Their strategy for staying alive is to be barely alive at all. Their metabolism is dialed down to almost nothing, an adaptive advantage in a place with so few resources. The bacteria that survive are the ones that can satisfy themselves with minute traces of oxygen and a parsimonious diet of organic material laid down millions of years ago.
Such buried bacteria have been found before, but a new study, published Thursday online by the journal Science, has provided the clearest look at their glacial pace of existence. The conclusion, in short, is that microbes can putter along at extremely low rates of oxygen respiration, their numbers limited only by the paucity of energy available in the buried sediment.
“These organisms live so slowly that when we look at it at our own time scale, it’s like suspended animation,” said Danish scientist Hans Roy, a biologist at Aarhus University and the lead author of the study. “The main lesson here is that we need to stop looking at life at our own time scale.”
An ancillary message is that human beings should not be too chauvinistic about what constitutes, or characterizes, a living thing.
There are a lot more nuances to nature than scientists realized just a few decades ago.
The ingenuity of life gives hope to researchers looking for evidence of life beyond Earth. Extraterrestrial life could conceivably be detected by robotic probes, for example, in the Martian subsurface, or in an ice-
covered ocean on a cold moon farther out in the solar system.
‘Life in the slow lane’
Scientists now believe that much of the life on Earth is barely able to fog a mirror, as it were. The deep-sea microbes may be an extreme example of a laid-back norm.
Most of Earth life, measured by numbers, is not rambunctious and charismatic like life in the sunshine, nor is it akin to the microbes that grow quickly in a laboratory petri dish.
Rather, it’s kind of boring — living out of sight, below the surface, in total darkness, using energy slowly and efficiently.
NASA research scientist Tori Hoehler, who was not involved with the new study but who has investigated such microbes, said, “I think this is a window into life in the slow lane, which, far from being a niche thing, is probably the average condition on Earth.”
Only in recent decades have scientists come to realize that life on the surface is but the flashy veneer of the biosphere.
Life, we now know, will find a way to survive in the unlikeliest places, from deep-sea hydrothermal vents and ancient salt deposits to Yellowstone’s hot springs. There are microbes living on aerosolized particles high in the atmosphere.
But the subsea, buried bacteria demonstrate a form of extremophiles that are at the end of the spectrum of vibrancy.