Extremophiles, organisms who experience optimum growth in conditions lethal to most others, and extremotolerant organisms who may not necessarily be extremophiles yet can natheless thrive in such conditions, are of extreme interest to astrobiologists.
(And Extremotolerant Organisms)
Acidophiles & Hyperacidotolerant, Near-Acidophilic Neutriphiles
This group includes organisms capable of thriving in hyperacidic conditions, most of which have an optimal growth pH of 5 or lower (OGpH≤5), although a few have an OGpH slightly above this (e.g., Nanoarchaeum equitans, OGpH=6) but can nonetheless be found flourishing in hyperacidic environments (pH=0.5-1.5).
This group includes organisms with an optimal growth pH of 10 or higher (OGpH≥10)
Also known as piezophiles, this group includes organisms with an optimal growth pressure of 10 Mpa (~100 bar) or higher (≥98.6 atmospheres).
This group includes organisms which require sodium chloride for their growth and reproduction...
This group includes organisms with an optimum growth temperature of ≥80°C.
This group includes organisms who can thrive and reproduce at water activity lower than that typical for most life on Earth (aw≤0.8)
Also known as psychrophiles, this group includes organisms with an optimal growth temperature equal to or less than ten degrees celsius (OGT≤10°C).
(And Polyextremotolerant Organisms)
This group includes polyextremophiles who are simultaneously both thermophilic and acidophilic.
This group includes polyextremophiles who are simultaneously both thermophilic and barophilic.