Prokaryotic MINIaturization and the hidden micrObial diversity: ecology and dispersal of ultra-small cells along the terrestrial-Marine continuum (MINIOM)

The discovery of ultra-small prokaryotes (i.e., Bacteria and Archaea) has expanded our knowledge of microbial life at the lower size limit and has evidenced that, with most commonly used sampling and sequencing techniques, we may be missing a large fraction of the actual prokaryotic diversity present in natural ecosystems. In the ocean, recent studies have unveiled that some ultra-small prokaryotic groups may be more relevant than hitherto assumed, harboring a large metabolic diversity with unknown impacts on oceanic biochemical cycles. At the same time, other ultra-small groups may be normal-sized cells that miniaturize and inactivate in response to unfavorable conditions, making up the so-called microbial “seed banks” that can reactivate if conditions change. Despite the relevance of these two groups, almost nothing is known about the biogeography and role of ultra-small prokaryotes in natural ecosystems, largely limiting our capacity to understand or even predict microbial responses to environmental changes.

MINIOM (PID2022-142480NB-I00) aims at exploring the abundance, diversity, dispersal and role of ultra-small prokaryotes (hereafter UMP) in marine ecosystems but also in coastal groundwaters connected to the sea, where these tiny microbes have been recently found to be abundant and might also play key roles in coastal marine ecosystems. MINIOM is designed as a multi-approach project that aims at getting a holistic view of the UMP fraction of microbial communities through the joint use of genomics, flow cytometry and microscopy techniques, and combining experiments and field data. All this will allow estimating the magnitude and the role in the ocean of this hidden but presumably important ultra-small fraction of prokaryotic diversity.