Membrane Biochemistry Challenges Route to Evolutionary Origin of Complex Cells

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By Fazale Rana – July 10, 2019

Unfortunately, the same thing could be said to biologists trying to discover the evolutionary route that led to the emergence of complex, eukaryotic cells. No matter the starting point, it seems as if you just can’t get there from here.

This frustration becomes most evident as evolutionary biologists try to account for the biochemical makeup of the membranes found in eukaryotic cells. In my opinion, this struggle is not just an inconvenient detour. As the following paragraphs show, obstacles line the roadway, ultimately leading to a dead end that exposes the shortcomings of the endosymbiont hypothesis—a cornerstone idea in evolutionary biology.

Endosymbiont Hypothesis

Most biologists believe that the endosymbiont hypothesis stands as the best explanation for the origin of complex cells. According to this hypothesis, complex cells originated when symbiotic relationships formed among single-celled microbes after free-living bacterial and/or archaeal cells were engulfed by a “host” microbe.

The mitochondrion represents the “poster child” of the endosymbiont hypothesis. Presumably, this organelle started as an endosymbiont. Evolutionary biologists believe that once engulfed by the host cell, the microbe took up permanent residency, growing and dividing inside the host. Over time, the endosymbiont and host became mutually interdependent, with the endosymbiont providing a metabolic benefit—such as a source of ATP—for the host cell. In turn, the host cell provided nutrients to the endosymbiont. Presumably, the endosymbiont gradually evolved into an organelle through a process referred to as genome reduction. This reduction resulted when genes from the endosymbiont’s genome were transferred into the genome of the host organism.

Evidence for the Endosymbiont Hypothesis
1. Most of the evidence for the endosymbiont hypothesis centers around mitochondria and their similarity to bacteria. Mitochondria are about the same size and shape as a typical bacterium and have a double membrane structure like gram-negative cells. These organelles also divide in a way that is reminiscent of bacterial cells.

2. Biochemical evidence also exists for the endosymbiont hypothesis. Evolutionary biologists view the presence of the diminutive mitochondrial genome as a vestige of this organelle’s evolutionary history. They see the biochemical similarities between mitochondrial and bacterial genomes as further evidence for the evolutionary origin of these organelles.

3. The presence of the unique lipid, cardiolipin, in the mitochondrial inner membrane also serves as evidence for the endosymbiont hypothesis. This important lipid component of bacterial inner membranes is not found in the membranes of eukaryotic cells—except for the inner membranes of mitochondria. In fact, biochemists consider it a signature lipid for mitochondria and a vestige of the organelle’s evolutionary history. So far, the evolutionary route looks well-paved and clear.

Discovery of Lokiarchaeota

Evolutionary biologists have also developed other lines of evidence in support of the endosymbiont hypothesis. For example, biochemists have discovered that the genetic core (DNA replication and the transcription and translation of genetic information) of eukaryotic cells resembles that of the archaea. This similarity suggests to many biologists that a microbe belonging to the archaeal domain served as the host cell that gave rise to eukaryotic cells.

Life scientists think they may have determined the identity of that archaeal host. In 2015, a large international team of collaborators reported the discovery of Lokiarchaeota, a new phylum belonging to the archaea. This phylum clusters with eukaryotes on the evolutionary tree. Analysis of the genomes of Lokiarchaeota identifies a number of genes involved in membrane-related activities, suggesting that this microbe may well have possessed the ability to engulf other microbes.1 At this point, it looks like “you can get there from here.”

Challenges to the Endosymbiont Hypothesis

Despite this seemingly compelling evidence, the evolutionary route to the first eukaryotic cells is littered with potholes. I have written several articles detailing some of the obstacles. (See Challenges to the Endosymbiont Hypothesis in the Resources section.) Also, a divide on the evolutionary roadway called the lipid divide compounds the problem for the endosymbiont hypothesis.

Lipid Divide

The lipid divide refers to the difference in the chemical composition of the cell membranes found in bacteria and archaea. Phospholipids comprise the cell membranes of both sorts of microbes. But the similarity ends there. The chemical makeup of the phospholipids is distinct in bacteria and archaea.

Bacterial phospholipids are built around a d-glycerol backbone, which has a phosphate moiety bound to the glycerol in the sn-3 position. Two fatty acids are bound to the d-glycerol backbone at the sn-1 and sn-2 positions. In water, these phospholipids assemble into bilayer structures.

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Figure: Difference between archaeal (top) and bacterial (middle and bottom) phospholipids. Features include 1: isoprene chains, 2: ether linkage, 3: l-glycerol, 4 and 8: phosphate group, 5: fatty acid chains, 6: ester linkages, 7: d-glycerol, 9: lipid bilayer of bacterial membranes, 10: lipid monolayer found in some archaea. Image credit: Wikipedia

Archaeal phospholipids are constructed around an l-glycerol backbone (which produces membrane lipids with different stereochemistry than bacterial phospholipids). The phosphate moiety is attached to the sn-1 position of glycerol. Two isoprene chains are bound to the sn-2 and sn-3 positions of l-glycerol via ether linkages. Some archaeal membranes are formed from phospholipid bilayers, while others are formed from phospholipid monolayers.

Presumably, the structural features of the archaeal phospholipids serve as an adaptation that renders them ideally suited to form stable membranes in the physically and chemically harsh environments in which many archaea find themselves.

Lipid Divide Frustrates the Origin of Eukaryotic Cell Membranes

In light of the lipid divide and the evidence that seemingly indicates that the endosymbiotic host cell likely belonged to Lokiarchaeota, it logically follows that the membrane composition of eukaryotic cells should be archaeal-like. But, this expectation is not met and the evolutionary route encounters another pothole. Instead, the cell membranes of eukaryotic cells closely resemble bacterial membranes.

One way to repair the roadway is to posit that during the evolutionary process that led to the emergence of eukaryotic cells, a transition from archaeal-like membranes to bacterial-like membranes took place. In fact, supporting evidence comes from laboratory studies demonstrating that stable bilayers can form from a mixture of bacterial and archaeal phospholipids, even though the lipids from the two sources have opposite stereochemistry.

Evolutionary biologists Purificación López-García and David Moreira question if evidence can be marshaled in support of this scenario for two reasons.2 First, mixing of phospholipids in the lab is a poor model for cell membranes that function as a “dynamic cell-environment interface.”3

Second, they question if this transition is feasible given how exquisitely optimized membrane proteins must be to fit into cell membranes. The nature of protein optimization is radically different for bacterial and archaeal membranes. Because cell membrane systems are optimized, the researchers question if an adequate driving force for this transition exists.

In other words, these two scientists express serious doubts about the biochemical viability of a transitional stage between archaeal membranes. In light of these obstacles, López-García and Moreira write, “The archaea-to-bacteria membrane shift remains the Achilles’ heel for these models [that propose an archaeal host for endosymbionts].”4

In other words, you can’t get there from here.

Can Lokiarchaeota Traverse the Lipid Divide?

In the midst of this uncertain evolutionary route, a recent study by investigators from the Netherlands seems to point the way toward the evolutionary origin of eukaryotic membranes.5 Researchers screened the Lokiarchaeota genome for enzymes that would take part in phospholipid synthesis with the hope of finding clues about how this transition may have occurred. They conclude that this group of microbes could not make l-glycerol-1-phosphate (a key metabolic intermediate in the production of archaeal phospholipids) because it lacked the enzyme glycerol-1-phosphate dehydrogenase (G1PDH). They also discovered evidence that suggests that this group of microbes could make fatty acids and chemically attach them to sugars. The researchers argue that Lokiarchaeota could make some type of hybrid phospholipid with features of both archaeal and bacterial phospholipids.

The team’s approach to understanding how evolutionary processes could bridge the lipid divide and account for the origin of eukaryotic membranes is clever and inventive, to be sure. But it is far from convincing for at least four reasons.

1. Absence of evidence is not evidence of absence, as the old saying goes. Just because the research team didn’t find the gene for G1PDH in the Lokiarchaeota genetic material doesn’t mean this microbe didn’t have the capacity to make archaeal-type phospholipids. Toward this end, it is important to note that researchers have not cultured any microbe that belongs to this group organisms. The group’s existence is inferred from metagenomic analysis, which involves isolating small fragments of DNA from the environment (in this case a hydrothermal vent system in the Atlantic Ocean, called Loki’s Castle) and stitching them together into a genome. The Lokiarchaeota “genome” is low quality (1.4-fold coverage) and incomplete (8 percent of the genome is missing). Around one-third (32 percent) of the genome codes for proteins with unknown function. Could it be that an enzyme capable of generating l-glycerol-1-phosphate exists in the mysterious third of the genome? Or in the missing 8 percent?

2. While the researchers discovered that genes could conceivably work together to make d-glycerol-3-phosphate (though the enzymes encoded by these genes perform different metabolic functions), they found no direct evidence that Lokiarchaeota produces d-glycerol-3-phosphate. Nor did they find evidence for glycerol-3-phosphate dehydrogenase (G3PDH) in the Lokiarchaeota genetic material. This enzyme plays a key role in the synthesis of phospholipids in bacteria.

3. Though the researchers found evidence that Lokiarchaeota had the capacity to make fatty acids, some of the genes required for the process seem to have been acquired by these microbes via horizontal gene transfer with genetic material from bacteria. (It should be noted that 29 percent of the Lokiarchaeota genome comes from the bacteria.) It is not clear when Lokiarchaeota acquired these genes and, therefore, if this metabolic capability has any bearing on the origin of eukaryotes.

4. The researchers present no evidence that Lokiarchaeota possessed the protein machinery that would chemically attach isoprenoid lipids to d-glycerol-3-phosphate via ether linkages.

Thus, the only way to establish Lokiarchaeota membranes as a transitional evolutionary pathway between those found in Archaea and Bacteria is to perform chemical analysis of its membranes. At this juncture, such analysis is impossible to perform because no one has been able to culture Lokiarchaeota. In fact, other evidence suggests that this group of microbes possessed archaeal-type membranes. Researchers have recovered archaeal lipids in the sediments surrounding Loki’s Castle, but they have not recovered bacterial-like lipids.

More Lipid Divide Frustration

Given these problems, could it be that the host microbe for the endosymbiont was a member of Bacteria, not Archaea? While this model would solve the problem of the lipid divide, it leaves unexplained the similarity between the genetic core of eukaryotes and the Archaea. Nor does it account for the grouping of eukaryotes with the Archaea.

It doesn’t look like you can get there from here, either.

Evolutionary biologists Jonathan Lombard, Purificación López-García and David Moreira sum things up when they write, “The origin of eukaryotic membranes is a problem that is rarely addressed by the different hypotheses that have been proposed to explain the emergence of eukaryotes.”6 Yet, until this problem is adequately addressed, the evolutionary route to eukaryotes will remain obscure and the endosymbiont hypothesis noncompelling.

In light of this challenge and others, maybe a better way to make sense of the origin of eukaryotic cells is to view them as the Creator’s handiwork. For many scientists, it is a road less traveled, but it accounts for all of the data. You can get there from here.

Resources

Challenges to the Endosymbiont Hypothesis

Support for a Creation Model for the Origin of Eukaryotic Cells

Endnotes
  1. Anja Spang et al., “Complex Archaea that Bridge the Gap between Prokaryotes and Eukaryotes,” Nature 521 (May 14, 2015): 173–79, doi:10.1038/nature14447; Katarzyna Zaremba-Niedzwiedzka et al., “Asgard Archaea Illuminate the Origin of Eukaryotic Cellular Complexity,” Nature 541 (January 19, 2017): 353–58, doi:10.1038/nature21031.
  2. Purificación López-García and David Moreira, “Open Questions on the Origin of Eukaryotes,” Trends in Ecology and Evolution 30, no. 11 (November 2015): 697–708, doi:10.1016/j.tree.2015.09.005.
  3. López-García and Moreira, “Open Questions.”
  4. López-García and Moreira, “Open Questions.”
  5. Laura Villanueva, Stefan Schouten, and Jaap S. Sinninghe Damsté, “Phylogenomic Analysis of Lipid Biosynthetic Genes of Archaea Shed Light on the ‘Lipid Divide,’” Environmental Microbiology 19, no. 1 (January 2017): 54–69, doi:10.1111/1462-2920.13361.
  6. Jonathan Lombard, Purificación López-García, and David Moreira, “The Early Evolution of Lipid Membranes and the Three Domains of Life,” Nature Reviews Microbiology 10 (June 11, 2012): 507–15, doi:10.1038/nrmicro2815.

Reprinted with permission by the author

Original article at:
https://reasons.org/explore/blogs/the-cells-design

The Endosymbiont Hypothesis: Things Aren’t What They Seem to Be

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BY FAZALE RANA – AUGUST 29, 2018

Sometimes, things just aren’t what they seem to be. For example, when it comes to the world of biology:

  • Fireflies are not flies; they are beetles
  • Prairie dogs are not dogs; they are rodents
  • Horned toads are not toads; they are lizards
  • Douglas firs are not firs; they are pines
  • Silkworms are not worms; they are caterpillars
  • Peanuts are not nuts; they are legumes
  • Koala bears are not bears; they are marsupials
  • Guinea pigs are not from Guinea and they are not pigs; they are rodents from South America
  • Banana trees are not trees; they are herbs
  • Cucumbers are not vegetables; they are fruit
  • Mexican jumping beans are not beans; they are seeds with a larva inside

And . . . mitochondria are not alphaproteobacteria. In fact, evolutionary biologists don’t know what they are—at least, if recent work by researchers from Uppsala University in Sweden is to be taken seriously.1

As silly as this list may be, evolutionary biologists are not amused by this latest insight about the identity of mitochondria. Uncertainty about the evolutionary origin of mitochondria removes from the table one of the most compelling pieces of evidence for the endosymbiont hypothesis.

A cornerstone idea within the modern evolutionary framework, biology textbooks often present the endosymbiont hypothesis as a well-evidenced, well-established evolutionary explanation for the origin of complex cells (eukaryotic cells). Yet, confusion and uncertainty surround this idea, as this latest discovery attests. To put it another way: when it comes to the evolutionary explanation for the origin of complex cells in biology textbooks, things aren’t what they seem.

The Endosymbiont Hypothesis

Most evolutionary biologists believe that the endosymbiont hypothesis is the best explanation for one of the key transitions in life’s history—namely, the origin of complex cells from bacteria and archaea. Building on the ideas of Russian botanist Konstantin Mereschkowski, Lynn Margulis (1938–2011) advanced the endosymbiont hypothesis to explain the origin of eukaryotic cells in the 1960s.

Since that time, Margulis’s ideas on the origin of complex cells have become an integral part of the evolutionary paradigm. Many life scientists find the evidence for this hypothesis compelling; consequently, they view it as providing broad support for an evolutionary explanation for the history and design of life.

According to this hypothesis, complex cells originated when symbiotic relationships formed among single-celled microbes after free-living bacterial and/or archaeal cells were engulfed by a “host” microbe. (Ingested cells that take up permanent residence within other cells are referred to as endosymbionts.)

the-endosymbiont-hypothesis

The Evolution of Eukaryotic Cells According to the Endosymbiont Hypothesis

Image source: Wikipedia

Presumably, organelles such as mitochondria were once endosymbionts. Evolutionary biologists believe that once taken inside the host cell, the endosymbionts took up permanent residence, with the endosymbiont growing and dividing inside the host. Over time, endosymbionts and hosts became mutually interdependent, with the endosymbionts providing a metabolic benefit for the host cell. The endosymbionts gradually evolved into organelles through a process referred to as genome reduction. This reduction resulted when genes from endosymbionts’ genomes were transferred into the genome of the host organism. Eventually, the host cell evolved machinery to produce proteins needed by the former endosymbiont and processes to transport those proteins into the organelle’s interior.

Evidence for the Endosymbiont Hypothesis

The morphological similarity between organelles and bacteria serve as one line of evidence for the endosymbiont hypothesis. For example, mitochondria are about the same size and shape as a typical bacterium and they have a double membrane structure like the gram-negative cells. These organelles also divide in a way that is reminiscent of bacterial cells.

Biochemical evidence also seems to support the endosymbiont hypothesis. Evolutionary biologists view the presence of the diminutive mitochondrial genome as a vestige of this organelle’s evolutionary history. Additionally, biologists also take the biochemical similarities between mitochondrial and bacterial genomes as further evidence for the evolutionary origin of these organelles.

The presence of the unique lipid cardiolipin in the mitochondrial inner membrane also serves as evidence for the endosymbiont hypothesis. Cardiolipin is an important lipid component of bacterial inner membranes. Yet, it is not found in the membranes of eukaryotic cells—except for the inner membranes of mitochondria. In fact, biochemists consider it a signature lipid for mitochondria and a vestige of this organelle’s evolutionary history.

But, as compelling as these observations may be, for many evolutionary biologists phylogenetic analysis provides the most convincing evidence for the endosymbiont hypothesis. Evolutionary trees built from the DNA sequences of mitochondria, bacteria, and archaea place these organelles among a group of microbes called alphaproteobacteria. And, for many (but not all) evolutionary trees, mitochondria cluster with the bacteria, Rickettsiales.For evolutionary biologists, these results mean that the endosymbionts that eventually became the first mitochondria were alphaproteobacteria. If mitochondria were notevolutionarily derived from alphaproteobacteria, why would the DNA sequences of these organelles group with these bacteria in evolutionary trees?

But . . . Mitochondria Are Not Alphaproteobacteria

Even though evolutionary biologists seem certain about the phylogenetic positioning of mitochondria among the alphaproteobacteria, there has been an ongoing dispute as to the precise positioning of mitochondria in evolutionary trees, specifically whether or not mitochondria group with Rickettsiales. Looking to bring an end to this dispute, the Uppsula University research team developed a more comprehensive data set to build their evolutionary trees, with the hope that they could more precisely locate mitochondria among alphaproteobacteria. The researchers point out that the alphaproteobacterial genomes used to construct evolutionary trees stem from microbes found in clinical and agricultural settings, which is a small sampling of the alphaproteobacteria found in nature. Researchers knew this was a limitation, but, up to this point, this was the only DNA sequence data available to them.

To avoid the bias that arises from this limited data set, the researchers screened databases of DNA sequences collected from the Pacific and Atlantic Oceans for undiscovered alphaproteobacteria. They uncovered twelve new groups of alphaproteobacteria. In turn, they included these new genome sequences along with DNA sequences from previously known alphaproteobacterial genomes to build a new set of evolutionary trees. To their surprise, their analysis indicates that mitochondria are not alphaproteobacteria.

Instead, it looks like mitochondria belong to a side branch that separated from the evolutionary tree before alphaproteobacteria emerged. Adding to their surprise, the research team was unable to identify any bacterial species alive today that would group with mitochondria.

To put it another way: the latest study indicates that evolutionary biologists have no candidate for the evolutionary ancestor of mitochondria.

Does the Endosymbiont Hypothesis Successfully Account for the Origin of Mitochondria?

Evolutionary biologists suggest that there’s compelling evidence for the endosymbiont hypothesis. But when researchers attempt to delineate the details of this presumed evolutionary transition, such as the identity of the original endosymbiont, it becomes readily apparent that biologists lack a genuine explanation for the origin of mitochondria and, in a broader context, the origin of eukaryotic cells.

As I have written previously, the problems with the endosymbiont hypothesis are not limited to the identity of the evolutionary ancestor of mitochondria. They are far more pervasive, confounding each evolutionary step that life scientists envision to be part of the emergence of complex cells. (For more examples, see the Resources section.)

When it comes to the endosymbiont hypothesis, things are not what they seem to be. If mitochondria are not alphaproteobacteria, and if evolutionary biologists have no candidate for their evolutionary ancestor, could it be possible that they are the handiwork of the Creator?

Resources

Endnotes

  1. Joran Martijn et al., “Deep Mitochondrial Origin Outside the Sampled Alphaproteobacteria,” Nature 557 (May 3, 2018): 101–5, doi:10.1038/s41586-018-0059-5.
Reprinted with permission by the author
Original article at:
https://www.reasons.org/explore/blogs/the-cells-design/read/the-cells-design/2018/08/29/the-endosymbiont-hypothesis-things-aren-t-what-they-seem-to-be

Can a Creation Model Explain the Origin of Mitochondria?

canacreationmodelexplaintheorigin

BY FAZALE RANA – NOVEMBER 23, 2016

Some called her a scientific heretic. Others were a bit more kind, describing her as a maverick.

Lynn Margulis (1938–2011) earned her reputation in the late 1960s when she proposed the endosymbiont hypothesis for the origin of eukaryotic cells. Because her ideas about evolution didn’t conform to Darwinian principles, evolutionary biologists summarily dismissed her idea out of hand and then went on to ignore her work for a couple of decades. She was ultimately vindicated, however, as the endosymbiont hypothesis gradually gained acceptance.

Today, Margulis’s proposal has become a cornerstone idea of the evolutionary paradigm and is taught in introductory high school and college biology courses. This classroom exposure explains why I am often asked about the endosymbiont hypothesis when I speak on university campuses. Many first-year biology students and professional life scientists alike find the evidence for this idea compelling, and consequently view it as providing broad support for an evolutionary explanation for the history and design of life.

Yet, new work by biochemists from Cambridge University make it possible to account for the origin of eukaryotic cells from a creation model perspective, providing a response to the endosymbiont hypothesis.1

The Endosymbiont Hypothesis

According to this hypothesis, complex cells originated when symbiotic relationships formed among single-celled microbes after free-living bacterial and/or archaeal cells were engulfed by a “host” microbe. (Ingested cells that take up permanent residence within other cells are referred to as endosymbionts.)

Accordingly, organelles, such as mitochondria, were once endosymbionts. Once taken inside the host cell, the endosymbionts presumably took up permanent residency within the host, with the endosymbionts growing and dividing inside the host. Over time, the endosymbionts and the host became mutually interdependent, with the endosymbionts providing a metabolic benefit for the host cell. The endosymbionts gradually evolved into organelles through a process referred to as genome reduction. This reduction resulted when genes from the endosymbionts’ genomes were transferred into the genome of the host organism. Eventually, the host cell evolved both the machinery to produce the proteins needed by the former endosymbiont and the processes needed to transport those proteins into the organelle’s interior.

Evidence for the Endosymbiont Hypothesis

The main line of evidence for the endosymbiont hypothesis is the similarity between organelles and bacteria. For example, mitochondria—which are believed to be descended from a group of α-proteobacteria—are about the same size and shape as a typical bacterium and have a double membrane structure like gram-negative cells. These organelles also divide in a way that is reminiscent of bacterial cells.

There is also biochemical evidence for the endosymbiont hypothesis. Evolutionary biologists view the existence of the diminutive mitochondrial genome as a vestige of this organelle’s evolutionary history. Additionally, the biochemical similarities between mitochondrial and bacterial genomes are taken as further evidence for the evolutionary origin of these organelles.

The presence of the unique lipid called cardiolipin in the mitochondrial inner membrane also serves as evidence for the endosymbiont hypothesis. Cardiolipin is an important lipid component of bacterial inner membranes, yet it is not found in the membranes of eukaryotic cells—except for the inner membranes of mitochondria. In fact, biochemists consider it a signature lipid for mitochondria and a vestige of this organelle’s evolutionary history.

A Creation Model Perspective on Mitochondria

So, as a creationist, how do I make sense of the evidence for the endosymbiont hypothesis?

Instead of focusing my efforts on refuting the endosymbiont hypothesis, here, I take a different approach. I maintain that it is reasonable to view eukaryotic cells as the work of a Creator, with the shared similarities between mitochondria and bacteria reflecting common design rather than common descent.

However, to legitimately interpret mitochondrial origins from a creation model perspective, there must be a reason for the biochemical similarities between mitochondria and bacteria. Previously, I wrote about discoveries that provide a rationale for why mitochondria have their own genomes. (See “Resources.”) Thanks to recent research advances, an explanation now exists for why the mitochondrial inner membranes harbor cardiolipin.

Cardiolipin’s Function

Previous studies identified close associations between cardiolipin and a number of proteins found in the mitochondrial inner membrane. These proteins play a role in harvesting energy for the cell to use. Compared to other lipid components found in the inner membrane, cardiolipin appears to preferentially associate with these proteins. Evidence indicates that cardiolipin helps to stabilize the structures of these proteins and serves to organize the proteins into larger functional complexes within the membrane.2 In fact, several studies have implicated defects in cardiolipin metabolism in the onset of a number of neuromuscular disorders.

The work of the Cambridge University investigators adds to this insight. These researchers were using computer simulations to model the interactions between cardiolipin and a protein complex called F1-F0 ATPase. Embedded within the inner membrane of mitochondria, this complex is a biomolecular rotary motor that produces the compound ATP—an energy storage material the cell’s machinery uses to power its operations.

Like other proteins found in the inner membrane, cardiolipin forms a close association with F1-F0 ATPase. However, instead of permanently binding to the surface of the protein complex, cardiolipin dynamically interacts with this membrane-embedded protein complex. The researchers think that this dynamic association and the unusual chemical structure of cardiolipin (which gives it the flexibility to interact with a protein surface) are critical for its role within the mitochondrial inner membrane. As it turns out, cardiolipin not only stabilizes the F1-F0 ATPase complex (as it does for other inner membrane proteins), but it also lubricates the protein’s rotor, allowing it to turn in the viscous cell membrane environment. Also, its unique structure helps move protons through the F1-F0 ATPase motor, providing the electrical power to operate this biochemical motor.

The bottom line: There is an exquisite biochemical rationale for why cardiolipin is found in mitochondrial inner membranes (and bacterial membranes). In light of this new insight, it is reasonable to view the shared similarities between these organelles and bacteria as reflecting common design—the product of the Creator’s handiwork. Like most biological systems, this organelle appears to be designed for a purpose.

Resources
Why Do Mitochondria Have DNA?” by Fazale Rana (article)
Mitochondrial Genomes: Evidence for Evolution or Creation?” by Fazale Rana (article)
Complex Protein Biogenesis Hints at Intelligent Design” by Fazale Rana (article)
Archetype or Ancestor? Sir Richard Owen and the Case for Design” by Fazale Rana (article)
Nanodevices Make Megascopic Statement” by Fazale Rana (article)

Endnotes

  1. Anna Duncan, Alan Robinson, and John Walker, “Cardiolipin Binds Selectively but Transiently to Conserved Lysine Residues in the Rotor of Metazoan ATP Synthases,” Proceedings of the National Academy of Sciences USA 113 (August 2016): 8687–92, doi:10.1073/pnas.1608396113.
  2. Giuseppe Paradies et al., “Functional Role of Cardiolipin in Mitochondrial Bioenergetics,” Biochimica et Biophysica Acta—Bioenergetics 1837 (April 2014): 408–17, doi:10.1016/j.bbabio.2013.10.006.
Reprinted with permission by the author
Original article at:
https://www.reasons.org/explore/blogs/the-cells-design/read/the-cells-design/2016/11/23/can-a-creation-model-explain-the-origin-of-mitochondria

Science News Flash: Has the Last Universal Common Ancestor Been Identified?

sciencenewsflashhasthelastuniversal

BY FAZALE RANA – JULY 28, 2016

Researchers from Germany made headlines by announcing that they are one step closer to identifying LUCA (the last universal common ancestor)—the single-celled organism that anchors the evolutionary tree of life.1

Because an organism’s genes reflect its environment, these researchers attempted to partially reconstruct LUCA’s genome. They reasoned that this reconstruction would tell them something about LUCA’s complexity and lifestyle.2 To accomplish this task, the researchers searched 6.1 million protein-coding genes found in archaeal and bacterial genomes for those with a special type of history (that is, they searched for universal, monophyletic genes).

They identified 355 types of genes that fit their criteria. A few of the genes appear to be involved with essential biochemical operations such as DNA replication, transcription, and translation. On the other hand, most of the 355 genes play highly specialized roles that reflect a thermophilic lifestyle. For example, they discovered an enzyme called reverse gyrase that is only found among microbes that live in high-temperature environments. They also discovered enzymes that are part of a metabolic route called the Wood-Ljungdahl pathway. This pathway uses molecular hydrogen as an electron donor, and carbon dioxide as an electron acceptor. The hydrogen had to come from a geological source. On this basis, the German scientists concluded that LUCA lived in a hydrothermal vent environment, providing a ready source for this life-giving gas.

The researchers also discovered that this microbe was able to: 1) fix nitrogen from the environment, incorporating this atom into it’s biomolecules; 2) lived in an anaerobic environment (devoid of oxygen); but 3) didn’t seem to have the ability to make amino acids. The investigators think that LUCA, though primitive, may have had more than 355 genes. If the investigators relax their search requirements a bit, they estimate that LUCA may have had nearly 575 genes.

The German research team argued that not only was LUCA a thermophile, but that the origin of life occurred at hydrothermal vents.

Have these researchers provided us with a key insight into LUCA’s identity? Have they identified the locale for the origin of life?

Not necessarily. Here are some points to consider:

In other words, there are good scientific reasons to question the high-temperature origin of life and the thermophilic identity of LUCA. And given the apparent complexity of LUCA, there is a strong basis to question evolutionary scenarios for life’s start.

In spite of the headlines, scientists have no true understanding of how chemical evolution could have produced the first life on Earth.

Resources
Too Hot to Handle” by Fazale Rana (Article)
Some Like It Hot—First Life Did Not” by Fazale Rana (Article)
Sea Vents Closed as Life-Origin Site” by Fazale Rana (Article)
Biochemists Ask, ‘How Low Can Life Go?’” by Fazale Rana (Article)
Origins of Life by Fazale Rana and Hugh Ross (Book)
Creating Life in the Lab by Fazale Rana (Book)

Endnotes

  1. Madeline C. Weiss et al., “The Physiology and Habitat of the Last Universal Common Ancestor,” Nature Microbiology 1 (July 2016): 16116, doi:10.1038/NMICROBIOL.2016.116; James O. McInerney, “Evolution: A Four Billion Year Old Metabolism,” Nature Microbiology 1 (July 2016): 16139, doi:10.1038/NMICROBIOL.2016.139.
  2. Scientists think that LUCA was a prokaryotic, single-celled microbe.
Reprinted with permission by the author
Original article at:
https://www.reasons.org/explore/blogs/the-cells-design/read/the-cells-design/2016/07/28/science-news-flash-has-the-last-universal-common-ancestor-been-identified