October 30, 2010
We live in a world of small things, but did you know that a world of small things also lives in us? According to an article in Miller-McCune magazine titled, Bacteria “R” Us, http://www.miller-mccune.com/science-environment/bacteria-r-us-23628/, an estimated ninety percent of the cells in the human body are not human cells at all. They are bacteria. If you add in the cells of yeast and other fungi living on our skin and mucous membranes, estimates run even higher.
While we may find this a little creepy, the article goes on to point out that, “In fact, most of the life on the planet is probably composed of bacteria. They have been found making a living in Cretaceous-era sediments below the bottom of the ocean and in ice-covered Antarctic lakes, inside volcanoes, miles high in the atmosphere, teeming in the oceans — and within every other life-form on Earth.”
Bacteria reproduce by cloning and can double their numbers every 20 minutes. They maintain genetic diversity by “conjugation”, the transfer of genes between bacteria in close proximity to one another. They form communities called biofilms, exhibit group behavior such as swarming and communicate with each other and their hosts’ cells through chemical “language”.
Bacteria can be either pathogenic or beneficial. Sometimes, they can be both. For example, E coli, which we have heard so much about in the news lately, lives in our gut where it fends off pathogenic bacteria, helps break down food so that its nutrients are released in a form our bodies can use and makes vitamin K – which our bodies use in blood clotting and to help build healthy bones. Most bacteria in our guts are engaged in similar helpful pursuits. Researchers are finding that whether a bacteria turns pathogenic often depends on conditions in our own bodies. Poor nutrition, surgery, stress and other things that affect our immune system and alter our body’s normal metabolism, can alter the nutrient supply for the bacteria living within us, which can trigger them to release toxins or attack the cells of our gut where they usually co-exist peacefully with us.
While the article pertained to bacteria, our bodies are also inhabited by fungi, mainly in the form of yeasts and, perhaps, mold spores. Although there are far fewer fungi than bacteria in or on our bodies, they may also contribute to human health by generating growth factors and vitamins from what we eat and by out-competing some harmful bacteria and fungi for food supplies and by their natural antibiotic production.
Outside our bodies, an equally give-and-take world exists between humans and these small things which benefits us. The world would be a strange and, probably, unlivable place if nothing ever decomposed after it died. However, both bacteria and fungi are prodigious decomposers of organic matter, returning its constituent molecules to the soil for reuse by plants and the animals, including us, who depend on those plants for nutrition. We use both bacteria and fungi to ferment foods, make wines, beers, cheeses and yogurts. We use cultures of yeast – a fungi – to make bread. We eat mushrooms and truffles, which are the fruiting bodies of various fungi. Both fungi and bacteria produce antibiotics; fungi also produce anti-fungals against other fungi that cause infections; and we use statins made by fungi to control our cholesterol production when it’s high.
As every gardener worth his or her salt knows, at least intuitively, a garden is a world where plant roots engage in a delicate dance with a multitude of microscopic organisms such as bacteria and fungi. Within the rhizosphere – that ecologically active area immediately surrounding a plant’s roots – plant roots provide bacteria and fungi with carbon while, in breaking down and decomposing organic matter, fungi and bacteria provide the plant roots with nitrogen and minerals the plant needs while increasing soil fertility and making water more available.
The dance, of course, is much more complex than that, as is our own. But, the article and others I subsequently read this week reminded me that we “higher” forms of life on the planet are embedded in a vast, often unnoticed and mostly unappreciated web of life that depend on fungi and bacteria – and the other small things of this world – for survival. For a couple of billion years before we came along, they were busy changing the environment to a form in which we could exist. And I suspect that even if we manage to destroy ourselves, they will go on undoing our damage and restructuring the planet for other, perhaps newly evolving life forms we don’t yet know of.
So next time you’re up for a beer or a glass of wine and some cheese, hoist one in toast to the small things that made it and, probably, us possible.
If you’re interested in reading more, here are links to some other articles I read this week about small things: