Dropping drills up to 19,000 feet deep some 1,400 miles northeast of New Zealand, D’Hondt and his colleagues were on a mission to probe these ancient deep-sea sediments for life. Much of the seafloor could be volcanic ash blown from the land, as well as metallic bits from space. “There’s a measurable fraction of it that’s cosmic debris,” says D’Hondt. “If you trawl through the shallow clay with a magnet, you’ll pull out micrometeorites.”
Even at the surface of the sediment, where sea cucumbers roam, you’d expect to find very few microbes—relatively speaking. “At the seafloor there, you might have a million microbes per cubic centimeter,” says D’Hondt. “Whereas off of San Francisco, you might have a billion or 10 billion per cubic centimeter.” The researchers expected, then, to find fewer microbes even deeper, where organic matter is essentially nonexistent.
To capture those microbes, they drilled down through 75 meters of superfine sediment until they hit that basement of volcanic rock, then collected their samples. From previous drilling nearby, they knew they’d be grabbing 101.5-million-year-old muck—sedimentation gathers in this part of the sea at a rate of perhaps 10 centimeters every million years.
Sediment samples in hand, Yuki Morono—a geomicrobiologist at the Japan Agency for Marine-Earth Science and Technology (known as JAMSTEC) and lead author of the new paper—now had to search through the ultra-fine sediment for ultra-tiny microbes. In principle, the process should have been straightforward. Morono used a chemical that stains DNA, ferreting the microbes out of their hiding places amid multitudinous other sedimentary particles.
What he found was astonishing: 1011 cells per cubic centimeter of sediment that should, in theory, be scant in terms of life. JAMSTEC’s directors were ecstatic. “They were saying that they were groundbreaking results and will rewrite the textbooks or something. And I was so worried about that,” recalls Morono. Such a high cell count in sediment almost devoid of nutrients and oxygen rang alarm bells for him. So Morono picked apart his own techniques and results and found that something was indeed awry. “Finally, within something like a half a year or so, I could prove that the results were wrong: More than 99 percent of the cells I detected by the previous technology were not cells,” he says.
A paper he had submitted to a journal was actually in peer review at the time and had to be pulled. But he decided to try again. “Based on that very bad nightmare memory, I tried to develop the technology to be sure,” Morono says.