New Forms of Life

Late last year, it was reported that scientists had discovered new forms of life inside human bodies. They don’t match anything biology has classified.

A new class of RNA molecules was discovered inside bacteria that lives in the human body. They are circular genetic structures called obelisks. They differ from known viruses and bacteria. They appear to represent an unclassified category of RNA.

The discovery came from an analysis of genetic material obtained from microbial communities inside humans. Obelisks may be present across global populations. But their exact function is unclear.

These RNA entities are simple. They don’t encode proteins. They don’t form protective protein shells. They consist of short loops of RNA that replicate, although how remains a mystery.

More than 3,000 types of obelisks have been identified using computational tools designed to detect circular RNA structures in large genomic libraries. Researchers detected closed-loop RNA structures that lack protein-coding regions. As such, the molecules resemble viroids, which are also non-coding, circular RNAs. However, viroids infect plants, but obelisks are only found in human-associated bacteria.

Many of the obelisks are embedded in bacterial genomes, which suggests they may have adapted to specific bacterial hosts. No immediate health effects have been linked to obelisks, but their residence in bacteria that support digestion, immunity, and other function point to future research on the matter.

Obelisks don’t conform to definitions of viruses, plasmids, or other mobile genetic elements. They fall outside microbial categories.

The implications extend into evolutionary biology, particularly in the origins of RNA-based life. Some theories suggest early life may have relied solely on self-replicating RNA. Obelisks could offer insight into these early evolutionary stages.

Obelisks do exhibit genetic diversity. Different variants appear in specific regions of the body. This may reflect host-specific adaptations. It is unknown if they have any regulatory or ecological function in the microbiome.

There is scientific interest in non-coding and circular RNAs, which play roles in gene regulation and cellular function in plants and animals. Obelisks are different in that they seem to operate independently, with no participation in protein synthesis or cellular regulation.

The discovery shows that modern metagenomic-sequencing can detect molecular entities that don’t fit into established classifications.

Scientists expect further discoveries of novel RNA forms with unknown roles. It is not known if obelisks are ancient relics or modern molecular parasites. Research continues.

 

https://www.msn.com/en-us/health/medical/scientists-discover-new-forms-of-life-inside-human-bodies-that-don-t-match-anything-biology-has-classified/ar-AA1T7ARd?ocid=hpmsn&cvid=695189ccf8ea491b9920af677646366e&ei=56

Perseverance Found a Rock

NASA’s Perseverance rover has combed Jezero Crater for years, looking for traces of ancient microbes. However, its most interesting find is a rock. Specifically, a rock that does not belong on Mars. This discovery exposes a new kind of mystery. One about what reaches the Red Planet and how those arrivals might complicate the search for biology.

Perseverance was sent to Mars to look for chemical whispers of long-vanished microbes. Its tools were meant for sedimentary targets, not stray boulders that possibly fell from deep space. Yet those same instruments can be used on out-of-place boulders to study a broader aspect of planetary history.

The object is a compact, sculpted mass that is definitely not part of the dusty basalt and sediment of Jezero Crater. Its texture and metallic sheen suggest it was not carved by Martian wind or water.

Imaging and analysis imply it might be a possible meteorite. The surface is pitted and fused in ways consistent with a plunge through an atmosphere. One meteorite on a planet that has been bombarded by them for billions of years might not sound important. Jezero Crater once held a lake with a river flowing away from it. These conditions provide the best chances for biosignatures. Dropping a rock rich in iron into that setting complicates the story.

Scientists had been waiting for this. Given how common iron nickel meteorites are on Earth, they were baffled that Perseverance had not seen any such meteorites in the crater. Until now. The find fills a gap in expectations and demands a recalibration of how meteorites weather, survive, and appear on the Martian surface.

Perseverance’s team is operating at the edge of what remote sensing can do. It uses subtle shifts in mineralogy to reconstruct ancient environments. When the team labels a new object as totally alien to the Red Planet, that judgement is based on years of comparative study. The meteorite is visually strange, but also chemically and texturally different from the Jezero rocks.

The meteorite has been referred to as “Phippsaks,” a nickname that now anchors a growing archive of images, spectra, and contextual observations.

The meteorite discovery arrived as scientists were rethinking the Martian atmosphere. Perseverance’s microphone has detected electric sparks on Mars, which hint at active electrical processes in the thin air. The Martian sky may not be as quiet or simple as once thought. If dust storms and atmospheric conditions are more dynamic than thought, those conditions will influence how meteorites burn, fragment, and land.

The meteorite is interesting, but Perseverance was sent to search for signs of ancient life. A sample from an ancient riverbed may contain the clearest chemical hints of past biology.

Against that backdrop, the meteorite is likely sterile metal, battered by radiation during its journey through space. Yet it can deliver elements and compounds that alter the chemistry where microbes might have once lived. A foreign rock landing in a once habitable delta is another layer of complexity that must be taken into account.

 

https://www.msn.com/en-us/news/technology/perseverance-spotted-a-mars-mystery-and-nasa-is-treating-it-as-massive/ar-AA1T8rnm?ocid=hpmsn&cvid=695189ccf8ea491b9920af677646366e&ei=85

Life on Mars?

Do you believe there was past life on Mars? Here’s what new NASA evidence indicates.

Dry, cold and barren. Mars doesn’t seem like a haven for life—at least not the kind humans are familiar with.

Scientists have wondered for decades if microbial life could have inhabited Mars in the distant past. One study, based on data collected by NASA’s Curiosity rover, is peeling back a layer of the mystery. Researchers measured the isotopic composition of carbon-rich minerals found in Gale Crater. This region is laced with dried rivers and gullies and was explored by the rover.

The findings Curiosity sent to Earth were not optimistic about the potential for life above ground. But that doesn’t rule out the possibility of an underground biosphere or even a surface biosphere that began and ended before the carbonates were formed.

This suggests two possible ways carbon-rich minerals could have form at Gale crater: a series of alternating wet and dry periods or salty-ice conditions. These two climate scenarios could be called ‘bleak’ and ‘bleaker’ when it comes to supporting life.

In an environment that swings from wet to dry, the region would shift from more habitable to less habitable. In the frigid temperatures near Mars’ equator, that environment would be hostile for life because most water would be frozen and inaccessible for chemistry or biology. Plus, what water was there was extremely salty, not pleasant for life.

This isn’t the first time scientists have theorized these climate scenarios for ancient Mars. Previous computer models have indicated these conditions before, but now they have isotopic evidence from Martian rocks.

Scientists have sought life on Mars since the first spacecraft touched down there in 1976. Mounting evidence from robotic explorers has shown the Red Planet to have been warmer and wetter, perhaps more than 3 billion years ago.

The Perseverance rover discovered a spotted rock with compelling signs of ancient dead Martian life, but a sample would need to be shipped to Earth for confirmation. A research team also reported evidence of a vast ocean of water below the planet’s surface. On Earth, where there’s water, there’s often life.

Scientists are interested in Mars’ carbon-rich rocks because they can hold clues about the environment in which they formed, such as the temperature and acidity of the water, and ingredients in the water and air.

The sampled rocks indicate lots of evaporation, suggesting a climate that could only support transient liquid water—that is, ice that melts when temperatures rise and the surface pressure is right.

The heavy isotope values in the rocks are much higher than what’s seen on Earth. They are the heaviest carbon and oxygen isotope values recorded for any Martian materials. Although evaporation can cause oxygen isotope changes on Earth, the changes in the Martian samples were two to three times greater.

But this doesn’t negate the possibility of life. Mars has a network of deep caves formed by ancient volcanic vents. Within the caves could be liquid water, traces of long-deceased bacteria or fungi, or perhaps even existing microbial life.

Caves can host complex ecosystems, including extremophiles that munch on rocks and convert the material into energy for life. So, many astrobiologists want to go spelunking on Mars. Would you like to join them?

 

https://www.msn.com/en-us/news/technology/past-life-on-mars-here-s-what-new-nasa-evidence-points-to/ar-AA1rWIgJ?ocid=hpmsn&cvid=5432d20e554e4f3ea664d26edcf277ee&ei=74

Cambrian Period

The Cambrian Period lasted from 541 to 485 million years ago. At the beginning of this time period, the small unicellulars that represented most life on Earth became more complex and multicellular. They also diversified quite rapidly, bringing forth the first representatives of all modern animal phyla. Indeed, there is strong evidence that all animals evolved from a single common ancestor.

Life prospered in the oceans, but the land is thought to have been relatively barren, with nothing more complex than a microbial soil crust or biofilm. A few molluscs may have emerged to browse on that biofilm, but the continents were probably dry and rocky. The global supercontinent Pannotia had just broken up during the early part of the period, and the new continents were mostly flanked by shallow seas, which were relatively warm. Polar ice was absent for much of this period.

Most land masses were clustered in the Southern Hemisphere during this period, but were drifting north. During the early portion of the Cambrian, the supercontinent of Gondwana went through some large, high-velocity rotational movements.

Trilobites (I wrote about them in an earlier post) were rampant during the Cambrian period. Possibly this was because without any sea ice, the sea level was high, which meant large areas of the continents were flooded in warm shallow seas, which is ideal for sea live. But the sea levels did fluctuate somewhat, suggesting there were ‘ice ages’, possibly meaning pulses of expansion and contraction of a south polar ice cap. Although the beginning of the period was cold, the average temperature during the Cambrian was 7° Celsius warmer than today.

Even so, trilobites were not the dominant species, as was once thought. It seemed they were, because they had hard external shells that were easy to fossilize, much easier than the thin chitinous shells of other arthropods, and so trilobite fossils were much easier to find by today’s paleontologists.

The Cambrian period is often referred to as ‘the Cambrian Explosion’, indicating a huge increase in the variety and diversity of life forms. But it seems (to me) that it might be better to think of it as ‘the Period of Great Changes’. At the start of the Cambrian, new creatures with new behaviors and lifestyles destroyed the biofilm that covered the sea floor, so all the creatures (from the previous time period) who depended on that biofilm died out.

Around 515 million years ago, the number of species dying out was larger than the number of new species coming into existence. 500 million years ago, the oceans saw a big drop in the oxygen content, and at the same time, the level of toxic hydrogen sulfide increased. Either of these events alone could produce extinctions, so imagine what happened when they came in together.

Where would hydrogen sulfide have come from? There are a few ways nature makes it, including anerobic digestion by certain biofilms in the absence of oxygen. I can’t rule that one out, but I’m somewhat more inclined to ‘blame’ volcanoes, which also produce it, probably in larger quantities and certainly can do it in oceans. Also, the heat given off by the volcano(es) would tend to drive oxygen out of the water. So, was there a series of huge volcano events 500 million years ago? I don’t know. It seems possible.

And there we have the Cambrian period in a nutshell. No fascinating dinosaurs to study, but the thought of a spinning Gondwana certainly has my attention.

https://en.wikipedia.org/wiki/Cambrian

https://en.wikipedia.org/wiki/Hydrogen_sulfide

Cold and Salty

When you and I think of someplace nice to live, we probably aren’t thinking “really cold and super salty”. And yet, there are organisms that do.

After 18 months of gathering cold salty water from remote lakes located in Antarctica - including during the extreme winter - scientists discovered... microbes! One location was Deep Lake, whose water is so salty, it remains unfrozen down to -20°.

At least one strain of microbes contained plasmids, which are small molecules of DNA which can replicate independently in a host cell and often contain useful genes. A plasmid can also grab a piece of DNA from the host cell and incorporate it in itself. They’re certainly complicated, for being so tiny.

Viruses have a protective protein coat that helps them invade unsuspecting cells. Once inside, the virus forces the cell to replicate virus DNA and package it into protein shells, which are pushed out of the ‘nest’ to find their own host cell and repeat the process. Most viruses damage the host cell.

One particular plasmid - called pR1SE - is so much like a virus, the scientists weren’t sure how to classify it. Before this Antarctica discovery, plasmids were known to move from cell to cell when 2 cells were touching, or they wandered around as a piece of naked DNA. However, pR1SE must have thought it too cold in Antarctica to wander around naked, so it had developed a coating of proteins that could attach to a cell wall. Once attached, the protein coat would produce buds (called vesicles), and those buds broke off, taking bits of plasmid DNA to do the same with other cells of the same species.

Virus? Plasmid? This pR1SE version seemed to be something in between. In fact, having discovered this mechanism, scientists are wondering if possibly viruses are ‘more advanced’ versions of plasmids.

Another microbe found in those hypersaline lakes is a ‘cannibal virus’, or virophage, the 3rd virophage ever discovered. This type of virus only infects cells that are already infected with a ‘regular’ virus. As the regular virus uses the cell’s mechanisms to reproduce copies of itself, the virophage inserts its genome into the virus, thus getting the virus to reproduce virophage DNA. The number of copies of the regular virus is greatly reduced, so damage is reduced.

There’s plenty of tiny life in them there super-cold, super-frigid lakes, from things that hardly seem like life (regular plasmids), to something slightly more advanced (pR1SE), through another advancement (viruses) and right to something (virophage) that can try to limit the damage done by the prior version (viruses). Who could have guessed that life in Antarctica would be so complicated?

So, let’s take a lesson from this. Life is complicated. If you are creating a new planet or even just a new continent, try to make the life cycle complicated. I have problems with a planet of sand that produces butterflies and giant worms, and that’s all. If the giant worms only have butterflies to eat, how do they get so big? And what do the butterflies eat?

https://phys.org/news/2017-08-antarctic-salt-loving-microbes-insights-evolution.html

http://www.sciencealert.com/cannibal-viruses-in-antarctica

https://www.newscientist.com/article/2144518-antarctic-mystery-microbe-could-tell-us-where-viruses-came-from/