Ever since the origin of life on Earth, bacteria and Archaea have been far richer in species than any other group of organisms. But it is difficult to assess their full biodiversity because most species of bacteria and Archaea cannot be grown in the laboratory. For example, Persephonella bacteria – aptly named after the Greek goddess of hell, after their extreme habitat – can only survive around thermal vents on the ocean floor at depths of 2 to 3 km, under extreme pressure, in complete darkness, and in superheated water of up to 300 °C.
Sayaka Mino and colleagues from the University of Hokkaido used deep-sea submersibles to sample Persephonella hydrogeniphila from the Okinawa Trough between Japan and China and the South Mariana Trough south of Japan.
They show that this species is highly diverse, with pronounced genetic and metabolic differences between the two ocean troughs. This implies that both populations have been long isolated from each other, presumably because P. hydrogeniphila cannot easily spread across parts of the ocean floor that lack thermal vents.
This study confirms that we have hardly begun to sample the enormous biodiversity at the ocean floor – we currently know more about the surface of Mars.
Extreme_Microbiology - DOI:10.3389/fmicb.2013.00107