
Cyborg bacteria outperform plants when turning sunlight into useful compounds - dnetesn
https://phys.org/news/2017-08-cyborg-bacteria-outperform-sunlight-compounds.html
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spqr0a1
This appears to be a based on a paper from last year.
[http://science.sciencemag.org/content/351/6268/74](http://science.sciencemag.org/content/351/6268/74)

While good and interesting work, there's a lot left to do. They're using
cysteine as a reductant, so not all of the energy is coming from light.
Furthermore while the system uses 90% of the cysteine and 80% of blue light,
it is only 2% efficient with broad spectrum (sun-like) lighting. Even that
well only under dim lighting.

Edit: Here's a group that's developed a system that's 5 times as efficient and
only uses CO2 and water as feedstock rather than cysteine and cadmium.
[http://science.sciencemag.org/content/352/6290/1210](http://science.sciencemag.org/content/352/6290/1210)

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subnaught
That's an apples-and-oranges comparison. The system you cite differs from the
one under discussion in several ways; the most important of which are:

1\. The cited system does not include a light-harvesting component. It merely
postulates that the required energy _could_ be generated from photovoltaics.
This would introduce additional cost and complexity along with an efficiency
hit.

2\. The cited system comprises a bacterium in conjuction with an electrode-
supported catalyst, whereas the system under discussion is solely an
engineered bacterium.

Finally, it is not correct to refer to cadmium and cysteine as feedstocks.
They are components of the catalyst, and they are not consumed during
catalysis. The only feedstocks for _both_ systems are CO2 and water.

~~~
spqr0a1
You're right that Liu's paper does use external electrodes. And as for
Sakimoto's paper it's true that the cadmium should be reusable indefinitely,
but if you read the second page it's clear than cysteine is consumed in
stoichiometric amounts. I'd be excited to hear about more recent work which
improves upon this and would be happy to be corrected.

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fpoling
Once more efficient capture of solar energy by single-cell organisms wiped out
probably 95% of life forms on Earth [1]. Have we learned the lesson?

[1] -
[http://www.slate.com/blogs/bad_astronomy/2014/07/28/the_grea...](http://www.slate.com/blogs/bad_astronomy/2014/07/28/the_great_oxygenation_event_the_earth_s_first_mass_extinction.html)

~~~
sqeaky
I wonder if these would do well in the wild? If so there is a huge ethical
issue here.

I think a more likely possibility is that they might be like like most
domesticated photosynthesizers. Loose populations would revert to more natural
traits and become less useful to humans and barely struggling for survival.

Consider what happens when farm grown tomatoes or corn go wild. The vast
majority die off because their fruit wastes a ton of energy becoming huge and
visually appealing. Those with just enough fruit to entice animals to spread
it, those that grow faster and those with the best resistances will succeed in
the wild.

Can these bacteria benefit from these solar cells without the help of humans
feeding them? If they could then natural selection will reinforce our
decisions and we could have a real threat.

I agree the risk reward part of this needs careful analysis, I don't think we
need to go straight to doom and gloom.

EDIT - Speeling, and grammar.

~~~
fpoling
[1] gives example how simple selection for better use in agriculture gives big
problems a few years later when the plant mutates in wild into a nasty pest.
Situation is especially sad in poor regions of Russia North where lack of
money in local budgets allowed the plant to spread everywhere. Driving there
is like watching illustration for "The Day of the Triffids" by John Wyndham
[2].

[1] -
[https://en.m.wikipedia.org/wiki/Heracleum_sosnowskyi](https://en.m.wikipedia.org/wiki/Heracleum_sosnowskyi)

[2] -
[https://en.m.wikipedia.org/wiki/The_Day_of_the_Triffids](https://en.m.wikipedia.org/wiki/The_Day_of_the_Triffids)

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emeijer
"The bacteria operate at an efficiency of more than 80 percent"

Really? If this technology is able to convert energy from sunlight + co2 into
carbon based fuels at 80% efficiency, that's quite astounding. Something like
that could solve the whole energy storage problem we have with solar and wind
energy. Almost sounds too good to be true.

~~~
digi_owl
The elephant, as always, is "will it scale?"...

~~~
tomjen3
It is bacteria. Those usually have no issue scaling.

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woliveirajr
> Upon addition of a simple Cd2+ salt and the sulfur amino acid cysteine, the
> non-photosynthetic Moorella thermoacetica self-photosensitizes through the
> synthesis of light absorbing CdS nanoparticles. This hybrid organism, M.
> thermoacetica-CdS, produces acetic acid from CO2, water, and light at
> quantum efficiencies above 80%.

One problem is that cadmium is toxic, highly toxic, so the removal of it
before refining any fuel will have to follow strict rules.

And wikipedia will have to be updated :)

> Although cadmium has no known biological function in higher organisms (...)

([https://en.wikipedia.org/wiki/Cadmium](https://en.wikipedia.org/wiki/Cadmium))

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jacobush
_Higher_ organisms.

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mattferderer
If you're as inept at Chemistry as I am, I highly suggest the video in the
article. I'm inept at Chemistry but this sounds fascinating. Here's my TLDR
summary of this article for others like me. Please correct me if I'm
misunderstanding it.

TLDR: A bacteria that can't photosynthesis sunlight is covered with
semiconductors that allow it to use the sunlight. The bacteria efficiently
produces an acid that can be turned into fuels, medicine, polymers & more. The
bacteria can regenerate & replicate as well so there is no waste.

What I don't understand is the regenerating & replicating part. I'm assuming
they take this bacteria & place the semiconductors on it. When it replicates,
does the new bacteria created have these semiconductors on it as well? If so,
how?

~~~
subnaught
You've got a lot of it right, but you're missing the key advance described
here, which--if true--is pretty wild.

Taking a step back, in 2016, this group did cover a bacterium with tiny
semiconductor nanoparticles (specifically CdS) just as you say. That work is
described here:
[http://www.pnas.org/content/113/42/11750.full](http://www.pnas.org/content/113/42/11750.full)
In short, the semiconductors act as mini-solar cells, converting light into
electrical current. The bacteria then use that electricity to convert CO2 into
acetic acid. That already is pretty cool.

However, what they claim now is that they don't even need to make the
semiconductor nanoparticles. They can simply grow the bacteria in an
environment containing cadmium and sulfur sources and the bacterium will
synthesize it's own cadmium sulfide coat, and use it for photosensitization.

This is really pretty wild. Bacteria will often incorporate various elements
from their host medium, but the generally use them to make biomolecules, not
semiconductors. Right now, this is just being presented at a conference, but
it will be very interesting to see the details when the full paper comes out.

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meri_dian
>"The hybrid organism, M. thermoacetica-CdS, produces acetic acid from CO2,
water and light."

I love bacterial and algal based approaches to fuel generation. Re-purposing
nature's own highly advanced (relative to our own state of the art) chemical
processing machinery seems an easier path forward than building our own from
scratch.

That said, relying on a fuel source that requires CO2 as input seems just as
potentially destabilizing to the global carbon cycle as relying on a fuel
source that produces CO2 as byproduct.

~~~
yorwba
> That said, relying on a fuel source that requires CO2 as input seems just as
> potentially destabilizing to the global carbon cycle as relying on a fuel
> source that produces CO2 as byproduct.

You mean like wood? Burning that fuel releases the same amount of CO2 back
into the atmosphere; the end-to-end process is carbon-neutral.

~~~
meri_dian
The end to end process of burning coal is also carbon-neutral according to
that logic, yet it seems to be causing some trouble.

~~~
adrianN
If you were a resident of Earth at the time where the coal deposits were
formed, you'd find our current climate pretty frigid. From your point of view
it would just be returning back to normal :)

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itchyjunk
When I see tech like this, I think of how this will help us colonize space
faster. But I wonder if there is a good scifi plot twist to be had when stuff
escapes the lab (here or in space). AKA, when is it appropriate to add the
weight of safety to research and experiments?

~~~
Retric
There is not really much Cadnium in the wild. Humans are made from Oxygen
(65%), Carbon (18.5%), Hydrogen(9.5%), Nitrogen (3.2%), Calcium (1.5%),
Phosphorus(1.0%), Potassium(0.4%), Sulfur (0.3%), Sodium(0.2%),
Chlorine(0.2%), Magnesium (0.1%) because they are reasonably plentiful. So
that's mostly what living things are made of. You get some things like iron in
hemoglobin, but iron is ~1/20,000th of a persons body weight and heavily
recycled. Yet, iron deficiency is still a common issue.

~~~
digi_owl
On that note, i recall hearing about an iron fish various health orgs have
been distributing in poorer nations.

This because as households switched out their old iron pots with modern ones,
there has been an uptick in deficiencies.

~~~
sp332
This one [http://www.luckyironfish.com/](http://www.luckyironfish.com/)
[https://en.wikipedia.org/wiki/Lucky_iron_fish](https://en.wikipedia.org/wiki/Lucky_iron_fish)

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pasta
So in the near future we might dump our trash into our cars for fuel [1].

[1]
[http://backtothefuture.wikia.com/wiki/Mr._Fusion](http://backtothefuture.wikia.com/wiki/Mr._Fusion)

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f09ui
The way the authors calculate the Quantum yield is by dividing estimated total
number of electrons to estimated total number of photons. If you do it the way
the plant and algae people do it(divide the total number of carbon to the
total number of photons), the quantum yield of photosynthesis is now 20% (in
plants and algae you can get to 10-11%).

Also, cysteine is used as a reductant - as soon as they will try to use water
as an electron donor the efficiencies will like ly to go down.

And who is going to count the energy needed for bacteria metabolism?!

