Scientists are interested in extremes. The biggest and smallest, slowest and fastest tend to tell us more about the ultimate rules and limitations that govern all of life than the middle-of-the-road. During a recent trip with the research vessel R/V Knorr, scientists found something remarkable. Drilling sediment cores from the bottom of the North Pacific Gyre, a huge system of currents between North America and Asia, they found bacteria living life as slowly as possible.
Normally, oxygen penetrates only a few centimeters or decimeters down into the seabed. These bacteria, however, were living off oxygen more than twenty meters below the seafloor. There’s very little of either oxygen or organic material for the bacteria to live off, so in order to survive, they must live so slowly that they’re barely alive at all. The researchers measured carbon oxidation and assumed that this corresponds to the bacteria’s oxygen comsumption. By counting the number of cells and measuring the oxygen concentration, they could calculate roughly how slowly the bacteria metabolize. This tapered off at 10-3 femtomoles per cell per day, which equals only seven oxygen molecules per second. That is unbelievably slow. The results were consistent over many core samples from varying conditions, suggesting to the researchers that “these microbial communities may be living at the minimum energy flux needed for prokaryotic cells to subsist.”
The reason the oxygen penetrates so deep is that the sedimentation process is very slow. The bacteria in the deepest layers packed a lunch box while dinosaurs still roamed Earth, and they’re still living off it, as new organic material is unlikely to have entered their realm since then. Since they live so slowly, it’s probable that individual cells are really, really old. This is obviously interesting because life wears down the living, and so the bacteria might have quirky adaptations to be able to repair themselves. It should be noted that no one has studied these bacteria directly, though, so we don’t know (yet) exactly how they work.