Nitrogen transformations in microbial mats: Implications for microbial evolution on Earth and the search for life elsewhere
NASA Ames Research Center
Microbial mats are thought to have originated around 3.7 billion years ago in the areas around submarine hydrothermal vents, which also believed to exist on Europa, Enceladus and earlier on Mars. They are stratified communities with layers of microorganisms and sediments. It is assumed that most of biogeochemical processes occur within microbial mats as they comprise a very heterogeneous microbial community. Nitrogen usually limits growth in marine environment and therefore, N-cycling processes represents especial interest when investigating ecosystem functioning. The aim of this study is a determination of a complete nitrogen budget with its key players for two photosynthetic microbial mats. The research uses a combination of stable isotope labeling, microbial ecological techniques, and bioinformatic tools not previously deployed in microbial mats. The relationship between bacterial abundance and activity in terms of nitrogen is revealed and examined in dependence of environmental parameters such as salinity. The results show the presence of most of nitrogen cycling bacteria and processes, with the absolute prevalence of nitrogen fixation and assimilation. The results of this work help us to improve our understanding of the cycle of the element most responsible for limiting the production of biomass on Earth and extend an ability to use nitrogen containing compounds in our search for life elsewhere.
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