Making new evolutionary innovations: bacteria create soil (Introduction)

by David Turell @, Tuesday, May 05, 2020, 02:07 (28 days ago) @ David Turell

It is well known lichens break down rock, but bacteria are also very active in the process:

https://blogs.scientificamerican.com/artful-amoeba/scientists-waited-two-and-a-half-yea...

"It’s long been assumed that life is somehow involved (on Earth, there is very little in which life is not involved), and scientists have demonstrated that it is theoretically possible. But no one had ever actually observed this in common types of iron-silicate continental rocks, likely due to the distressingly large gap in weathering’s reaction velocity relative to scientists’ career velocity.

***

"One way was to find rock that weathers fast. The Rio Blanco Quartz Diorite bedrock beneath the Rio Icacos watershed in Puerto Rico weathers exceptionally fast, making it a tempting target for an experiment conducted on a publishable timescale. The scientists took samples of pure bedrock from a roadcut as well as long tubes of soil and rock drilled into the formation from above. Included in these cores was the transition zone where fractured bedrock alternates with veins of newborn soil, a region is somewhat oddly called the “rindlet” zone (which sadly does not yield anything crunchy and delicious sold in 99-cent bags).

***

"All living beings juggle electrons, usually by stripping them from sugars and other reduced organic compounds (stuff we call “food”) and using those electrons to power their cells through cellular respiration. But some microbes can use simple inorganic compounds or atoms as electron sources. The ones that can use stone as a source of electrons are called lithotrophs. They eat rocks.

"Minerals rich in reduced iron like pyrite (fool’s gold), biotite, and hornblende are potential bacteria chow. The physical changes to these minerals wrought by electron stripping should initiate the process of their chemical dissolution — that is, weathering. This should be visible under the microscope as some sort of physical alteration.

"So the scientists took their highly weather-able rock and microbe-laced soil back home and accelerated the proceedings further by grinding the rock, increasing its surface area. They mixed crushed rock with microbes.

***

"After 30 months, they put their samples under the microscope. The minerals incubated with microbes appeared ragged or pitted — as if they had been dipped in acid, not bacteria — after their 864-day incubation. The sterile control minerals, by contrast, retained sharp, smooth edges.

***

"The lithotrophic bacteria they did find have a special power: the ability to harvest electrons from iron atoms outside their bodies. That is, they can eat without swallowing their food. The bacteria “ingest” the electrons in a technique called external electron transfer. This is vital because the iron atoms are part of the mineral and the bacteria have no crow bars or other means with which to pry them loose. But there is another advantage to doing it this way: if the iron atoms were ingested before oxidation, the microbes would fill with rust, a potentially lethal and definitely embarrassing situation.

"So, bacteria indeed appear able to initiate and accelerate the dirt-making process. On land, dirt supports plants, which support most everything else. In this way among many others, life feeds back, yielding the planet we see today in which no surface remains uncolonized, and the height and depth at which life vanishes remain unknown."

Comment: I've described the Earth as being evolved by God's creations in life. Starting with bacteria as God's workhorses, our Earth beautifully supports all sorts of life in a vast necessary bush of life. Analyzed this way God's methods for His purposes are easy to understand.


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