Dark matter, the strange anti-material counterpart to the stuff of the Universe as we know it, remains one of the greatest mysteries of modern space and cosmology. Strangely, in spite of what we can perceive about it’s role in the greater galactic scheme (or perhaps more appropriately, what we can’t perceive about it, aside from its gravitational effects on surrounding matter), there is really more that remains a mystery to this odd stuff than we probably even realize. It’s literally as though some of the fundamental secrets our Universe maintains are hidden right before us, though obscured from human perception.
Much the same as dark matter can be best perceived more easily by its effects on the things around it, a new study suggests that there may be kinds of life on Earth which, though presumed to exist, may have remained “hidden” in ways that could be likened to dark matter.
A recent article appearing in New Scientist seeks to define just how this might have occurred, describing the efforts of a group of scientists who believe a fourth variety of life may exist, in addition to the known bacteria, archaea and eukaryotes present among us:
To probe life’s dark matter, Eisen, Craig Venter of the J. Craig Venter Institute in Rockville, Maryland, and their colleagues have resorted to a relatively new technique called metagenomics. This can “sequence the crap out of any DNA samples”, whether they are collected from the environment or come from lab cultures, says Eisen.
When Eisen and Venter used the technique on samples collected from the Global Ocean Sampling Expedition, they found that some sequences belonging to two superfamilies of genes – recA and rpoB – were unlike any seen before.
“What are they from?” Eisen wondered of the new discovery. The genes in question appeared to belong to some kind of organism, but as to its actual identity, little more than speculation exists. One idea Eisen and his team have put forth is that the genes belong to some “unusual virus,” if not “a totally new branch in the tree of life.” But what exactly could this mean?
Let’s consider whether the “hidden” genes could have been some variety of virus. It would be interesting indeed if this were the case, though perhaps a bit frightening: after all, are there viruses on Earth that might exist, though they remain somewhat secretive from us? Furthermore, could this suggest that these simple organisms could present dangers to humans in various instances (think along the lines of “mystery illnesses” that crop up out of nowhere from time to time, ravaging their victims with largely untreatable symptoms). Or, on the other hand, what if something unique of this sort only appeared to be a virus?
For instance, the mimivirus, as New Scientist’s Colin Barras points out, is presently considered the largest known virus. However, this particularly large virus, sometimes known to be a factor in the manifestation of pneumonia, has actually been suggested in certain scientific circles to represent a new domain of life altogether. This is because the mimivirus contains a number of genes specific to cellular organisms, placing it on the proverbial razor’s edge between things considered “living” and “non-living.” What it lacks, in addition to homeostasis and general response to stimuli that other cells exhibit, are the genetic processes required for creation of ribosomes, which use amino acids to create proteins and process energy for living cells. Hence, the mimivirus, though very similar to an order of life unto itself, maintains one very vampiric trait in order to survive: it is forced to have to leech energy off of other “host” cells. Thus, it remains a virus, for now.
Should more definitive classifications ever result from continuing studies of these and other occupants of the microscopic world, we could one day have four–or possibly five or more–fundamental classifications of life. Altogether, it appears yet again that in spite of our continued search for life elsewhere in the cosmos, we’re still finding new forms of life all the time right here on Terra Firma.