ABSTRACT
Hypothesis: Deep-sea bacteria have evolved DHA chains in part as a suitable permeability barrier against Na+.
The marine world is one in which energy sources for bacteria are often highly limited and environmental conditions, such as extreme cold, create additional energy stress. The DHA-producing bacterium Moritella, described here, is found in the deepest parts of the ocean (Figure 5.1) and has evolved to live in a world dominated by multiple stresses that limit energy production and hinder energy conservation: extreme cold, high salinity, and extreme hydrostatic pressure. Indeed, deep-sea bacteria have become so specialized that they have developed a dependency on the chemical and physical environment of the deep sea. They often die when conditions are changed even slightly and can only be cultivated under stringent laboratory conditions characteristic of their deep marine world. These bacteria are classied as psychrophiles, or cold extremophiles. Moritella has evolved both conventional and novel mechanisms for capturing energy, and the purpose of this chapter is to demonstrate how DHAenriched membranes allow these cells to capitalize on the 0.5 M Na+ in seawater, for energy conservation. This mechanism of Na+ bioenergetics requires an intimate partnership with its DHA-enriched membrane.
