Polar Microalgae: New Approaches towards Understanding Adaptations to an Extreme and Changing Environment

Abstract

Polar Regions are unique and highly prolific ecosystems characterized by extreme environmental gradients. Photosynthetic autotrophs, the base of the food web, have had to adapt physiological mechanisms to maintain growth, reproduction and metabolic activity despite environmental conditions that would shut-down cellular processes in most organisms. High latitudes are characterized by temperatures below the freezing point, complete darkness in winter and continuous light and high UV in the summer. Additionally, sea-ice, an ecological niche exploited by microbes during the long winter seasons when the ocean and land freezes over, is characterized by large salinity fluctuations, limited gas exchange, and highly oxic conditions. The last decade has been an exciting period of insights into the molecular mechanisms behind adaptation of microalgae to the cryosphere facilitated by the advancement of new scientific tools, particularly "omics" techniques. We review recent insights derived from genomics, transcriptomics, and proteomics studies. Genes, proteins and pathways identified from these highly adaptable polar microbes have far-reaching biotechnological applications. Furthermore, they may provide insights into life outside this planet, as well as glimpses into the past. High latitude regions also have disproportionately large inputs into global biogeochemical cycles and are the region most sensitive to climate change.

Figure 1

Functional groups for elevated (A) and reduced (B) proteins in F. cylindrus following a shift to high salinity. This is an example of the major functional groups associated with polar algae acclimation processes. Note that most proteins resolved on 2DE gels had predicted functions in contrast to the much larger percentage of unknown proteins in genomic and transcriptomic datasets, most likely due to gel bias towards highly abundant metabolic proteins.

Figure 2

An array of advanced, high-throughput molecular techniques is enabling a global effort to link environmental parameters to biological distributions, physiological capabilities, protein expression, metabolic functions, and biogeochemical cycles. The ultimate goal is the ability to make high resolution predictions of biogeochemical and ecosystem inputs under current and future climates. The light blue bubbles represent areas to focus future research to improve our understanding and modeling efforts. OMZ–oxygen minimum zone, PTM – post-translational modification, TF–transcription factor.