EMPANADAS investigates particle microbial colonization in the dark ocean

PI Mar Benavides and Christian Tamburini

The ocean mitigates climate change through CO2 fixation by photosynthetic phytoplankton at the sunlit surface ocean, followed by the aggregation of their biomass into particles which sink into the deep ocean. Sinking aggregates act as hotspots attracting the surrounding microbial life. The architecture, diversity and activity of particle colonizing microbes is largely unknown, but is bound to have important consequences on particle remineralization and thus the contribution of the ocean to mitigate climate change.

The goal of this project is to develop and implement novel techniques to characterize particle-attached microbes via advanced microscopy approaches:

1)  Cell viability: We will visualize active cells attached to particles by testing their membrane integrity using cell viability kits.

2)  Taxonomic and functional diversity: We will identify particle-attached microbes via fluorescent in situ hybridization (FISH) approaches using taxa targeted probes.

3)  Metabolism: The metabolism of particle-attached microbes will be assessed by the Bioorthogonal non-canonical amino acid tagging assay (BONCAT).

4)  Colonizing architecture: To visualize the distribution of microbes on marine particles we will embed particles in resins (Tissue Tek and epoxy resins), which will be subsequently sliced using microtomes. The visualization of different layers will allow 3D reconstruction to identify the architecture or colonizing microbes on particles.

The samples will be obtained from the PARTY cruise ("remineralisation des PARticules marines et Transfert vers les abYsses") which will take place in the Mediterranean Sea onboard the R/V Tethys II in May 2021.