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/
