* Astronomy

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" - lead author Jake Bailey, a graduate student in earth sciences at USC College.

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

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Tiny formless particles in water solution take on a well-ordered and functional structure as soon as they come into contact with nanoparticles of silica. A unique breakthrough by researchers at Linköping University in Sweden creates new potential in medicine and biochemistry and at the same time provides a new piece of the puzzle in theories about the origins of life.
Normally, inorganic materials like silica are unwelcome in biological systems, since they disrupt the form and function of proteins.

"We wanted to reverse the thinking and try to design proteins that take on their function only after encountering an inorganic surface" - Bengt-Harald Jonsson, professor of molecular biotechnology.

He directs the research team that is now presenting its findings in Angewandte Chemie.
The team designed a peptide (a short protein) with a specific distribution of positive charges. The peptide was mixed into a solution of spherical silica particles, about 9 nanometers (billionths of a meter) across. When the peptide was free in the solution it had no structure whatsoever, but when it connected with the negatively charged silica ball it assumed the form of a helix. The result was a complex of a silica particle and a functional protein.
When the researchers added amino acids to their peptide, the complex took on the properties of a catalyst, a function similar to that of enzymes in living cells.

The method has several possible fields of application:
recognition of organic molecules
catalysing of chemical reactions with precise control
target-seeking particles for medical uses

But the Linköping University scientists’ successful experiment may also shed light on the eternal question of the origin of life. Particles of clay containing silica in the ‘primeval soup’ may have attracted unstructured peptides with amino acids attached and given rise to the first functional proteins.

"We know that RNA (which plays a decisive role in the transfer of information in cells) can bind with clay particles whose surfaces have negative charges. The probability of peptides with amino acids having formed well-defined structures with the clay at an early stage of development is considerably greater, since they are more diversified than RNA is" - Bengt-Harald Jonsson.

Source: Linköping University

Two and a half billion years ago, when our evolutionary ancestors were little more than a twinkle in a bacterium's plasma membrane, the process known as photosynthesis suddenly gained the ability to release molecular oxygen into Earth's atmosphere, causing one of the largest environmental changes in the history of our planet. The organisms assumed responsible were the cyanobacteria, which are known to have evolved the ability to turn water, carbon dioxide, and sunlight into oxygen and sugar, and are still around today as the blue-green algae and the chloroplasts in all green plants.
But researchers have long been puzzled as to how the cyanobacteria could make all that oxygen without poisoning themselves. To avoid their DNA getting wrecked by a hydroxyl radical that naturally occurs in the production of oxygen, the cyanobacteria would have had to evolve protective enzymes. But how could natural selection have led the cyanobacteria to evolve these enzymes if the need for them didn't even exist yet?
Now, two groups of researchers at the California Institute of Technology offer an explanation of how cyanobacteria could have avoided this seemingly hopeless contradiction. Reporting in the December 12 Proceedings of the National Academy of Sciences (PNAS) and available online this week, the groups demonstrate that ultraviolet light striking the surface of glacial ice can lead to the accumulation of frozen oxidants and the eventual release of molecular oxygen into the oceans and atmosphere. This trickle of poison could then drive the evolution of oxygen-protecting enzymes in a variety of microbes, including the cyanobacteria. According to Yuk Yung, a professor of planetary science, and Joe Kirschvink, the Van Wingen Professor of Geobiology, the UV-peroxide solution is "rather simple and elegant."

"Before oxygen appeared in the atmosphere, there was no ozone screen to block ultraviolet light from hitting the surface. When UV light hits water vapour, it converts some of this into hydrogen peroxide, like the stuff you buy at the supermarket for bleaching hair, plus a bit of hydrogen gas. Normally this peroxide would not last very long due to back-reactions, but during a glaciation, the hydrogen peroxide freezes out at one degree below the freezing point of water. If UV light were to have penetrated down to the surface of a glacier, small amounts of peroxide would have been trapped in the glacial ice" - Joe Kirschvink.

This process actually happens today in Antarctica when the ozone hole forms, allowing strong UV light to hit the ice.
Before there was any oxygen in Earth's atmosphere or any UV screen, the glacial ice would have flowed downhill to the ocean, melted, and released trace amounts of peroxide directly into the sea water, where another type of chemical reaction converted the peroxide back into water and oxygen. This happened far away from the UV light that would kill organisms, but the oxygen was at such low levels that the cyanobacteria would have avoided oxygen poisoning.

"The ocean was a beautiful place for oxygen-protecting enzymes to evolve. And once those protective enzymes were in place, it paved the way for both oxygenic photosynthesis to evolve, and for aerobic respiration so that cells could actually breathe oxygen like we do" - Joe Kirschvink.

The evidence for the theory comes from the calculations of lead author Danie Liang, a recent graduate in planetary science at Caltech who is now at the Research Center for Environmental Changes at the Academia Sinica in Taipei, Taiwan.
According to Liang, a serious freeze-over known as the Makganyene Snowball Earth occurred 2.3 billion years ago, at roughly the time cyanobacteria evolved their oxygen-producing capabilities. During the Snowball Earth episode, enough peroxide could have been stored to produce nearly as much oxygen as is in the atmosphere now.
As an additional piece of evidence, this estimated oxygen level is also sufficient to explain the deposition of the Kalahari manganese field in South Africa, which has 80 percent of the economic reserves of manganese in the entire world. This deposit lies immediately on top of the last geological trace of the Makganyene Snowball.

"We used to think it was a cyanobacterial bloom after this glaciation that dumped the manganese out of the seawater. But it may have simply been the oxygen from peroxide decomposition after the Snowball that did it" - Danie Liang.

In addition to Kirschvink, Yung, and Liang, the other authors are Hyman Hartman of the Centre for Biomedical Engineering at MIT, and Robert Kopp, a graduate student in geobiology at Caltech. Hartman, along with Chris McKay of the NASA Ames Research Centre, were early advocates for the role that hydrogen peroxide played in the origin and evolution of oxygenic photosynthesis, but they could not identify a good inorganic source for it in Earth's precambrian environment.

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Frenzied star-making in the Milky Way Galaxy starting about 2400 million years ago had extraordinary effects on life on Earth. Harvests of bacteria in the sea soared and crashed in a succession of booms and busts, with an instability not seen before or since. According to new results published by Dr. Henrik Svensmark of the Danish National Space Centre in the journal Astronomische Nachrichten, the variability in the productivity of life is closely linked to the cosmic rays, the atomic bullets that rain down on the Earth from exploded stars. They were most intense during a baby boom of stars, many of which blew up.

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