On 6/9/21 3:04 PM, erik simpson wrote:
> On Wednesday, June 9, 2021 at 2:22:54 PM UTC-7, Peter Nyikos wrote:
>> On Tuesday, June 8, 2021 at 11:30:08 AM UTC-4, erik simpson wrote:
>>> On Tuesday, June 8, 2021 at 8:00:29 AM UTC-7, nyik...@gmail.com wrote:
>>>> On Wednesday, June 2, 2021 at 7:13:58 PM UTC-4, erik simpson wrote:
>>>>> On Wednesday, June 2, 2021 at 3:01:16 PM UTC-7, Peter Nyikos wrote:
>>>>>> On Tuesday, June 1, 2021 at 8:04:07 PM UTC-4, erik simpson wrote:
>>
>>>>>>> Here's the most recent comprehensive review of Cyanobacteria
fossils:
>>>>>>>
>>>>>>>
https://www.sciencedirect.com/science/article/pii/S0891584918324845?via%3Dihub
>>>>>> Cyanobacteria evolution: Insight from the fossil record
>>>>>> Catherine F.Demoulin, Yannick J.Lara, Luc Cornet,
CamilleFrançois, DenisBaurain, AnnickWilmotte, Emmanuelle J.Javaux,
>>>>>> Free Radical Biology and Medicine Volume 140, 20 August 2019,
Pages 206-223
>>>>>>
>>>>>> Thank you very much, Erik. It does look like a very valuable
resource on the subject.
>>
>>>>>>> Chemical remains are important information, but peptidoglycan
(mentioned in the review) isn't discussed as
>>>>>>> present in the fossils (no surprise there).
>>>>>>>
>>>>>>> I haven't read all of it yet, but I intend to. Considerable
info is new to me.
>>
>>>>>> For me too. A quick skim fails to provide answers to the two
questions that interest me most at the present time:
>>>>>> (1) are cyanobacteria fossils from a billion or more years ago
exclusively from stromatolites and
>>>>>> (2) are they all thick-walled?
>>>>>>
>>>>>>
>>>>>> I'll be looking at it off and on for about a week before posting
on it. Mostly off: for the better part
>>>>>> of this past academic year, my family has had to ration their
time with me due to the tremendous burden
>>>>>> of online teaching -- almost three times as time-consuming as
in-person teaching. I've decided to give
>>>>>> them some real quality and quantity time, so I'm going on a
posting break until next Tuesday.
>>>>>>
>>>>>> Meanwhile, here's something y'all might think about: how rare is
it to have fossils of any organisms which,
>>>>>> like *Bicellum* *brasieri,* are from a billion or more years ago
and are NOT from stromatolites?
>>>>>>
>>>>>>
>>>>> I believe most of the cyanobacterial fossils are derived from
stromatolites, but some are found in other
>>>>> "microbially induced sedimentary structures (MISS)".
>>>>>
>>>>> Unsheathed cyanobacteria are known in the fossil record, but the
majority of fossils are thick-walled, probably
>>>>> due to tophonomy favoring the thick-walled specimens.
>>
>>>> There is also what might be called "identification bias": there
are lots of different microorganisms in
>>>> stromatolites, but the article you showed us judges whether a
microorganism is a cyanobacterium
>>>> based on its resemblance to extant cyanobacteria.
>>>>
>>>>
https://www.sciencedirect.com/science/article/pii/S0891584918324845?via%3Dihub
>>>>
>>>> Its criteria are sufficiently stringent so that "only three taxa
are unambiguously identified as cyanobacteria." [p. 209] Earlier on that
page we see:
>>>>
>>>> "In this section, we discuss a selection of (1) unambiguous
cyanobacteria microfossils for which morphological features and habitats
coincide strikingly with modern lineages, (2) probable and possible
cyanobacteria microfossils that share morphological similarities both
with a taxon belonging to the cyanobacterial phylum and with other
lineages belonging to another phylum or domain of life. The limited
number of preservable characters, along with their taphonomic
alteration, and possible morphological convergence, limits the
interpretation of the fossil record."
>>>>
>>>> Criteria like these can also be responsible for putting the "first
known cyanobacterium" a billion or
>>>> more years later than the first photosynthetic autotroph on a
direct line to the "first known." This
>>>> autotroph might well qualify as a "cyanobacterium" if we knew it
as intimately as we know extant ones.
>>>>
>>>> There is plenty of evidence, in the form of stromatolites and
banded iron formations, of the action of
>>>> photosynthetic autotrophs, going to maybe as billion years before
the Great Oxidation Event (GOE).
>>>> This article places the beginning of the GOE at 2.4 Ga, which
itself is half a billion years before
>>>> the "unambiguous" 1.9 Ga. for "the first known..."
>>>>
>>>> The 2.4 Ga dating seems to be "settled science":
>>>>
>>>> https://en.wikipedia.org/wiki/Great_Oxidation_Event
>> Here's where your new text begins, Erik:
>>> There are stromatolites ~3.5 Gy old, but the micro-organisms that
made them (assuming they aren't abiotic)
>>> are hard to identify.
>> Don't forget the independent evidence provided by banded iron
formations. More about them below.
>>> Most stromatolites don't contain identifiable bacteria,
>> I wrote up there about "identification bias". There is a practical
angle to it: one does not get
>> a paper accepted in prestigious journals by just writing
>>
>> "______ different kinds of bacterial cells were tallied on fossil
Stromatolite n.
>> Figures A through K show microphotographs of one representative of
each kind."
>>
>> One has to make a case for one or more prokaryotes being closely
related to __________
>> if one wants professionals to perk up.
>>> and there's no reason to
>>> believe modern examples contain the same micro-ecologies as the
fossils.
>> What sorts of micro-ecologies do you have in mind? One big
difference was the nonexistence of
>> macro-organisms like *Kimberella* of the Ediacaran period that fed
on bacterial mats.
>> We have plenty of animals today that fill a similar role, hence one
only finds stromatolites
>> under harsh conditions such as the high salinity (and, I've been
told, low oxygen) in Shark Bay, Australia.
>>
>> So, the environment back before 1 Ga was probably much more benign,
and so there might
>> be differences in the micro-ecology, but I have little idea of what
they might have been.
>>> Unambiguity is probably
>>> inevitable dealing with baterial remains as old as 1 Gy, even if
chemical signatures can be found. This
>>> summer I'm taking a trip to Wyoming to look at 2 Gy stromatolites
near Medicine Bow moutain.
>> Happy fossil hunting! Will you be joining a group?
>>> They're in conjuction/contact with microbial mat fossils, but
identification of specific organisms hasn't been made, that I'm aware of.
>> I first read about banded iron formations in an article by Isaak
Asimov, who was a chemist by profession.
>> He wrote that the early ocean had an enormous amount of ferrous
oxide dissolved in it.
>> [Unlike ferric oxide, which has one more oxygen atom, the ferrous is
appreciably soluble in water.]
>>
>> As oxygen came to be a waste product of various microorganisms [with
cyanobacteria believed to
>> be the big contributors early on], in the oceans, it would change
the ferrous form to the ferric, which
>> would precipitate out of the water and settle to the bottom,
building the next band in the formation.
>>
>> It wasn't until almost all the ferrous had been converted to ferric
that free oxygen had a chance to
>> build up, first in the water and then in the atmosphere, leading to
the GOE. After that, eukaryotes were able to come
>> out of obscurity by enveloping bacteria that were destined to become
mitochondria.
>>
>> For the sake of completeness, I should add that other things in the
environment were attacked
>> by the oxygen (which, next to fluorine and perhaps chlorine, is the
most reactive of the negatively acting elements)
>> and these, too, retarded the advent of the GOE.
>>
>>
>> Peter Nyikos
>> Professor, Department of Mathematics
>> University of So. Carolina at Columbia
>> http://people.math.sc.edu/nyikos
>
> No one seriously doubts that phototrophic bacteria existed before 1.8
Gya, but hard identification is problematic. The banded iron
> formations attest to their existence, as you say.
>
> Microbial mats and stromatolites now (and almost certainly then)
contain multiple organisms, and some sort of cyanobacteria
> was probably present in all the biotic examples. The pre-Ediacaran
environment lacked macro predators or grazers to best of our
> knowledge, but bacteria don't constitute the "peaceable kingdom".
The GOE made us possible, but at the time it would have
> been a catastrophe far exceeding AGW in its effects.
>
> My planned trip to Wyoming isn't with any group other than possibly a
few of my outback friends. The hunting will be very easy,
> as I have GPS coordinate points to many of the fossils of interest.
They're also very macroscopic, some measuring many
> meters in diameter.

Well, you know, one notable thing about all of this are the limiting
factors for life in the oceans now. To a great extent, one major one
is the fact that mineral ions can not get up to the photic zone of tens
of meters from the ocean's surface when the silt at the bottom of the
ocean might be more than a kilometer beneath that. On land of course
there is a vast array of metals in solid form very near where sunlight
is available if roots can get them and vascular systems can convey them
to leaves.

There is the possibility that the oceans may have had more life in them,
and not less, before oxygen, and the solubility of metal ions in water
could have been a major contributor to that if so.

Of course this is speculation. It is not quite obvious either way.