Biology subjects

Benavides, M.

Publications and source records attributed to Benavides, M..

3 recordsLinked to original sources

bioRxiv2026

Tripartite synergy - Metabolic crosstalk between two bacterial mutualists and a marine microalga promotes algal fitness

Marine microalgae form major parts of phytoplankton and are highly relevant for global CO2 fixation. Although microalgae have lived together with bacteria in the oceans for billions of years, these ecosystem-relevant interactions remain largely uncharacterized. Here, we have studied biotic interactions between two marine bacteria and a marine microalga. We show that an N2-fixing Vibrio provides ammonium for Chlamydomonas sp. and a Marinobacterium. Both microorganisms cannot survive in an ammonium-free environment. In exchange, the microalga promotes the growth of both bacteria, via secretion of heat-resistant metabolites in case of Marinobacterium. Reciprocally, the Marinobacterium releases heat-resistant metabolites that stimulate algal growth and increase its photosynthetic pigments, Photosystem II quantum yield, and starch accumulation. Electron microscopy reveals a strengthened starch sheath around the algal pyrenoid and indicates a modified periplasmic space for metabolic exchange. Our data highlight a tight synergy of a marine microbial trio promoting each others growth and algal fitness.

microbiology↗

bioRxiv2021

Massive export of diazotrophs across the tropical south Pacific Ocean

Diazotrophs are widespread microorganisms that alleviate nitrogen limitation in 60% of our oceans, regulating marine productivity. Yet, their contribution to organic matter export has not been quantified, making an assessment of their impact on the biological carbon pump impossible. Here, we demonstrate that cyanobacterial and non-cyanobacterial diazotrophs are massively exported down to 1000 m-depth in the western subtropical South Pacific Ocean (WTSP), accounting for up to 52-100% of the total particulate nitrogen export fluxes. We further demonstrate that small size unicellular diazotrophs (UCYN, 1-8 {micro}m) are exported more efficiently than filamentous diazotrophs (>100-1000 {micro}m) under the form of large (>50 {micro}m) aggregates linked by an extracellular organic matrix. Beyond the WTSP, our data are supported by analysis of the Tara Oceans metagenomes collected in other ocean basins, showing that diazotrophs are systematically detected in mesopelagic waters when present at the surface. We thus conclude that diazotrophs are key players in carbon sequestration in the ocean and need to be considered in future studies to improve the accuracy of current regional and global estimates of export.

microbiology↗

bioRxiv2020

Fine scale sampling unveils diazotroph patchiness in the South Pacific Ocean

Diazotrophs are important contributors to reactive nitrogen availability in the ocean. Oceanographic cruise data accumulated along decades has revealed a heterogeneous distribution of diazotroph species at regional to global scales. However, the role of dynamic fine scale structures in distributing diazotrophs is not well understood. This is due to typical insufficient spatiotemporal resolution sampling and the lack of detailed physical studies in parallel. Here we show the distribution of five groups of diazotrophs in the South Pacific at an unprecedented resolution of 7-16 km. We find a patchy distribution of diazotrophs, with each group being differently affected by parameters describing fine scale structures. The observed variability could not have been revealed with a lower resolution sampling, highlighting the need to consider fine scale physics to resolve the distribution of diazotrophs in the ocean.

microbiology↗