Deep Sea Microbial Ecology

The deep sea, at depths greater than 1,000 meters, is marked by cold temperatures of 2–3 degrees Celsius, immense hydrostatic pressure that increases by approximately 1 atmosphere every 10 meters, and low nutrient levels.

Piezotolerant microbes are those that can tolerate high-pressure conditions and remain viable under them, such as members of the genus Colwellia.

On the other hand, true piezophiles, such as Moritella species, grow and survive best under high pressure through specific cellular mechanisms.

For example, to maintain membrane fluidity and protein stability under high pressure, piezophiles increase the proportion of unsaturated fatty acids in their membranes. Some species express pressure-regulated proteins such as OmpH through pressure-sensitive transcription systems.

Below 2,000 meters, sediments harbour sulfate reducers and methane-oxidizing organisms, along with other microbes adapted to extreme energy limitation.

This scarcity results in cell densities being far lower than in shallower regions.