When Mt. St. Helens erupted in Washington State, the surrounding ecosystem was pulverized into a barren land of sterilized ashes. Plants couldn’t grow there, and without them, animals were absent.
But eventually, slowly and surely, life returned. How did this happen? It could only occur after the arrival of invisible life.
Microbes were the pioneering species that chemically converted the nutrient-poor soil into something livable again. These microbes broke the ash into a home for lichens (an algal-fungal complex) and a few weedy plants. This paved the way for recolonization on a higher level.
Microbes – which is a catch-all phrase for bacteria, archaea, protozoans, algae, microscopic fungi, and other microscopic eukaryotes – make up the foundations of ecosystems worldwide. Without them, life as we know it would not exist. There are more bacteria on earth than there are stars in the universe. What’s more, these bacteria work closely not only with ecosystems, but with individuals – including you. By cell count, you are only 10\% human. By gene count, you’re only 1 or even 0.1\% human. In fact, you share more genetic material with any other person on the planet than you do your gut microbes. (Any two people have the same 99.99\% of their DNA; any two people share only 10\% of their internal microbial inhabitants.)
What are all these microbes doing? Saving the world, apparently – and humanity in the process. Children exposed to good bacteria at an early age are more likely to have properly developed immune systems. Since we’re exposed to good bacteria on a daily basis, our immune system requires exposure to bacteria at a young age in order to properly “calibrate” the system. In a sterile environment, your immune system won’t develop properly, and allergies, asthma, and autoimmune disorders may be the result.
Another unseen hero of life is the virus. These things are simply packets of genetic material coated under a protein envelope; their only way of reproducing is by exploiting the DNA replication proteins of a living cell. While we know them on a pathogenic level, it turns out that viruses in the ocean inject DNA into cyanobacteria whose DNA has been damaged from constant UV exposure. Without the virus, cyanobacteria would die from DNA loss. Since cyanobacteria and other marine phytoplanktons conduct around 50\% of the world’s photosynthesis, these viruses literally keep earth’s inhabitants breathing.
Bacteria have also been observed eating oils and plastics, and removing heavy metals from the environment – in both land and sea.
The other half of photosynthesis is conducted by forests and they, too, depend on hidden helpers. While these fungi aren’t exactly microscopic, they are mostly unseen by us.
What is a fungus? In plants, we are most familiar with the main body of the plant – twigs, leaves, flowers, tree trunks – and only the roots dwell underground. But in fungi, the mushroom caps we are accustomed to seeing are just a small sliver of the story. Mushrooms are just the reproductive parts of the fungus, kind of like plants’ fleeting flowers. The main body of the fungus is actually its “roots,” which are called mycelia. These mycelia are the hidden life blood of the forest.
When you walk into a forest, you are walking into a very complex web. No, literally – it is a web, with each constituent woven into the others. Underground, every single plant is connected to every other. Trees and shrubs, oaks and blackberries, trees of different ages, plants of different species, are connected together. Nutrients are distributed to where they are most needed, and taken from where they are not needed. All this is done by mycelia, which weave the roots of the whole forest together. The mycelia even allow parent trees to nurture their seedlings around them.
But that’s not the only thing fungi do. A second role of the Fungus Kingdom was discovered as a result of some very needed research in forestry.
After a certain parcel of land is cleared for lumber, it is customary to burn it down, and then (to ensure sustainability) replant young seedlings in the fresh land. They’ll import seedlings of native trees grown in nurseries, plant them, and check on them every few years to see how they’re doing. After a couple check-ups, however, scientists, without fail, saw a total and complete mortality rate among the seedlings.
The first guess for the cause of this tree genocide was gophers. After extermination didn’t improve mortality rates at all, they guessed that the other shrubs and herbs that had sprouted up there were outcompeting the seedlings. But when weeding the parcel didn’t help either, further research was obviously required to ensure sustainability (and save money on seedling planting and care in the future!)
The scientists eventually discovered that fungi help trees grow. And not only that, fungi are necessary for tree survival. Comparing nursery-grown seedlings to wild-grown seedlings of the same age was a clue: the wild-grown seedlings were noticeably larger and healthier than the nursery-grown ones. This turned out to be because in wild seedlings, fungi in the surrounding soil would settle into the young plants’ roots and increase their water absorption rate so that the seedlings could grow in size. Nursery-grown seedlings had been raised in sterile soils, and after planting them in fungus-starved, fire-scorched land parcels, they didn’t stand a chance. The scientists were able to fix this seedling mortality by simply taking surrounding soils and sprinkling it throughout the land parcel, inoculating the soils with fungus spores and other healthy forest microbes. They were rewarded with seeing the next set of seedlings happily and hardily take root.
Fungi, bacteria and viruses are unlikely heroes of the natural world. They boost health, boost productivity, and permit life to take hold in what would otherwise be a very barren earth.
The Gut Check, a MOOC at Coursera
My botany professor : )
Lectures by Dr. Todd Charles Wood and Dr. Joe Francis (See my essay, “The Fall, the Flood, and Creation Biology”)
Prescott’s Microbiology by Willey & Sherwood
Raven Biology of Plants by Evert & Eichhorn