Ecological and Evolutionary Functional Genomics (EuroEEFG)

Abstract

The deep ocean covers two-thirds of our planet and teams with microbial life. Understanding the roles of deep-sea microbial communities is therefore essential for understanding global biogeochemical cycling, which in turn is pivotal to all other forms of life. The breakthrough discovery that marine bathypelagic realms are significant zones of autotrophic CO2 fixation, i.e. areas of dark ocean primary production, is perhaps the most exciting application of modern molecular approaches in the field of deep-sea microbiology. Considering that deep-sea environment represents the biggest ecosystem on our planet, it is surprising that the contribution of bathypelagic chemolithoautotrophic production to the microbial foodweb and to global carbon cycling in general has not been studied yet. After all, it represents a major CO2 sink in the System Earth. Recently, members of Marine Group I of Thaumarchaeota have been identified to be potentially involved in deep-sea chemolithotrophic production of organic carbon. Several independent studies have estimated the global archaeal dissolved inorganic carbon (DIC)-fixation rate of 4-8 x 1011 kg C yr-1. This newly fixed carbon represents a substrate for a largely unknown deep-sea foodweb including microbial and metazoan members. Besides autotrophy, marine Thaumarchaeota which are very abundant in the deep-sea, are likely to play a pivotal role in the ocean’s nitrogen cycle because they perform the first step in the nitrification process, namely the conversion of ammonia to nitrite. Thus, it seems that these creatures are capable to grow using ammonia as its energy source and CO2 as its carbon source. However, a direct link between deep ocean dark CO2 fixation and the identity of the organisms or assemblages involved in this process has not been established so far and is thus one of the main goals of the DEEP_C proposal.

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