft tall, 330 lb flightless predators could run up to 30 mph, had long talons and an axe-like beak they used to beat prey to death. A savannah or prairie scene with a large ostrich-like bird w
They hunted smaller mammals primarily, but were capable of killing even larger prey with their beaks.

The Turkey's Revenge!
Titanis walleri fossils have been found in Florida and Texas, but we don't know enough of their behavior from limited sampling. Based on bone groupings, we think they hunted in packs.

Here two Titanis attack a glyptodont, an armored mammals related to modern armadillos.
Read 5 tweets
c0nc0rdance Profile picture
Feb 22
Let's talk about what 'oakum' is & how it shaped society & medicine.

Oakum is from Middle English "okome", which means "off-combing". It's made by unraveling pine-tar coated nautical rope made of hemp or flax fibers.

The work was often done in jails, workhouses, sanitariums.
Oakum was the space-filler and sealant of its time, used in sealing cracks in everything from ships to log cabins to cast iron pipes.

Combined with hot tar, molten lead, or pitch, it absorbed liquids & the space-filling fibers swelled.
Making it was painful, repetitive, but pain-staking work. The raw material was cheap, the finished product sold for good profit. The work could be done by the infirm or elderly.

Bleeding fingers marked the oakum "picker".
Read 6 tweets
c0nc0rdance Profile picture
Feb 22
Climbing a tree to escape a bear is a plan with one really fatal flaw:
Bears ascend trees with incredible speed, owing to a number of adaptations to their musculoskeletal system that make them exceptional climbers.
Long curved claws (more curved in black bears, less so in grizzlies) & extremely powerful limb musculature allow for grip & lift climbing.

Unlike cats, with more curved claws & weak front limbs make them good at going up, but bad at going down, bears shimmy both up & down fast.
Black bears have been observed to use limb bundles to go out on branches we would judge too weak to support our weight.

Here the size & strength of the animal work to its advantage.
Read 4 tweets
c0nc0rdance Profile picture
Jan 2
Monozygotic ("identical") twins are NOT genetically identical, a fact that has both challenged historical twin studies on heritability of traits and also represents an opportunity for better insights.

So why aren't identical twins genetically identical?
Let's start with basics: one egg, one sperm, but at some point, the embryo splits or 'twins', and some of the embryonic cells go to each new cell mass.

Those divisions occur in cells that already differ.

Wild but true fact: Identical twins can be different genetic sexes!
Take this case where the twinning event occurred in an embryonic cluster that had a karyotype of 47,XXY (2 X, 1 Y per genome) where the X chrom was lost in one twin, and the Y chrom in the other.

Producing monozygotic 46;XX and 46;XY offspring.
pubmed.ncbi.nlm.nih.gov/18567067/
Read 13 tweets

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