Saturday, February 7, 2015

Absence of evolution? The Discover of  microorganism that has not evolved over millions of years.

The new discovery of two microbial biota in the deep waters of Turee Creek and Duck Creek in Western Australia, opens a new window on the early history of life,  to discover bacteria that can oxidize sulfur with a length of 2.3 billion years (2.3 Ga).

These bacteria were found permineralized in silica,  formed shortly after the great oxidation (2.4 to 2.2 Ga)  so these two biota can get an answer to what happened in the Precambrian era where increasing environmental oxygen caused an increase in the production of sulfate and nitrate metabolically usable.

But despite these two biota can provide information on the great oxidation on Earth  and how amazing is that comparing microbial morphology of fossil bacteria, also habitat and bacteria organization of "modern" sulfur found on the coast of Chile revealed that these two biota were exactly the same,  but with the news that the newly discovered had 2.3 Ga.

Similarities in their habitat

Fig. 1. Fabric biota from the Precambrian era. (A-C) Duck Creek 1. 8 Ga; (D-F) Turee Creek 2.3 Ga (Schopf et al., 2015).

These ecosystems biota are characterized by the presence of large bacterial populations that have the ability to metabolize sulfur,  also by a low content of dissolved oxygen, in some parts of the subsurface of the community, is essentially zero.  Usually comprise two regions: an anoxic zone below the resting surface consisting similar to an interlaced network of randomly oriented long fabric and commonly microorganisms anaerobic filamentous 10 microns in diameter.

Similarities in morphology and physiology

Fig. 2. Morphological Comparison between "modern" bacteria with fossil bacteria obtained from Turee Creek (2.3 Ga) and Duck Creek (1.8 Ga) (Schopf et al., 2015).

The marked similarities in morphology microbial,  habitat and community organization Precambrian their modern counterparts bacteria show a great adaptation to its environment under the seabed,  which has remained essentially unchanged for billions of years.

But really seems incredible that life in this habitat has not changed for almost half of the history of the earth when we see that evolution is evident,  although the apparent stagnation of two billion years of duration of the mentioned ecosystems relating to the sulfur cycle,  is consistent with Darwinian hypothesis which states that if there is a change in the Physical-Biological environment of a well-adapted ecosystem,  all biotic components should remain unchanged, i.e., the key to biology is not evolve unless cause changes in the physical or biological environment.

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Sunday, February 1, 2015

Methanogens in Mars?

Excitement over the Curiosity rover’s recently reported detection of a ‘spike’ in localized atmospheric methane – persisting over a couple of months – is well founded. It’s possible that this represents a very real clue to past or present life on Mars. Or rather, life in Mars. The great majority of methane that we find here on Earth (whether in the air or in subsurface deposits) has a biological origin. This methane is generated by methanogenesis, a metabolic process that seems to be confined to members of the domain Archaea.

There’s more than one chemical pathway for making methane, but the most obvious is the combination of carbon dioxide with molecular hydrogen, and that’s precisely the reaction that a slew of methanogenic archaea latch onto. Molecular hydrogen is a potent source of chemical energy, and other organisms such as sulfate-reducing bacteria also gobble it up. So where do they find that hydrogen?

Methanogens. Credit: Maryland Astrobiology Consortium, NASA, and STScI
One source is where rock and water sit together. Radioactivity from rocks laced with elements like uranium can break up water molecules (the process of radiolysis), and the geochemical process of serpentization also spits out molecular hydrogen in abundance. Active hydrothermal vent systems on ocean beds are one environment where hydrogen is readily made, and methanogenic organisms thrive there. Places like these are, in relative terms, packed with chemical energy that life can exploit, and does.

Now a new study by Lollar, Onstott, Lacrampe-Couloume & Ballentine reported in Nature (2014) suggests that the deep (5km) continental zones could indeed be a major producer of hydrogen. Specifically, the most ancient Precambrian continental subsurface (rock older than about 540 million years), could generate molecular hydrogen at a rate 40 to 250 times higher than previously thought – a production on par with that associated with the much younger marine lithosphere. This Precambrian material exists in about 70% of the Earth’s continental area, and could contain as much water as all surface rivers, swamps, and lakes.

The conclusion is that the global production of molecular hydrogen needs an upward revision and, most critically, at least half of that is coming from the deep, ancient continental subsurface – which is not dry, not inert, and seems to be filled with life.

Connecting the discoveries of methane on Mars could give us an idea of how the Earth was in its earliest stages. It could also give us a clue as to where to look to find microorganisms based on the known methanogens in Earth.