Species Capable of Growth at Pressures Ranging Over 5 Orders of Magnitude, from the Surface of Mars (10 Pa) to Deep Oceans (10 Pa) in the Solar System.

Several permanently cold solar system bodies are being investigated with regard to their potential habitability, including Mars and icy moons. In such locations, microbial life would have to cope with low temperatures and both high and low pressures, ranging from ∼10 to 10 Pa on the surface of Mars to upward of ∼10-10 Pa in the subsurface oceans of icy moons. The bacterial genus consists of species that were previously shown to be capable of growth in the absence of oxygen at low temperatures and at either low pressure or high pressure, but to date the entire pressure range of the genus has not been explored. In the present study, we subjected 14 strains representing 11 species to cultivation in a complex liquid medium under anaerobic conditions at 2°C and at a range of pressures spanning 5 orders of magnitude, from 10 to 10 Pa. Eleven of the 14 strains showed measurable growth rates at all pressures tested, representing the first demonstration of terrestrial life forms capable of growth under such a wide range of pressures. These findings expand the physical boundaries of the capabilities of life to occur in extreme extraterrestrial environments.