Ancient fossils maybe giant bacteria, not eggs and embryos


This 2018 video is called Evolution from Bacteria to Humans.

From the University of Southern California:

Oldest animal fossils may have been bacteria

Nature study rearranges geological record

The oldest-known animal eggs and embryos, whose first pictures made the cover of Nature in 1998, were so small they looked like bugs – which, it now appears, they may have been.

This week, a study in the same prestigious journal presents evidence for reinterpreting the 600 million-year-old fossils from the Precambrian era as giant bacteria.

The discovery “complicates our understanding of microfossils thought to be the oldest animals,” said lead author Jake Bailey, a graduate student in earth sciences at the University of Southern California.

Bailey made his discovery by combining two separate findings about Thiomargarita, the world’s largest known living bacterium.

In 2005, Thiomargarita discoverer Heide Schulz, from the University of Hannover in Germany, showed that the bacterium promotes deposition of a mineral known as phosphorite.

The fossils identified as eggs and embryos in 1998 came from southern China’s Doushantuo Formation, which is rich in phosphorite.

The source for the rare mineral was unknown. Bailey wondered if an ancient relative of Thiomargarita might have been involved.

“The idea is that these bacteria were causing these phosphorite deposits to form,” Bailey said.

Also in 2005, University of Georgia marine biologists Samantha Joye and Karen Kalanetra, who are co-authors on Bailey’s study, found that Thiomargarita can multiply by reductive cell division, a process rare among bacteria but typical of animal embryos.

Bailey knew that the fossils had been identified as embryos in part because they showed evidence of reductive cell division.

Then he thought again about the phosphorite deposits.

“When I put those two pieces together, I said … perhaps they’re not animal embryos at all.”

Bailey and his co-authors compared the size and geometrical properties of the Doshuanto fossils and modern Thiomargarita bacteria – they were nearly identical.

Coupled with the presence of phosphorite, the result pointed strongly to ancient Thiomargarita activity.

Bacteria and Archaea must have evolved from the putative Last Universal Common Ancestor (LUCA). One hypothesis is that this happened because the cell membrane in LUCA was an unstable mixture of lipids. Now, scientists have created such a life form with a mixed membrane and discovered it is in fact stable, refuting this hypothesis: here.

4 thoughts on “Ancient fossils maybe giant bacteria, not eggs and embryos

  1. Pingback: University Update

  2. Thousands of new marine microbes discovered
    Thu Oct 4, 2007 4:43pm EDT

    By Julie Steenhuysen

    CHICAGO (Reuters) – Scientists have uncovered thousands of marine microbes — including never-before-seen bacteria — thriving deep in the sea near cracks in the Earth’s crust where warm fluids and cold sea water mix, U.S. researchers said on Wednesday.

    Using new DNA sequencing techniques, the researchers have identified as many as 37,000 different kinds of bacteria huddled near two hydrothermal vents on an underwater volcano off the Oregon coast.

    “Many of these bacteria had never been reported before,” said Julie Huber of the Marine Biological Laboratory in Woods Hole, Massachusetts, whose study appears in the journal Science.

    Huber and colleagues at the University of Washington’s Joint Institute for the Study of Atmosphere and Ocean took samples from two hydrothermal vents on the Pacific deep-sea volcano, Axial Seamount.

    “You’ve got hot fluids that have things in it like hydrogen gas and sulfur, which are not things you find in abundance in regular sea water. They’re mixing with this cold, oxygen-rich sea water.

    “It creates a lot of neat niches for life,” Huber said in a telephone interview.

    CENSUS OF MARINE MICROBES

    Her research is part of an international effort to create a census of marine microbes, which make up as much as 90 percent of the total ocean biomass by weight.

    Huber and colleagues focused their study on a gene that is common to all microbes that is essential for protein synthesis.

    “You have it. I have it. Even your dog has it. And microbes have it,” Huber said.

    Her team looked at 900,000 of these genes, a massive undertaking that allowed her to arrive at an estimate of the number of microbes in the sample.

    They found the samples were dominated by epsilon Proteobacteria, which are found in many different places on Earth including the human gut, and have been known to lurk around hydrothermal vents.

    And while the two samples were taken just a few miles (kilometers) apart on the same volcano, they have totally different chemistries and population structures.

    “We found they were completely different types of epsilon at the two different vents,” she said.

    “We think it is because of the different geochemistries of the two different vents and the microbes have adapted to the two different environments.”

    Huber said her work will help serve as a baseline for understanding of the microbes currently in the ocean.

    “A lot of people don’t realize that microbes make living on Earth possible. They produce the oxygen we breathe. They have been on this planet for 3.5 billion years,” she said.

    “We really need to understand who is there and what they’re doing because things are changing, and they’re changing rapidly, and we don’t even know what the baseline is supposed to be”

    And without that, she said, “We’re not going to know if things are changing.”

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  3. Pingback: World’s oldest animal discovery in Russia | Dear Kitty. Some blog

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