Life at the Edge: Define the Boundaries of the Nitrogen Cycle in the Extreme Antarctic Environments

Natural ecosystems harbour a tremendous diversity of microorganisms able to transform nitrogen N compounds in ways that make it available for biological production1,2. However, our understanding on how the extreme nature of physical environments affects and limits N biogeochemical processes and consequently life distribution, by excluding or not essential N microbial pathways, is still unclear3,4.

Antartica Cold Deserts ACD, are considered to be one of the most remote natural environments on Earth, with extremely dry and oligotrophic conditions3 and thought for a long time to be a region where life approaches its environmental limits5. In such harsh conditions, microorganisms dominate and drive all biological processes in the system 6, however it still remains a paradox how biological communities are supported in such an oligotrophic environment3,7. Previous studies from our research team suggested that prokaryotic communities involved in N-fixation and ammonia oxidation may assume a keystone function in promoting the pumping of N into the ACD8,10,11,12,13. In this project we propose to extend previous observations in a comprehensive and detailed study on the functionality of the microbial communities involved in N biogeochemical processes, to understand N sources and recycling pathways in ACD ecosystems. Our goals will be addressed by studying the distribution, frequency and diversity of the microbial communities and target genes involved in the N biogeochemical processes across different ACD located in the Transantarctic Mountains. Next generation sequence NGS technology based on 16S rRNA-gene and shotgun metagenomics sequencing analysis will be used as major methodological tools. In situ rate measurements using isotope pairing techniques and transcriptomic analysis during field campaigns will be complemented with laboratory-based experiments in Environmental Chambers, where the response of the microbial communities involved in N biogeochemistry to environmental gradients will be monitored. Environmental and biological data integration will be achieved by applying general exploratory analysis as well as spatial interpolation and pattern mining tools, delivering a set of models concerning the significant abiotic factors that drives the distribution and constrain the activity of the N biogeochemical pathways in ACD.

Covering all major steps of N cycle across different terrestrial habitats in DVs, this project will enable to outline the limits of N biogeochemical activity of resident microbial communities as well as to understand in what way different N transformations are established according to shifts in the microbial functional potential influenced by abiotic factors. It will represent an important breakthrough regarding ecosystem functioning, giving new insights on the ecological role of microorganisms in the regulation of N cycle in one of the most extreme environments on Earth.