Molecular structure of lipopolysaccharides of cold-adapted bacteria

Cold-adapted Gram-negative bacteria inhabit snow, ice water, and frozen grounds and are perfectly adapted to live at very low temperatures. They have evolved several adaptation strategies, some of which concern the cellular membrane. Bacterial outer membrane, that functions as a selective barrier allowing the influx of nutrients and confers protection to the cell, is also considered a primary sensor of the cold. It is well known that one of the main responses to cold concerning the cell membrane is the increment of fluidity and the upregulation of genes encoding for proteins and membrane transporters. In this context, also the lipopolysaccharides, macromolecules constituting approximately 75% of the outer surface, may be modified in their structure in response to the conditions prevailing in the environment. In this chapter, for the first time, the role played by lipopolysaccharides structures in response to cold adaptation is analyzed. Some structural features of the lipopolysaccharides are modified as a consequence of living at low temperatures, thus confirming that all the outer membrane components are involved in adaptation and survival molecular mechanisms.