Researchers assume that most of the novel DNA is microbial in origin, but they have yet to identify the organisms or see what they can do, because most microbes are notoriously difficult to cultivate in the lab. Bacteria may happily swim through toxic waste, but when it comes to confinement on an agar plate, thank you, they’d rather be dead.

Technical challenges notwithstanding, scientists have made some progress in investigating preposterous life forms and tallying the biochemical tools that such extremophiles use. Thermophilic microbes, for example, which can withstand temperatures of 238 degrees Fahrenheit, well above the boiling point of water, have stiffening agents in their membranes, to keep them from melting away, and they build their cell proteins with a different assortment of amino acids than our cells do, allowing the construction of strongly bonded protein chains that won’t collapse in the heat.

By contrast, said Steven K. Schmidt, a microbiologist at the University of Colorado in Boulder, when you look at organisms that thrive in subzero conditions, “their membranes are really loosey-goosey, very fluid,” and so resist stiffening and freezing. It turns out there are a lot of these loosey-gooses around. Dr. Schmidt and his colleagues study the fridgophile life forms that make their home in glacial debris high in the Andes Mountains, 20,000 feet above sea level, where the scene may look bleak, beyond posthumous, but where, he said, “we’ve been pretty amazed at the extreme diversity of things we’ve found.” The complexity of the Andean microbial ecosystem, he said, “is greater than what you’d find in your garden.”

Yes, microbes were here first, and they’ve done everything first, and synthetic lifers are happy to scavenge for parts and ideas. Drew Endy, an assistant professor in the biological engineering department at the Massachusetts Institute of Technology, and his colleagues are putting together a registry of standardized biological parts, which they call BioBrick parts. The registry consists of the DNA code for different biological modules, interchangeable protein parts that they hope may someday be pieced together into a wide variety of biological devices to perform any task a bioengineer may have in mind, rather like the way nuts, bolts, gears, pulleys, circuits and the like are assembled into the machines of our civilization. Numbering some 2,000 parts and growing, the registry contains many recipes for clever protein modules invented by bacteria. One sequence engineered by researchers in Melbourne, Australia, encodes the instructions for a little protein balloon, for example. “It’s based on a natural part found in a marine micro-organism that controls the buoyancy of the cell,” Dr. Endy said.

Invisible though it may be, the microbial community ever keeps us afloat.