The Moss After Tomorrow

Last weekend I found myself in the black forest, in the south west corner of Germany. I spent much of Saturday afternoon wandering through the woods surrounding a beautiful lake named ‘Titisee’.

There was so much to see here that choosing something to focus on for this month’s blog entry was nigh on impossible, the grand old pine trees,

the creepy stump fungus…

The tacky tourist shops,

But none of them were exciting enough, they lacked pizazz, they lacked charm. No, what I needed was a muse to set the pulse racing, what I needed…. was moss.

If you need to take a moment to calm yourself before reading on, I completely understand. You might try watching this, or this, or maybe for the more adventurous, this.1

Moss is frequently overshadowed by it’s larger and more boisterous cousin, the tree. But after a couple of beers, it likes to spin a yarn where as a younger genus, on a dare from some cyanobacteria, it sent earth into a million year long ice age.

If you haven’t had the pleasure of spending an hour or two with some moss down at your local, I’ll tell the story later. But first… some science. Mosses don’t take up nutrients from the soil like grasses or bushes, instead they get their nutrients from the air and the surface of the ground.

You might not think that the surface of a rock would have much nutritional value, but there is actually a whole stack of biologically useful stuff locked up in rocks. Most living things don’t bother trying to access them, but moss is no ordinary organism.

Some mosses can secrete ‘organic acids’ that are able to dissolve rock. The nutrients in the dissolved rock can then be taken up by the moss to help it grow. Sadly, I don’t have space here to talk about all the organic acids that mosses can make, so I’m just going to discuss the one, malic acid. Below is my attempt to show one of the ways that mosses can make this compound.

Download (PDF, 607KB)

The compound at the top of this month’s biosynthesis doesn’t have anything added to it in the first step. You might notice that Greg does remove two hydrogens (the green circles), but this isn’t the most obvious change. The two carbons in the middle of the compound are simply connected differently.

On the face of it, that looks like a completely pointless exercise. Two bricks side to side are no closer to making a house than two bricks one on top of the other.2 If you only have two tires, it doesn’t matter which wheels you arrange them on, you’re no closer to having a functioning helicopter destroyer. If you have ten thousand spoons, none of the ways that you can arrange them will have you any closer to holding a knife.

But the new arrangement of our compound is just a little bit special. Imagine a high jumper preparing to clear a bar. She needs to crouch slightly on her last step to give her the energy to get over that bar. That second arrangement of carbons is a bit like the crouch position, an energetically more explosive arrangement that can help the compound do difficult things. And it’s this new energy richness that allows Phil to take the compound and react it with some water. The building blocks of water get split between those two middle carbons to give malic acid.

An academic group out of the UK, argue that the secretion of organic acids by an ancient ancestor of moss, might have helped to cause an ice age around 445 million years ago.

Moss is a part of a family of plants called bryophytes, who were the first plants to establish themselves on dry land around 460 million years ago. The theory goes, that when these plants started growing over rocks and dissolving their nutrients for the first time, the surplus nutrients washed into the oceans and made a feast for algae. The amount of algae around boomed, sucking carbon dioxide out of the atmosphere to a point where the planet cooled and entered a million year long ice age.

As a theory, it’s all well and good. But it’s got to be the least cinematic cataclysm imaginable.

No-one is paying money to watch Will Smith wander the planet burning moss wherever he finds it to stop the coming Armageddon.

Although, if you’re reading this Mr Smith, I have a wicked idea for a musical based on the Krebs cycle – call me.


1: If you’ve never spent an hour of your life listening to someone delicately flick the bristles of a hairbrush, you’ve made better life choices me.

2: Source required