Chapter 46 : Extreme High-Pressure Marine Environments

Abstract:

The observation that the vast majority of Earth’s microorganisms reside in extreme aquatic environments, given the immense volume of the deep ocean, is a simple fact. Some combination of extreme temperature, pressure, food supply, acidity, redox conditions, or even water activity describes the norm, not the rarity, for aquatic microbial habitats. This chapter provides some history, current trends, and specific examples of strategies and experimental protocols for studying microorganisms (Bacteria and Archaea) that inhabit the largest volume of extreme (or any inhabited) environment on the planet, the pressurized deep ocean and its sub-seafloor realm. Although few scientists have ready access to submersible operations in the deep sea or even to standard sampling expeditions by surface ships, the new investigator can find established researchers forthcoming with expertise, field samples, or cultured strains. Yet another variant on the theme of end-point experiments at high temperatures and pressures is the recent development in the Jørgensen laboratory of a high-pressure thermal gradient block, generally patterned after the system described for low-temperature, high-pressure research. The problem for extreme deep-sea environments, as elsewhere, lies with the available approaches to measuring activity, not with limitations to deep-sea sampling or seafloor experimentation. The latter are limited only by resources (and perhaps motivation), since a wide variety of sampling gear and instrumentation, including pressure retaining devices, are available for in situ study of deep-sea extremophiles.