Piezophilic adaptation in deep sea amphipods

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The deep ocean (below 2000m) represents the last ecological frontier on the planet. It accounts for >86% of the ocean biosphere, yet we know remarkably little about the organisms that live and thrive there. Recent developments in engineering technology has allowed us to begin to explore and sample the oceans right down to full ocean depth at close to 11000 metres at the bottom of the Mariana Trench. This has given us a lot of insight into what organisms are found at the deepest depths of our oceans, but what is still a big unknown is how these organisms can survive the crushing pressures that should otherwise compromise, or indeed prevent, many basic cellular processes. Clearly, deep ocean organisms must have accumulated a number of evolutionary adaptations that means their biochemistry is not affected in the same way by pressure as terrestrial or shallow water species. It is the underlying aim of this project to identify what these adaptations are. The "front line" of attack by high pressure on biochemical processes is on the RNA molecules that carry the "blueprint" for all of the proteins that an organism must make throughout life, and are also directly involved in protein construction. We think that deep ocean organisms have adapted to high pressures by having a suite of RNA molecules that are structurally more stable, and likewise code for proteins with a higher stability when they form. We can test these ideas by comparing the nucleotide sequences of lots of different genes in organisms that occupy the full range of ocean depths. We will focus on a group of cosmopolitan amphipod crustaceans that occur in all the oceans and at all depths. What is unique about our project is we have already collected the samples we need to undertake this type of analysis, which is a non-trivial task and would otherwise be preclusively expensive and time-consuming.We predict we will see the signatures of selection operating on lots of genes that help chaperone biochemical reactions in those amphipod species occurring at deeper depth, and suggest that pressure will constrain the ability to change sequence through mutation. Moreover we expect to see that the RNA sequences in deeper species generally have a higher stability by having a higher ratio of the more stable building blocks. We will also move beyond just looking at RNA sequence and also examine the 3D structures these molecules make. Again we predict there are certain conformations that the RNA molecules will tend to form (termed hairpins) in the deeper species, and there will some building blocks in the RNA molecules that act like bridge keystones for maintaining structure that will be conserved across the different amphipod species we are examining.Overall, this project can provide the first insights into some of the evolutionary processes that define which species are present in the deep sea, and conversely explain why some species are absent. This can tell us a lot about the rules that govern the spatial distribution of organisms across the planet and in different habitats, and provide some information about how communities in different areas will be affected by a changing environment.