Origin and evolution of photosynthesis

Abstract

The atmosphere has apparently been oxygenated since the ‘Great Oxidation Event’ ca 2.4 Ga ago, but when the photosynthetic oxygen production began is debatable. However, geological and geochemical evidence from older sedimentary rocks indicates that oxygenic photosynthesis evolved well before this oxygenation event. Fluid-inclusion oils in ca 2.45 Ga sandstones contain hydrocarbon biomarkers evidently sourced from similarly ancient kerogen, preserved without subsequent contamination, and derived from organisms producing and requiring molecular oxygen. Mo and Re abundances and sulphur isotope systematics of slightly older (2.5 Ga) kerogenous shales record a transient pulse of atmospheric oxygen. As early as ca 2.7 Ga, stromatolites and biomarkers from evaporative lake sediments deficient in exogenous reducing power strongly imply that oxygen-producing cyanobacteria had already evolved. Even at ca 3.2 Ga, thick and widespread kerogenous shales are consistent with aerobic photoautrophic marine plankton, and U–Pb data from ca 3.8 Ga metasediments suggest that this metabolism could have arisen by the start of the geological record. Hence, the hypothesis that oxygenic photosynthesis evolved well before the atmosphere became permanently oxygenated seems well supported.

PHOTOSYNTHESIS AND THE ORIGIN OF LIFE

HYMAN HARTMAN
IASB, 880 Spruce St., Berkeley, CA 94707, U.S.A.
(Received 30 August, 1996)
Abstract.
The origin and evolution of photosynthesis is considered to be the key to the origin of life. This eliminates the need for a soup as the synthesis of the bioorganics are to come from the fixation of carbon dioxide and nitrogen. No soup then no RNAworld or Protein world. Cyanobacteria have been formed by the horizontal transfer of green sulfur bacterial photoreaction center genesby means of a plasmid into a purple photosynthetic bacterium. The fixation of carbon dioxide isconsidered to have evolved from a reductive dicarboxylic acid cycle (Chloroflexus) which was thenfollowed by a reductive tricarboxylic acid cycle (Chlorobium) and finally by the reductive pentosephosphate cycle (Calvin cycle). The origin of life is considered to have occurred in a hot springon the outgassing early earth. The first organisms were self-replicating iron-rich clays which fixedcarbon dioxide into oxalic and other dicarboxylic acids. This system of replicating clays and theirmetabolic phenotype then evolved into the sulfide rich region of the hotspring acquiring the ability to fix nitrogen. Finally phosphate was incorporated into the evolving system which allowed the synthesis of nucleotides and phospholipids. If biosynthesis recapitulates biopoesis, then the synthesis of aminoacids preceded the synthesis of the purine and pyrimidine bases. Furthermore the polymerization of the amino acid thioesters into polypeptides preceded the directed polymerization of amino acidesters by polynucleotides. Thus the origin and evolution of the genetic code is a late development and records the takeover of the clay by RNA.

Introduction

The major premise which underlies the field of either the ‘RNA world’ or the ‘Proteinoid world’ is the prior existence of a soup of monomers consisting of sugars, pyrimidine and purine bases and amino acids. In the old conundrum asto which came first the chicken (protein) or the egg (RNA), the answer is the chicken soup (of monomers). The major premise of this paper is that the soup is a hypothetical construct.  

In the absence of a soup the carbon entering the biosphere is in the form of carbon dioxide, the nitrogen is in the form of nitrogen gas, the hydrogen andoxygen enter the biosphere in the form of liquid water, the sulfur in the form of sulfide ion and the phosphate in the form of the phosphate ion.

The early atmosphere of the earth is considered to have been neutral (nitrogen and carbon dioxide). The problem arises of how oxygenic photosynthesis could have evolved under these conditions.There were abundant reducing agents such asferrous ion which made it unlikely that water would be used as an electron donor.It was thus suggested ‘that atmospheric hydrogen peroxide played a key role in inducing oxygenic photosynthesis because asperoxide increased in a localenvironment, organisms would not only be faced with a loss of reductant, but they would also be pressed to develop the biochemical apparatus (e.g., catalase) that would be ultimately be needed to protect against the products of oxygenic photosynthesis. This scenario allows for the early evolution of oxygen photosynthesis while global conditions were still anaerobic’ (McKay and Hartman, 1991).

Oxygenic photosynthesis developed in the cyanobacteria.The earliest bacterial fossils are found in the 3.5billion year old stromatolites of Western Australia. These fossil bacteria resemble cyanobacteria (Awramik, 1992).One possible conclusion from the ancient stromatolites and the bacterial fossils is that oxygenic photosynthesis was being carried out by the cyanobacteria 3.5billionyears ago.The cyanobacteria have two reaction centers; photosystem I and photosystem II. This is in contrast with the purple and the green photosynthetic bacteria which have only one reaction center. The purple bacteria have a pheophytin-quinone reaction center which is related to photosystem II. The green sulfur bacteria havea Fe-S reaction center which is related to photosystem I. ‘The simplest scenario giving rise to the linked photosystems found in oxygen-evolving organisms is that some sort of genetic fusion event took place between two bacteria, one with apheophytin-quinone reaction center and the other with an Fe-S reaction center.This produced a chimeric organism with two unlinked photosystems. Subsequently, the two photosystems were linked, and the oxygen evolving system added ’(Blankenship, 1992).

Price et al. look at plastids that were supposedly derived from cyanobacteria. These plastids all contain certain features that are similar to cyanobacteria, and those organisms that contain them are therefore thought to be along the same phylogenetic lineage. They include Glaucophyta, Rhodophyta, and green algae, along with their plant descendants.

 These three lineages are postulated to form the monophyletic group Plantae (or Archaeplastida), a hypothesis that suggests the primary cyanobacterial endosymbiosis occurred exclusively in their single common ancestor.

Unfortunately, as the authors point out, phylogenies based on other features, such as genetics, do not support the cyanobacteria- and plastid-derived phylogeny.

The idea of an endosymbiotic origin of plastids has become incontrovertible, but many important aspects of plastid origins remain obscured in the mists of more than a billion years of evolutionary history

Endosymbiosis is now a well substantiated theory that explains how cells gained their great complexity and was made famous most recently by the work of the late biologist Lynn Margulis, best known for her theory on the origin of eukaryotic organelles.

In a paper "Cyanophora paradoxa genome elucidates origin of photosynthesis in algae and plants" that appeared this week in the journal Science, an international team led by evolutionary biologist and Rutgers University professor Debashish Bhattacharya has shed light on the early events leading to photosynthesis, the result of the sequencing of 70 million base pair nuclear genome of the one-celled alga Cyanophora.

There are two schools of thought concerning the origin of reaction
centers and photosynthesis. One school pictures the evolution of
reaction centers beginning in the prebiotic phase
while the other school sees reaction centers evolving later from cytochrome b
in bacteria. Two models have been put forth for the subsequent evolution
of reaction centers in proteobacteria, green filamentous (non-sulfur) bacteria,
cyanobacteria, heliobacteria and green sulfur bacteria. In the selective loss model the most recent common ancestor
of all subsequent photosynthetic systems is postulated to have contained both RC1 and RC2. The evolution of
reaction centers in proteobacteria and green filamentous bacteria resulted from the loss of RC1, while the evolution
of reaction centers in heliobacteria and green sulfur bacteria resulted from the loss of RC2. Both RC1 and RC2
were retained in the cyanobacteria. In the fusion model the most recent common ancestor is postulated to have
given rise to two lines, one containing RC1 and the other containing RC2. The RC1 line gave rise to the reaction
centers of heliobacteria and green sulfur bacteria, and the RC2 line led to the reaction centers of proteobacteria
and green filamentous bacteria. The two reaction centers of cyanobacteria were the result of a genetic fusion of
an organism containing RC1 and an organism containing RC2. The evolutionary histories of the various classes
of antenna/light-harvesting complexes appear to be completely independent. The transition from anoxygenic to
oxygenic photosynthesis took place when the cyanobacteria learned how to use water as an electron donor for
carbon dioxide reduction. Before that time hydrogen peroxide may have served as a transitional donor, and before
that, ferrous iron may have been the original source of reducing power.


This hypothesis answers the problem of how
biosynthetic pathways to complex products could have
evolved by random mutation. The pathway is built
forward with each step fulfilling a useful function,
eventually to be replaced by the next step selected for
improved utility. Olson and Pierson (1987a, b) used the Granick
hypothesis to construct a hypothetical evolutionary
history of RCs from the biosynthetic pathways of Chl
a and BChla . They proposed that protochlorophyll
a might have functioned in a primitive RC at some time
before Chla existed, and that protoporphyrin IX and
Mg protoporphyrin IX might have served as RC pig-
ments before protochlorophyll a existed. In agreement
with Mauzerall (1978), Olson (1970, 1981) had previ-
ously interpreted the biosynthetic pathway of BChl
a to indicate that Chla had appeared before BChl a
in evolutionary history.

The nature of the ancient reductase that predated the
gene duplication is not known, but typically ancient
enzymes are both less specific and less efficient than
modern enzymes (Benner 2002).

Reaction centers

The evolution of photosynthesis begins with the evo-
lution of photochemical reaction centers (RCs). Two
schools of thought exist concerning the origin of
RCs and photosynthesis. The first school pictures the
evolution of RCs/photosynthesis beginning in the pre-
biotic phase (e.g., Mauzerall 1992; Hartman 1998)
whereas the second school sees RCs and photosyn-
thesis evolving much later from anaerobic respiration
in Bacteria (eubacteria) containing DNA, electron-
transport proteins, and ATP synthase (e.g., Meyer et al.
1996; Nitschke et al. 1998). The first school envi-
sions the evolution of photosynthesis and the origin
of life to be tightly intertwined; the second school
sees the origin of photosynthesis coming much later
than the appearance of the common ancestor of all
life. According to this view photosynthesis arose in
the Bacteria after they had separated from the Archaea
(archaebacteria).

378
Figure 2.
Hypothetical history of reaction center evolution based on protein homology.
See text for details. (Reprinted with permission of Data
Trace Publishing Company. Chemtracts Biochem Mol Biol 12: 468–482, 1999.)

all disagree with Olson and Pierson (1987a,
b) in one fundamental aspect. They propose that RC1
and RC2 evolved independently in different organ-
isms, and then were brought together in one organism
by genetic fusion to produce the cyanobacterial line
of photosynthesis with two photosystems in series.
Mathis (1990) proposed an evolutionary tree in which
genes for RC1 were transferred from a ‘heliobac-
terium’ to the genome of a ‘purple bacterium’ already
possessing genes for RC2. The resulting fusion be-
came the forerunner of the cyanobacteria. Blankenship
(1992) proposed that the ancestral RC evolved in two
directions simultaneously as shown in Figure 4. One
direction led to the evolution of RC2, and the other
direction led to RC1.


Antennas
LH1 and LH2 antenna complexes

Since both peptides are similar to helix D of subunit L
(bacterial RC2), the presumed ancient single helix or
homodimeric antenna complex may have been derived
from helix D of an ancient subunit L (Mulkidjian and
Junge 1997).

Phycobilisomes

Cyanobacteria and red algae contain supramolecu-
lar light-harvesting complexes called phycobilisomes,
that are attached to the stromal side of the photo-
synthetic membrane (Blankenship 2002). These com-
plexes can transfer excitation energy to the core
complex (CP43, CP47 and RC2) with more than
95% efficiency. The phycobilisomes consist of related
pairs of α and β phycobiliproteins (allophycocyanin,
phycocyanin and sometimes phycoerythrocyanin and
phycoerythrin). The phycobiliproteins are pigment
proteins that have evolved by multiple gene duplica-
tions and divergences from an ancestral form that
could form short rods (Grossman et al. 1995).

The most widespread source of reducing power in
late Archean and early Proterozoic (2.9–1.6 Ga) sea-
water was ferrous iron (0.1–1.0 mM) (Walker 1983),
and several authors (Olson 1978; Cohen 1984; Olson
and Pierson 1987a; Pierson and Olson 1989) proposed
that ferrous iron may have been an early electron
donor to PS II. The common ancestor of proteobacteria
and cyanobacteria might well have used Fe(OH)
+ as the principal electron donor for CO 2
fixation (Widdle et al. 1993; Ehrenreich and Widdle 1994; Heising
and Schink 1998). Because contemporary green sul-
fur bacteria utilize Fe(OH) +
rather poorly (Heising et al. 1999), one of us (Olson 2001) proposed that
the driving force for the evolution of RC2 in addi-
tion to RC1 was the necessity to utilize Fe(OH)
+ effectively for CO 2 fixation in the absence of reduced
sulfur compounds. However, some contemporary pro-
teobacteria can utilize Fe(OH) + for CO 2 fixation with
RC2 alone (Widdle et al. 1993; Ehrenreich and Widdle
1994).

Concluding remarks

This paper traces the history of thinking on how
photosynthesis originated and developed, from primit-
ive cells through anoxygenic photosynthetic bacteria,
through cyanobacteria and eventually to chloroplasts.
It is now clear that earlier attempts to reconstruct ‘the
path’ of evolutionary development were doomed to
failure. There have been many such paths that different
parts of the photosynthetic apparatus have followed,
which have not been the same in either of two classes
of organisms or even in different parts of the same
organism. Thus there is not one linear path that was
followed. The much more complex and non-linear
history that has taken place is challenging and inter-
esting to unravel, and will undoubtedly keep scientists
occupied for at least another 30 years

BILLIONS of years ago, a tiny cyanobacterium cracked open a water molecule - and let loose a poison that wrought death and destruction on an epic scale. The microbe had just perfected photosynthesis, ( amazing, how did it figure out that little trick ? ) a process that freed the oxygen trapped inside water and killed early Earth's anaerobic inhabitants.

Now, for the first time, geologists have found evidence of the crucial evolutionary stage just before cyanobacteria split water. The find offers a unique snapshot of the moment that made the modern world. With the advent of photosynthesis came an atmosphere dominated by oxygen and, ultimately, the diversity of life forms that we know today.

"This was the biggest change that ever occurred in the biosphere," says Kevin Redding at Arizona State University in Tempe. "The extinction caused by oxygen was probably the largest ever seen, but at the same time animal life wouldn't be possible without oxygen."

Photosynthesis uses light and a source of electrons to generate energy and power an organism. In the world as we know it, that source of electrons is water, with oxygen the waste product. But there are no signs that oxygen was being formed when photosynthesis first appeared around 3.4 billion years ago, so early photosynthesisers ( how did they come to be ? thats finally what we would like to know )  probably ( oh, so they don't know for sure ) scavenged electrons by splitting other molecules like hydrogen sulphide instead.

That had changed by about 2.4 billion years ago, when deposits of oxidised minerals tell us that oxygen was beginning to accumulate in the atmosphere. Photosynthesis as we know it had evolved.
( how do we know it evolved ?? )
To help work out how this happened, Woodward Fischer at the California Institute of Technology in Pasadena and his colleagues studied South African rocks that formed just before the 2.4-billion-year mark. Their analysis shows that although the rocks formed in the anoxic conditions that had prevailed since Earth's formation, all of the manganese in the rock was deposited in an oxidised form.

In the absence of atmospheric oxygen, manganese needs some sort of catalyst to help it oxidise - it won't react without a bit of help. The best explanation, say Fischer's team, is that a photosynthetic organism was using manganese as an electron source. That left unstable manganese ions behind, which reacted with water to form the oxides. Fischer presented the findings at the American Geophysical Union's conference in San Francisco on 6 December.

Every researcher contacted by New Scientist has hailed the significance of the study, in part because the evidence exactly matches what evolutionary theories have predicted.

A close look at today's plants and algae shows that manganese oxidation is still a vital part of photosynthesis. Within their photosynthetic structures are manganese-rich crystals that provide the electrons to drive photosynthesis. The crystals then snaffle electrons from passing water molecules to restore their deficit. It is this electron raid that cracks open water molecules and generates the oxygen we breathe.

This complicated process must have had simpler roots. In 2007, John Allen at Queen Mary, University of London, and William Martin at the University of Düsseldorf, Germany, suggested one scenario (Nature, doi.org/bs65kb).

They believe that modern photosynthesis was born when early cyanobacteria by chance floated into a watery environment rich in manganese, and quickly adapted to take advantage of the new source of electrons.

They adapted ?? How did that happen ?

Later, because manganese is a relatively scarce resource that can't be tapped indefinitely, the cyanobacteria evolved a different strategy. They incorporated manganese directly into their photosynthetic structures ( i have still not seen a explanation of how photosynthesis evolved in them )


and used it as a rechargeable battery: draining it of its electrons, but allowing its supplies to be replenished by stealing electrons from another, more plentiful source - water.

What Fischer's team has found is evidence of the initial step in this process: an anoxic environment rich in manganese that has been stripped of electrons and left in an oxidised state, almost certainly by primitive cyanobacteria. "There had to be some intermediate step in the evolutionary process," says Redding.

"This is big news," says Martin. He adds that we can expect publications in the near future that provide more evidence compatible with the theory. "But this somewhat more direct geochemical evidence is really exciting."

SO , THAT ARE ALL UNSUPPORTED CLAIMS, AD HOC EXPLANATIONS WITHOUT EXPERIMENTAL EVIDENCE WHATSOEVER, AND NEIThER DETAILED EXPLANATIONS HOW THE EVOLUTIONARY PROCESS OF PHOTOSYNTHESIS HAPPENED....

Chlorophyll itself, and many of the intermediates along its pathway of synthesis can form triplet states, which would destroy surrounding lipids by a free radical cascade apart from the context of the enzymes that manufacture them and the apoproteins into which they are inserted at the conclusion of their synthesis.
‘triplet excited pigments are physiologically equivalent to the active oxygens’, and according to Sandmann and Scheer, chlorophyll triplets ‘are already highly toxic by themselves … .’

The entire process of chlorophyll synthesis from δ-aminolevulinic acid to protoporphyrin IX is apparently tightly coupled to avoid leakage of intermediates. Almost all of the enzymes of chlorophyll biosynthesis are involved in handling phototoxic material. For many of these enzymes, if they are not there when their substrate is manufactured, the cell will be destroyed by their substrate on the loose in the wrong place at the wrong time.

For four of the enzymes of chlorophyll biosynthesis for which this has been proven to be the case. This is a significant problem for evolutionists, who need time for these enzymes to evolve successively. Each time a new enzyme evolved it would have produced a new phototoxin until the next enzyme evolved.

Triplet state chlorophyll, generated in the reaction centres when singlet (excited state) chlorophyll cannot get rid of its energy quickly enough, as may be the case when excess photon energy is coming in, lasts long enough to generate very damaging singlet oxygen , which attacks lipids, proteins, chlorophyll and DNA. Evolutionists maintain that ground-state oxygen (3O2, a triplet state biradical) was not around when photosynthesis evolved.

There is, however, considerable evidence that there has never been a time in Earth’s history when there was not significant free oxygen in the atmosphere (see Dimroth and Kimberley,32 Thaxton, Bradley and Olsen,33 Overman and Pannenberg,34 Denton35).

The evolutionists’ own analyses suggest that the last common ancestor for the bacteria and archaea already had sophisticated enzyme systems for using O2 and for disarming its reactive by-products.36 Since these organisms had already evolved by 3.5 Ga, on the evolutionists’ timescale, this also suggests something rather ominous for the absence of oxygen theory.

In the system that presently exists, a sophisticated complex of enzymes and pigments quenches the excess energy and scavenges the dangerous oxygen species generated by excess light. CuZn superoxide dismutase (in most higher plants) converts superoxide (O2-), the primary product of photoreduction of dioxygen in PSI,38 to H2O2 in the highest-known diffusion-controlled rate among enzymatic reactions. It appears that about one molecule of superoxide dismutase attaches to the surface of the membrane in the vicinity of the PSI complex, along with ascorbate peroxidase (APX). Ascorbate reduces the H2O2 generated, in a reaction catalyzed by APX. The product of this reaction, the monodehydroascorbate radical, is reduced again to ascorbate by photoreduced ferredoxin (Fd) in PSI.

The enzymes and other reducing species of this system could not evolve gradually and then microcompartmentalize over time because nothing works unless everything is in place.

This means that the first appearance of oxygen would have been lethal to the cell, whether the source of oxygen was biological or non-biological. Enzymes such as superoxide dismutase would not have been able to evolve at all. APX, for example, has only about 31–33% homology with cytochrome c peroxidase, from which it is thought to have evolved. Cells without these enzymes exposed to ground-state oxygen would simply have been destroyed before hundreds of base pair changes generated the enzymes from something else.


Natural selection is not evolution’s friend. In answer to the question, ‘Why would evolution produce a series of enzymes that only generate useless intermediates until all of the enzymes needed for the end product have evolved?’

The question, ‘Why and how would evolution go about trying to produce a protein for binding pigment molecules before pigment molecules existed?’ is another major challenge for evolutionists.

If chlorophyll evolved before the antenna proteins that bind it, it would in all likelihood destroy the cell, so the proteins had to evolve first. But natural selection could not favour a ‘newly evolved’ protein which could bind chlorophyll and other pigment molecules before those crucial pigments had themselves come into existence!

Each binding site must be engineered to bind chlorophyll a or chlorophyll b only or carotene only. The carotene molecules must be present in just the right places for quenching triplet states in the chlorophylls.

Even if the pigment molecules were already around, producing just the right protein would be an extremely difficult task. It would not only have to bind pigment molecules only, but it would need to bind just the right pigments in just the right places in just the right orientation so that energy could be transferred perfectly between them, with a little lower energy at each step. Anything else would do nothing, or would transfer energy at random, and the complex would accomplish nothing at best and burn up the cell at worst.


And there is another problem for evolution. The insertion of the pigment molecules changes the conformation of the apoprotein from about 20% to about 60% α-helical content.45 So evolution would have to produce a protein with a wrong shape that would assume just the right shape by the insertion of pigment molecules in just the right positions and orientations when those pigment molecules had not yet evolved.

The energy transfer timeframe between pigment molecules in the antenna complex is between 10-15 and 10-9 seconds. The system that God engineered captures 95–99% of the photon energy for photochemistry, even though there are four other ways the energy can be lost during the slightly less than a billionth of a second the system has for capturing it.46 Humans certainly cannot begin to design systems with such efficiency, but the evolutionists are determined that chance, what Cairns-Smith47 calls ‘old fumble fingers’, can.

Our understanding of the assembly of apoproteins with their pigments is very poor, but we do know that the chloroplast encoded chlorophyll a binding proteins of PSI and PSII core complexes are inserted cotranslationally into the thylakoid.

Protein intermediates of the D1 protein have been observed due to ribosome pausing. It may be that this ribosome pausing permits cotranslational binding of chlorophyll a to the protein. This kind of controlled insertion, with synthesis of otherwise phototoxic material, is precisely what we would expect from intelligent planning and forethought, but how might ‘old fumble fingers’ hit on such a scheme?

Evolutionary Relationships Among Photosynthetic Bacteria

Origin of Photosynthesis

this key fundamental innovation which either directly or indirectly sustains all eukaryotic organisms, originated within the prokaryotes.

Within prokaryotes, photosynthetic capability is present within five major groups of bacteria:

Firmicutes or the low G+C Gram-positive bacteria (Heliobacterium),
Chloroflexi or Green nonsulfur bacteria,
Chlorobi or Greensulfur bacteria,
Proteobacteria and,
Cyanobacteria.


Of these only Cyanobacteria, which contains two different reaction centers (RC) RC-1 and RC-2 (or PS I and PS II) linked to each other, are capable of carrying out oxygenic photosynthesis. All other photosynthetic bacteria carry out only anoxygenic photosynthesis and contain a single reaction center. Of these Heliobacteria and Chlorobi contain Fe-S type of reaction centers (RC-1) whereas Chloroflexi and Proteobacteria have a pheophytin-quinone type of reaction center (RC-2). The similarities of these RCs in component parts and the mechanisms of charge transfer indicate that they have evolved from a common ancestor. To understand the origin of photosynthesis and which of these reaction centers first evolved, it is essential to understand the branching order of different photosynthetic phyla from a common ancestor, which is not resolved by traditional phylogenetic means. However, based upon the signature sequence approach the branching orders of different bacteria phyla can now be reliably deducted (see diagram on above)

1. Earliest Branching Photosynthetic Bacteria

Firmicutes (Heliobacterium) are indicated to be earliest branching photosynthetic bacteria. The ancestral nature of this group is also supported by a number of other observations:

Unlike other photosynthetic bacteria, both antenna and reaction center activities are present within a single protein in Heliobacteria;
The reaction center complex in Heliobacteria (and also green sulfur bacteria) has a simpler homodimeric structure as opposed to being heterodimeric in other photosynthetic bacteria;
The RC in Heliobacteria contains a unique photosynthetic pigment Bchl g, which is indicated to be primitive in comparison to the pigments found in other photosynthetic organisms.
Of the different photosynthetic bacteria, only Heliobacteria are bounded by a single unit lipid membrane (monoderm cell structure), which is indicated to be an ancestral characteristic in comparison to the cells containing both an inner and outer cell membranes (Diderm cell structure).

2. The Second Photosynthetic Bacteria

Following Heliobacteria, Chloroflexi are indicated to be the next group of photosynthetic organisms that branched off from the common ancestor. The branching of both Heliobacteria and Chloroflexi prior to Cyanobacteria provides evidence that both RC-1 and RC-2 had already evolved prior to the emergence of Cyanobacteria, which contain both of these reactions centers linked to each other.

3. Anoxygenic Photosynthesis vs Oxygenic Photosynthesis

The bacterial groups utilizing anoxygenic photosynthesis mode evolved much earlier than those capable of oxygenic photosynthesis. This is in accordance with the observation that change in atmosphere from anoxygenic to oxygenic occurred much later (between 1.5-2 billion year) after the evolution of earlier organisms. This observation indicates that the earlier prokaryotic fossils probably do not correspond to Cyanobacteria but some other groups of photosynthetic bacteria.

4. Later Branching Photosynthetic Bacteria

The later branching photosynthetic phyla which contain either one or both of these RCs could have acquired such genes from the earlier branching lineages by either direct descent or by means of lateral gene transfer.

5. Speculations About the Earliest Organism

The presence of photosynthetic ability in the earliest branching bacterial phylum indicates that photosynthesis evolved very early in evolution and it is possible that the earliest organism that evolved were photosynthetic.

Another problem facing evolutionist scientists who expect bacteria to produce their own food is the difficulty of the endeavour. In the preceding sections we stressed that photosynthesis depends upon very complex systems. And of all the processes known in the world, this is really the most complicated, its general outlines having been only partly uncovered in our day; many of its stages are still a mystery to man.

Prof. Dr. Ali Demirsoy, Kalitim ve Evrim (Inheritance and Evolution), Ankara, Metek

This is what evolutionist scientists expect of a dying bacteria: that it should by itself develop this process - a process which has not been artificially reproduced even in reactors with the most highly developed technology. One of the most striking admissions that such a complicated event as photosynthesis could not have evolved over time is again made by
Photosynthesis is a rather complicated event, and it seems impossible for it to emerge in an organelle inside a cell, because it is impossible for all the stages to have come about at once, and it is meaningless for them to have emerged separately.