Some Non-Human Arsenic Eaters
We start this chapter with a seemingly unlikely question: Is arsenic essential for life on Earth? This idea was given some traction when NASA researchers thought that they had isolated a microorganism that had substituted arsenic for phosphorus in DNA, the blueprint of an organism. This news received considerable media attention as well as skeptical responses from the scientific community and was eventually debunked. But, as we shall see, arsenic is involved in some other life processes, some of which probably developed as the Earth was being formed. For one microorganism, arsenic is essential for life. All organisms are exposed to arsenic—because it is everywhere—and therefore take it up from the environment. Most organisms, including humans, have developed ways to transform one arsenic compound into another, and this has given rise to a wide range of different arsenic compounds, which are found in plants and animals and therefore in our food. It is not the pure element arsenic that we are exposed to but a variety of inorganic and organic arsenic compounds, each with its own unique properties.