Biology subjects

Crispi, O.

Publications and source records attributed to Crispi, O..

3 recordsLinked to original sources

bioRxiv2025

Effect of cellular nutrient economy on the evolution of genome size in phytoplankton

The origin of genome size variation remains a central question in evolutionary biology. Previous analyses suggest that the energetic costs of small insertions and deletions (indels) influence genome size by altering the cellular energy budget. Here, we present a theoretical framework for genome evolution in phytoplankton--the main producers of the sunlit ocean--whose growth depends on nutrient availability. We derive an expression for the selection coefficient on indels as a function of the minimum amount of nutrient inside the cell. Parameter estimates indicate that 1-bp indels can be counterselected in phytoplankton with minimal nutrient requirements. We then test three predictions of nutrient-driven selection on genome evolution. Altogether, this model provides a quantitative and mathematical basis for the genome streamlining hypothesis.

ecology↗

bioRxiv2024

Unveiling Crocosphaera responses to phosphorus depletion: insights from genome analysis and functional characterization

Unicellular, nitrogen-fixing cyanobacteria (UCYN) thrive and support primary production in oligotrophic oceans, playing a significant role in the marine nitrogen cycle. Crocosphaera sp, a model for studying marine nitrogen fixation, is adapted to low phosphate (Pi) conditions. Yet, how Crocosphaera copes with Pi depletion is rather poorly understood. We present genomics analysis of Pi stress-responsive genes in this genus, encompassing six C. watsonii genomes and two strains isolated in coastal environments, C. subtropica and C. chwakensis. We identified genes involved in Pi signaling, uptake, and dissolved organic phosphorus (DOP) hydrolysis. Results showed different genetic potentials to cope with Pi scarcity between the Crocosphaera strains. Physiological monitoring of cultures of C. watsonii WH8501 exposed to Pi depletion highlighted a capacity to divide several times and survive for a few more days, albeit with a skewed C:N:P stoichiometry. Upon addition of DOP, cultures efficiently recovered to a growth rate and cell composition equivalent to those observed under favorable conditions. The concomitant transcription analysis revealed diel expression patterns of Pi-related genes and endogenous clock genes, suggesting a possible circadian regulation. Our data deepen our understanding of the growth strategies Crocosphaera employs in Pi-limited environments, offering broader insights into microbial resilience in marine ecosystems.

microbiology↗

bioRxiv2023

Tagging of water masses with covariance of trace metals and prokaryotic taxa in the Southern Ocean

Marine microbes are strongly interrelated to trace metals in the ocean. How the availability of trace metals selects for prokaryotic taxa and the potential feedbacks of microbial processes on the trace metal distribution in the ocean remains poorly understood. We investigate here the potential reciprocal links between diverse prokaryotic taxa and iron (Fe), manganese (Mn), copper (Cu), Nickel (Ni) as well as apparent oxygen utilization (AOU) across 12 well-defined water masses in the Southern Indian Ocean (SWINGS-South West Indian Ocean GEOTRACES GS02 Section cruise). Applying Partial Least Square Regression (PLSR) analysis we show that the water masses are associated with particular latent vectors that are a combination of the spatial distribution of prokaryotic taxa, trace elements and AOU. This approach provides novel insights on the potential interactions between prokaryotic taxa and trace metals in relation to organic matter remineralization in distinct water masses of the ocean.

microbiology↗