16 Non-Human Alchemists II: Bacteria
Human bodies are colonized by many billions of microorganisms: in the hair, throat, stomach, genitals, skin, and elsewhere. Some estimates state there are three non-human cells on and in our bodies for every human one: ancient invaders that pre-date the arrival of homo sapiens by millions of years yet make our energy, health, and bodily regulation possible, particularly those involved with breaking down food and absorbing its nutrition in the mouth and gut. The Human Microbiome Project, which published its first results in 2012, found that humans host thousands of bacteria, most of all in the mouth and small intestine, which boasted the greatest diversity.
Just as bacteria play an essential role in bodily function, they are among the most integral “non-human alchemists” at work at planetary scale. Bacteria can be sensitive to heat and light, but they can also be among the most extreme organisms we know of, flourishing in space, in radioactive waste and deep under ground. Deep subsurface bacteria accounts for 13 percent of the planet’s biomass. Microbial metabolic functioning drives the biogeochemical transpositions that define earth ecosystem dynamics as matter cycles between the lithosphere, atmosphere, hydrosphere, and biosphere.
Consider nitrogen: the most abundant element in the atmosphere that plays some role in all life on the planet. Bacterial microorganisms, for example, facilitate the symbiotic exchange of nitrogen and carbon compounds between rhizomes and legumes, and are essential in the interconversion between organic and inorganic forms of nitrogen as it cycles between the atmosphere and terrestrial and marine ecosystems. Scientists at Gingko Bioworks and Bayer joint venture Joyn Bio are using synthetic biology to modify soil microbes so they can synthesise nitrogen directly from the atmosphere – boosting yields while reducing the need for fertilizers.