Lack of Molybdenum May Have Delayed Life on Earth

esocid writes "Scientists from around the world have reconstructed changes in Earth's ancient ocean chemistry during a broad sweep of geological time, from about 2.5 to 0.5 billion years ago. They have discovered that a deficiency of oxygen and the heavy metal molybdenum in the ancient deep ocean may have delayed the evolution of animal life on Earth for nearly 2 billion years. Bacteria cannot fix nitrogen efficiently when they are deprived of molybdenum. And if bacteria can't fix nitrogen fast enough, then eukaryotes — a kind of organism that includes plants, pachyderms and people — are in trouble because eukaryotes cannot fix nitrogen themselves at all. Ariel Anbar, a co-author of the research of Arizona State University, stated that "eukaryotes depend on bacteria having an easy enough time fixing nitrogen that there's enough to go around. So if bacteria were struggling to get enough molybdenum, there probably wouldn't have been enough fixed nitrogen for eukaryotes to flourish.""

terraforming and other things

This casts an interesting light on the idea of terraforming. There's often been the idea that we could just introduce plants into a CO2 rich environment and in pretty short order we'd have a breathable atmosphere. Apparently that may not be the case. Without an oxygen rich environment to free the molybdenum, there's no significant nitrogen fixation and thus those plants are going to be hurting pretty quickly.

Also, this makes me wonder what those eukaryotes were doing for the first 2 billion years. Were they undergoing all sorts of genetic mutations that primed them for takeover once the situation changed? IOW, I wonder what would have happened if this little molybdenum problem had resolved earlier. Would the eukaryotes continued to flounder (pun!) because of a lack of genetic diversity? Or would they have just as rapidly developed putting the current day well into the cockroaches-rule-the-earth epoch?

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For what its worth, I don't think there's often that idea among plant biologists.

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I'm sure you're right. I'm speaking more about my more-or-less common man image of terraforming... at some point natural processes take over and the whole "just works". But the need for free molybdenum to support nitrogen fixing sort of throws a monkey-wre

Re:terraforming and other things

Well, I'm no biologist but right off the cuff I think there are some problems with this "theory"... it makes an assumption that in an environment without fixed nitrogen that complex life would not have evolved to either not need it or to do it itself. It also assumes that the availability of molybdenum is required to fix nitrogen.

The fact that eukareotes did not evolve it doesn't mean they couldn't have -- it just means that their environment they evolved in didn't need that ability, likely because prokaryotes evolved it already. (Or they didn't actually originally need it -- which may make more sense because if one assumes that that evolution was necessary for eukaryotes, and they evolved from prokaryotes, then how did they *lose* that ability?)

Again, not a biologist but the critical reader in me gets a "I have a hammer, so everything is a nail" vibe from this theory.

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Well, I'm no biologist but right off the cuff I think there are some problems with this "theory"... it makes an assumption that in an environment without fixed nitrogen that complex life would not have evolved to either not need it or to do it itself. It also assumes that the availability of molybdenum is required to fix nitrogen.

I'm no biologist either... all the more reason for us to get really nasty and get a right proper flamefest going!! ;-P

So, there are certain rules to the chemistry that underly biology and (really really speculating here... in fact this whole thing is just

Re:terraforming and other things

Nitrogen is part of both DNA and amino acids. Therefore all life as we know it requires it. We can speculate about other types of lifeforms that doesn't use DNA, but as far as we know the, nitrogenases are the only enzymes that takes nitrogen gas to a usable form (ammonia).

It is important to realize that life on earth didn't all come to existence at once. Animals cannot breath CO2 not because it can't evolve for it but because our metabolism depends on oxygen. Without plants fixing CO2 and putting out O2, *for millions of years*, animals couldn't exist. Plants couldn't evolve to fix nitrogen in the similar way. Read up on the nitrogen cycle.

BTW, IMAB (I am a biologist).

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> Read up on the nitrogen cycle.

I did. and molybdenum was not mentioned anywhere.

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Sigh. [google.com] How hard did you look, exactly?

(Mo is used as a cofactor, meaning that it can be used over and over again without being depleted. You just need a single atom of Mo per enzyme.)

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Nope. You lose. Bacteria/Prokaryotes/lots of protolife evolved first. I don't have a Biology textbook in front of me, but here [wmnh.com] is an online reference. IAAB (student)

Re:terraforming and other things

But what is the advantage to learning how to fix nitrogen if there is already sufficient amounts around?

It's all about evolution. Sure, you* have enough NH3 to survive, even to grow, but there's millions of tons of N2 gas in the atmosphere, and if you could somehow use that as a fuel source, you'd be set for life.

So then, along comes a random mutation in an enzyme that pulls converts nitrites to nitrates (I'm making this up - but it was probably some enzyme to do with N). Rather than killing you, it allows you to pull N2 out of the air and turn it into ammonia, allowing you to reproduce more quickly. Now another mutation comes along, and it allows you to use Mo to push forward the reaction (mind you it worked before you had Mo: reactions can generally go forward without their cofactors, just more slowly.)

With this cofactor, you're able to reproduce much more quickly than your neighbors which don't have the mutation, and you become the bacteria we know today.

*you here refers to a now-extinct progenitor of nitrogen fixing bacteria. Individuals reproduce, populations evolve.

So maybe it was mostly nitrogen fixers around, but they weren't doing very well because of a lack of molybdenum?

Like I said, cofactors generally speed up a process. They are not generally required for the reaction to happen, they just speed it up (by several orders of magnitude) when they are present.

42

Its the ultimate answer to life and everything.

According to wikipedia.

Molybdenum is the 42nd-most-abundant element in the universe

Coincidence? I think not!

Re:42

Its the ultimate answer to life and everything.

According to wikipedia.

        Molybdenum is the 42nd-most-abundant element in the universe

And it can hardly be coincidence that you fail to mention its atomic number is also 42!

ZOMG! Is it April Fools' yet?

--
Toro

Re:42

Holy crap! There are 42 protons in its nucleus!

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Holy crap! There are 42 protons in its nucleus!

You dope. That is what the atomic number means.

It was all being saved

to build Crow T. Robot.

the deity screws up again

Bacteria cannot fix nitrogen efficiently when they are deprived of molybdenum So when God created the earth, all of his nitrogen was broken?

Molybdenum?!

Damn near killed 'um!!

*ducks*

Author needs to study some biochemistry

It's so sad when bad things happen to good ideas. The fact that there may have been dearth of molybdenum in the early oceans isn't a crippling blow to the development of eukaryotes.

Nitrogenase, the enzyme that performs nitrogen fixation today, commonly uses, but doesn't require, molybdenum for its function. There are forms of the enzyme that use vanadium or iron as a cofactor to the ubiquitous iron-sulfur cluster that actually performs the chemistry.

I don't know if this event happened before or after the iron catastrophe, but the fact that the enzyme uses iron anyway makes me believe that there must have been enough iron around the oceans back then. Methinks the author's running off the old idea that the nitrogen reduction occurs on the molybdenum atom instead of one of the iron atoms in the iron-sulfur cluster.

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Oddly enough, none of the articles on nitrogen fixation even mention moly....
Whats that all about?

Re:Excitement

Not necessarily. The use of bitumen/tar was documented in biblical times [ourfatherlutheran.net]. The Romans were thought to have used coal for metalwork [wiganarchsoc.co.uk]. A Greek by the name of Heronas, developed a prototype steam engine. [e-telescope.gr] They might have advanced faster technologically, if they weren't afraid of making the slaves unemployed [mlahanas.de]

You can also read the history of the combustion engine [about.com]. The first combustion engines were based on gunpowder, then coal powered steam engines, coal gas, and finally petroleum. At the same time, engineers experimented with one stroke, two stroke and four stroke engines with vertical and V slant pistons.

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It's the 1910s. Where do you get a high-energy-density fuel that's readily available? Certainly not from corn; chemistry was just accepting the Rutherford model, they're not exactly modern chemists.

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it was my understanding that henry ford opted to use petroleum over a 'design that would have used peanut oil' much like our modern diesel engines... while it may be true that the model t could run on corn fuel, remember that at that time they could easily

Re:Excitement

The Romans were thought to have used coal for metalwork

I didn't know that there was any other way besides coal/coke for the ancients to have done blacksmithing, although wikipedia says it can be done with charcoal. I have no idea how charcoal would work. The Wikipedia article isn't quite accurate:

Blacksmiths work by heating pieces of wrought iron or steel in a forge until the metal becomes soft enough to be shaped with hand tools, such as a hammer and chisel. Heating is accomplished by the use of a forge fueled by propane, natural gas, coal, charcoal, or coke.

You can't blacksmith using just coal; the coal is turned to coke [wikipedia.org] by oxygenating it with a blower, and pouring water on it. At least that's what they taught in my college blacksmithing class. I can't remember the fellow's name, unfortunately, but he was 72 at the time and travelled to different universities teaching his dying art to the younger generation. This was some time in the late 1970s. He'd smithed Gerald Ford's wrought iron fence, at the time of the class Carter was president.

I really should build a forge.

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Larry Niven's World of Ptaavs, now one of his most forgotten novels but important as his first Known Space book, had the Earth being a "food planet" of galactic empire several billion years ago. Humanity ended up evolving out of the ooze that was being gro

Re:Interesting thought for a sci-fi novel

That reminds me of a quote from Chuck Palahniuk:

"Centuries ago, sailors on long voyages used to leave a pair of pigs on every deserted island. Or they'd leave a pair of goats. Either way, on any future visit, the island would be a source of meat. These islands, they were pristine. These were home to breeds of birds with no natural predators. Breeds of birds that lived nowhere else on earth. The plants there, without enemies they evolved without thorns or poisons. Without predators and enemies, these islands, they were paradise. The sailors, the next time they visited these islands, the only things still there would be herds of goats or pigs. .... Does this remind you of anything? Maybe the ol' Adam and Eve story? .... You ever wonder when God's coming back with a lot of barbecue sauce?"