Scientific American reports on new evidence that bacteria may be “effectively immortal” after researchers brought back microbes that settled to the ocean floor tens of millions of years before the dinosaurs went extinct:
The sea here is so miserly that it takes one million years for a meter of marine “snow”—corpses, poo and dust—to accumulate on the bottom. The tale of all that time can total as little as 10 centimeters. It is the least productive patch of water on the planet.
Through nearly 6,000 meters of this seawater the IODP team lowered a drill. The strawlike bit plunged into pelagic clay and calcareous nanofossil ooze at three sites on the bottom.
By the time the cores of sediment were raised to the surface, the tubes contained up to 100 million years of Earth history. What the team wanted to know was how long and in what state microbes trapped in this milieu could survive in an almost-completely raided oceanic refrigerator. They were in for a surprise.
Their results, published in Nature Communications in July, revealed that the sediments contained bacterial cells, which they expected (not many, though: just 100 to 3,000 per cubic centimeter). But when given food, most of them quickly revived, which the scientists did not expect.
The microbes got straight to work doing what bacteria do, and within 68 days of incubation had increased their numbers up to 10,000-fold. They doubled about every five days (E. coli bacteria in the lab double in around 20 minutes). Their progeny contained specially labeled isotopes of carbon and nitrogen that made the scientists sure that the microbes were eating what they had been offered.
It’s worth pausing to consider the meaning of these results. In this experiment, cells awoke and multiplied that settled to the bottom when pterosaurs and plesiosaurs drifted overhead. Four geologic periods had ground by, but these microbes, protected from radiation and cosmic rays by a thick coat of ocean and sediment, quietly persisted. And now, when offered a bite, they awoke and carried on as if nothing unusual had happened.
You can read the Nature Communications study here.