For starters, if we are to believe that our elders deserve respect, cyanobacteria certainly qualify. They date back 3.5 billion years, almost to the earliest signs of life. But they are not only old. They are interesting, they seem uncomplicated, and they are powerful and successful. They are single-celled, though many live connected to each other in colonies and filaments. They are primitive; unlike the cells of younger species, they have no nucleus. And they have not only survived all this time; they have thrived. Their species number at least two thousand that have been described and at least twice that number in total. Most are blue-green—“cyan”—but their various pigments also account for the colors of pink flamingoes and the Red Sea.
Cyanobacteria gave us oxygen—and continue to do so. For the first two billion years after the earth’s formation 4.5 billion years ago, the atmosphere contained almost no oxygen. But the blue-green pigment in cyanobacteria is a mix of green chlorophyll and a blue pigment both of which turn sunlight and carbon dioxide into sugary energy for the cell. Oxygen is the waste product—and early cyanobacteria produced so much of it for so long that it accumulated in the atmosphere and eventually supported larger, more complex cells, including ours.
Just as important, atmospheric oxygen spawned an ozone layer that reduced the lethal levels of the sun’s ultraviolet radiation. It’s that filtering that allowed early plant and animal life to finally move on to land after three billion years in the water.
Cyanobacteria made plants themselves possible by becoming part of them. Some other early bacteria engulfed cyanobacteria and then, because of cyanobacteria’s efficient energy production, turned them into one of the pieces of organic machinery enclosed within a plant’s cell. We see them today as the greenery of plants—the chloroplasts—that power them and keep them reaching for the sun.
Cyanobacteria are handy with another gas in addition to oxygen. They convert nitrogen in the atmosphere into a form that plants and animals need for such building blocks as proteins and DNA. Natural nitrogen fertilizer.
As for that one nasty trait, cyanobacteria can kill you. Especially in freshwater ponds and lakes, blooms of cyanobacteria looking like blue-green paint slicks may be toxic to nerve and liver systems, depending on the species. The poisons may work their way into the food chain, pets may eat them, water-skiers may absorb them. The result can be respiratory failure, Parkinson’s, ALS. Not often, but too often. Respect.Cyanobacteria often go by the name of blue-green algae. But they’re not algae. Algae is an informal term for many water-borne organisms that contain chlorophyll but lack stems, roots, or leaves. Seaweed is algae. Cyanobacteria are bacteria—simple cells, often strung together, without nuclei.
Reading about cyanobacteria on the Internet, you get a glimpse of a life-form from an inconceivably ancient world that is woven throughout the air, water, and soil of our own time. We are in their debt for the breath we take, the food we eat, for our living on solid ground. We stand on their countless, tiny shoulders.
This article first appeared at 3.8 Billion Years.
I grew up in New York City and now live in New Jersey, where I taught English for four decades at a community college, a profession I found varied and rewarding. I’m married, with family in the area.
I retired in 2006 in part to fight poverty as best I could, at every level I could–locally, nationally, and in Africa. I’ve become a local volunteer and on-line advocate and along the way have learned fast about the economic, political, and legal issues that accompany poverty.
I also found myself thinking more about the central questions that catch up with us sooner or later: What is my purpose? How will I face death? What do I believe in? I have always liked the descriptions from science about how living things work, about the history of the earth, about the nature of the cosmos. But I could not put those pictures together with my questions. Gradually I came to see that life’s history over 3.8 billion years stood inside and throughout my being and constituted my livingness at its core. In my blog at threepointeightbillionyears.com, I’ve been exploring the variety of ways in which our experience is anchored not just in our evolution from primates but in the much longer lifespan of life itself.
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