Eukaryogenesis and oxygen in the biosphere

[RonO]

https://www.nature.com/articles/s41559-022-01733-y

https://www.exeter.ac.uk/news/research/title_909348_en.html

The second link is a news release on the research that is open access.
You have to pay to get access to the nature and ecology article.

Abstract
The endosymbiotic origin of mitochondria during eukaryogenesis has long
been viewed as an adaptive response to the oxygenation of Earth’s
surface environment, presuming a fundamentally aerobic lifestyle for the
free-living bacterial ancestors of mitochondria. This oxygen-centric
view has been robustly challenged by recent advances in the Earth and
life sciences. While the permanent oxygenation of the atmosphere above
trace concentrations is now thought to have occurred 2.2 billion years
ago, large parts of the deep ocean remained anoxic until less than 0.5
billion years ago. Neither fossils nor molecular clocks correlate the
origin of mitochondria, or eukaryogenesis more broadly, to either of
these planetary redox transitions. Instead, mitochondria-bearing
eukaryotes are consistently dated to between these two oxygenation
events, during an interval of pervasive deep-sea anoxia and variable
surface-water oxygenation. The discovery and cultivation of the Asgard
archaea has reinforced metabolic evidence that eukaryogenesis was
initially mediated by syntrophic H2 exchange between an archaeal host
and an α-proteobacterial symbiont living under anoxia. Together, these
results temporally, spatially and metabolically decouple the earliest
stages of eukaryogenesis from the oxygen content of the surface ocean
and atmosphere. Rather than reflecting the ancestral metabolic state,
obligate aerobiosis in eukaryotes is most probably derived, having only
become globally widespread over the past 1 billion years as atmospheric
oxygen approached modern levels.


Eukaryotes evolved from Archaeal bacterial ancestors, and the first
proto eukaryotes were anaerobic. Part of eukaryotenesis (development of
nuclei and mitochondria) are thought to involve endosymbiosis, so this
Archaeal ancestor was engulfing other bacteria. Mitochondria are
derived from eubacteria so part of it was a union of the two types of
bacteria that existed at the time. The eubacterial adaptation to oxygen
would have already occurred before the endosymbiotic relationship began.
These guys are claiming that there were anoxic regions on earth where
the endosymbiosis with these alpha proteobacteria could have occurred
with our anaerobic archaeal ancestor. This would have equipped early
eukaryotes with the ability to adapt to higher levels of oxygen in the
atmosphere and oceans.

Ron Okimoto

[Glenn]

On Sunday, May 1, 2022 at 5:31:02 AM UTC-7, Ron O wrote:
> https://www.nature.com/articles/s41559-022-01733-y
>
https://uncommondescent.com/intelligent-design/claim-complex-cells-started-without-oxygen/

[RonO]

The uncommonly dense are worse off than you, but you likely understand
that already. Probably why you go there for IDiocy. Misery must love
company.

Do you have any idea why having early eukaryotes (before they had
mitochondria) be anaerobic and have to live in an anoxic environment?
Where is the support for intelligent design? Why wouldn't the designer
just have eukaryotes be aerobic from the beginning of their existence?
Why would the designer need to make eukaryotes using anaerobic Archaeal
bacteria, and then have them join up with a different kind of bacteria
to give them the ability to use oxygen?

Ron Okimoto

[jillery]

On Sun, 1 May 2022 10:26:32 -0700 (PDT), Glenn <GlennS...@msn.com>
wrote:

>On Sunday, May 1, 2022 at 5:31:02 AM UTC-7, Ron O wrote:
>> https://www.nature.com/articles/s41559-022-01733-y
>>
>https://uncommondescent.com/intelligent-design/claim-complex-cells-started-without-oxygen/

A seven-line column, with one line devoted to mindless snark, and
making no explicit point at all.

Let's assume the cited paper is correct, and the previous consensus is
wrong. So what? It doesn't disprove evolution or support ID.

A reasonable inference is that the author is gloating over the fact
that science has to change it's mind... AGAIN!

Do you, Glenn, think science should ignore new evidence, or continue
to assert old ideas despite new evidence? I bet even you know of
organizations which do exactly that.

--
You're entitled to your own opinions.
You're not entitled to your own facts.

[jillery]

On Sun, 1 May 2022 07:27:39 -0500, RonO <roki...@cox.net> wrote:

>https://www.nature.com/articles/s41559-022-01733-y
>
>https://www.exeter.ac.uk/news/research/title_909348_en.html
>
>The second link is a news release on the research that is open access.
>You have to pay to get access to the nature and ecology article.
>
>Abstract
>The endosymbiotic origin of mitochondria during eukaryogenesis has long
>been viewed as an adaptive response to the oxygenation of Earth’s
>surface environment, presuming a fundamentally aerobic lifestyle for the
>free-living bacterial ancestors of mitochondria. This oxygen-centric
>view has been robustly challenged by recent advances in the Earth and
>life sciences. While the permanent oxygenation of the atmosphere above
>trace concentrations is now thought to have occurred 2.2 billion years
>ago, large parts of the deep ocean remained anoxic until less than 0.5
>billion years ago. Neither fossils nor molecular clocks correlate the
>origin of mitochondria, or eukaryogenesis more broadly, to either of
>these planetary redox transitions. Instead, mitochondria-bearing
>eukaryotes are consistently dated to between these two oxygenation
>events, during an interval of pervasive deep-sea anoxia and variable
>surface-water oxygenation. The discovery and cultivation of the Asgard
>archaea has reinforced metabolic evidence that eukaryogenesis was
>initially mediated by syntrophic H2 exchange between an archaeal host

>and an ?-proteobacterial symbiont living under anoxia. Together, these

>results temporally, spatially and metabolically decouple the earliest
>stages of eukaryogenesis from the oxygen content of the surface ocean
>and atmosphere. Rather than reflecting the ancestral metabolic state,
>obligate aerobiosis in eukaryotes is most probably derived, having only
>become globally widespread over the past 1 billion years as atmospheric
>oxygen approached modern levels.
>
>
>Eukaryotes evolved from Archaeal bacterial ancestors, and the first
>proto eukaryotes were anaerobic. Part of eukaryotenesis (development of
>nuclei and mitochondria) are thought to involve endosymbiosis, so this
>Archaeal ancestor was engulfing other bacteria. Mitochondria are
>derived from eubacteria so part of it was a union of the two types of
>bacteria that existed at the time. The eubacterial adaptation to oxygen
>would have already occurred before the endosymbiotic relationship began.
> These guys are claiming that there were anoxic regions on earth where
>the endosymbiosis with these alpha proteobacteria could have occurred
>with our anaerobic archaeal ancestor. This would have equipped early
>eukaryotes with the ability to adapt to higher levels of oxygen in the
>atmosphere and oceans.
>
>Ron Okimoto

Nick Lane wrote a book which suggested that oxygen produced from
ancient stromatolites was consumed almost completely within the
stromatolites. If so, it's plausible that early eukaryotes were
restricted to close symbiotic relationships within stromatolite
communities, and only later spread to other environments as oxygen
became more widely distributed from photosynthetic bacteria.

[Glenn]

On Sunday, May 1, 2022 at 3:16:03 PM UTC-7, Ron O wrote:
> On 5/1/2022 12:26 PM, Glenn wrote:
> > On Sunday, May 1, 2022 at 5:31:02 AM UTC-7, Ron O wrote:
> >> https://www.nature.com/articles/s41559-022-01733-y
> >>
> > https://uncommondescent.com/intelligent-design/claim-complex-cells-started-without-oxygen/
> >
> The uncommonly dense are worse off than you, but you likely understand
> that already. Probably why you go there for IDiocy. Misery must love
> company.
>

"This oxygen-centric view has been robustly challenged by recent advances in the Earth and life sciences."

https://www.nature.com/articles/s41559-022-01733-y

Earth sciences?

[jillery]

On Mon, 2 May 2022 00:13:11 -0700 (PDT), Glenn <GlennS...@msn.com>

wrote:

>On Sunday, May 1, 2022 at 3:16:03 PM UTC-7, Ron O wrote:
>> On 5/1/2022 12:26 PM, Glenn wrote:
>> > On Sunday, May 1, 2022 at 5:31:02 AM UTC-7, Ron O wrote:
>> >> https://www.nature.com/articles/s41559-022-01733-y
>> >>
>> > https://uncommondescent.com/intelligent-design/claim-complex-cells-started-without-oxygen/
>> >
>> The uncommonly dense are worse off than you, but you likely understand
>> that already. Probably why you go there for IDiocy. Misery must love
>> company.
>>
>"This oxygen-centric view has been robustly challenged by recent advances in the Earth and life sciences."
>
>https://www.nature.com/articles/s41559-022-01733-y
>
>Earth sciences?

"views" are routinely challenged in science. What is it about the
oxygen-centric view in particular that has your knickers in a twist?

[RonO]

Run, what good does it ever do for you?

REPOST:

The uncommonly dense are worse off than you, but you likely understand
that already. Probably why you go there for IDiocy. Misery must love
company.

Do you have any idea why having early eukaryotes (before they had
mitochondria) be anaerobic and have to live in an anoxic environment?
Where is the support for intelligent design? Why wouldn't the designer
just have eukaryotes be aerobic from the beginning of their existence?
Why would the designer need to make eukaryotes using anaerobic Archaeal
bacteria, and then have them join up with a different kind of bacteria
to give them the ability to use oxygen?

END REPOST:

You obviously don't want to understand either paper. My reference that
initiated this thread was claiming that oxygen levels didn't matter when
eukaryotes were evolving because there were anoxic environments on earth
just like today. That is how aerobic proteobacteria could evolve after
oxygen photosynthesis evolved and oxygen became an issue. The
proteobacteria that evolved aerobic metabolism evolved from anaerobic
bacteria, and would be expected to be able to exist in anaerobic and
aerobic environments just like the aerobic bacteria that exist today
that have the same ox phos system that our mitochondria have.

Ron Okimoto

[RonO]

It may have taken a long time before oxidative phosphorylation evolved.
Oxygen was toxic to life when it was first being produced. The first
oxygen producing photosynthetic organisms had to evolve defense against
the oxygen, and were likely expelling it as fast as they could. This
thread was about eukaryogenesis and we don't know if mitochondria
(bacteria that could use oxygen) or the bacteria that gave eukaryotes
photosynthetic ability were the first endosymbionts for the eukaryotic
lineage that became plants, but my guess is that eukaryotes first
developed a relationship with the bacteria that became our mitochondria,
and got initial defenses against oxygen from them and evolved their own
oxygen defense as they ventured out into more oxygen rich environments.
It would have been after they could tolerate oxygen that they engulfed
the chloroplastic bacteria that would fill them with oxygen.

It may have been that the chemistry of the water that they lived in
would have precipitated out the oxygen as soon as it was expelled and
this would have probably accumulated becoming part of the stromatolite.
There would likely be large amounts of Ferric oxide, or some other
oxidized compound in early stromatolites that were producing oxygen.

Ron Okimoto

[jillery]

IIUC there were anoxygenic photosynthetic bacteria producing molecular
sulfur before there were oxygenic photosynthetic bacteria producing
molecular oxygen.

According to Wikipedia, green sulfur bacteria, red and green
filamentous phototrophs, purple bacteria, acidobacteriota, and
heliobacteria all exist today. They use pigments other than
chlorophyll to capture light energy to reduce H2S to capture electrons
to produce ATP and NADPH to drive the same Calvin cycle as in all
photosynthetic organisms that reduces CO2 to produce glucose. This
suggests to me these two different phothosynthetic pathways evolved
from a common ancestor.

Similarly, there were anaerobic sulfur- and sulfate-reducing bacteria
before there were aerobic oxygen-reducing bacteria. So there are
plausible natural pathways for stromatolite communities to be
compatible with both anaerobic and aerobic environments.