[B-BG01] Earth and Planetary Science Frontiers for Life and Global Environment

[BBG01-01] Comparative analysis of iron rich hot springs: implications for Earth’s ancient-biosphere metabolic potential

*Fatima Li-Hau¹, Shawn E McGlynn^1,2, Yuichiro Ueno^2,1, Mayuko Nakagawa^2,1, Takeshi Kakegawa³, Luce M Ward⁴ (1.Earth-Life Science Institute, 2.Tokyo Institute of Technology, 3.Tohoku University, 4.Smith College)

Keywords:early earth, microbial ecology, iron oxidation, hot springs

The ecology of Earth’s early biosphere remains largely unconstrained. One possible strategy is the study of analogue environments, which might shed light on which organisms and metabolic modes were present in early Earth environments. Iron rich hot springs on Earth today are representative of environments around the time of the great oxidation event, fairly abundant in Japan, but yet mostly unexplored (Ward et al., 2019; Ward et al., 2017). Here we present metagenomic and geochemical analyses aimed at elucidating the metabolic potential of the communities of five iron rich hot springs of Japan. Our findings reveal the presence of complete carbon, nitrogen and sulfur cycles in all springs however, the organisms involved in key transformations differed between them. Iron oxidizers from the Zetaproteobacteria and Betaproteobacteria phyla appear to be the main primary producers despite the presence of Cyanobacteria, showing that under certain conditions, they might be important players in material cycling. Although unique taxonomic patterns exist between the springs, the overall metabolic potentials found at each were surprisingly similar. The generation of metagenome assembled genomes (MAGs) and the phylogenetic placement of key enzymes in them such as [NiFe] and [FeFe] hydrogenases and cytochromes also allow us to unravel the specific contributions of organisms to their communities. These findings highlight the importance of characterizing an environment from different approaches to have a coherent view of its ecology and allow us to glimpse at the dynamics of a yet unexplored biosphere.