Poster De Conférence Année : 2025

New insights into the influence of temperature and nutrients on the growth of Microcystis aeruginosa and the metabolism of its phycosphere thanks to metabolomics

Résumé

Cyanobacterial blooms are a phenomenon of growing international concern, due to their potential ecological, human and economic impacts. While certain abiotic factors are known to contribute to these phenomena, the underlying ecological and physiological mechanisms remain only partially understood. Recently, some studies have highlighted the potential role of biotic interactions between heterotrophic bacteria and cyanobacteria in the phycosphere (i.e. a few tens of microns microenvironment surrounding cyanobacteria) in promoting cyanobacterial blooms. In this context, the COMIC project aims to better understand the occurrence of cyanobacterial blooms by studying cross-feeding metabolic interactions between Microcystis aeruginosa and heterotrophic bacteria through the coupling of metagenomic, meta-metabolomic and modeling approaches. More specifically, COMIC aims (i) to compare cross-feeding metabolic interactions in the phycosphere between cyanobacteria and heterotrophic bacteria in 12 strains of Microcystis and (ii) to characterize the influence of environmental factors (temperature and nutrients) on cross-feeding interactions in one strain. This internship is part of the project’s second objective. To this end, an 8-weeks experiment (i.e. 2 growth cycle) under controlled conditions is being carried out to characterize the successive influence of temperature (22 vs 30◦) and nutrient conditions (oligotrophic vs eutrophic) on cyanobacterial growth, as well as metabolism and interactions within its phycosphere. Every week, measurements of optical density, biomass, cell concentration and chlorophyll A are performed to characterize cyanobacterial growth. At the same time, the physiological state of the cyanobacteria is assessed using photosynthetic yield measurements. In addition, weekly biomass samples are taken for metabolomic analysis to study changes in microcystins production and the overall metabolism of the consortium. Biomass samples will further undergo metagenomic analysis to assess bacterial taxonomy and model metabolism and phycosphere interactions, with weekly nutrient monitoring. Overall, these investigations will contribute to gain understanding of the role of Microcystis phycosphere metabolism and metabolic interactions in cyanobacterial blooms.

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hal-05173526 , version 1 (21-07-2025)

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  • HAL Id : hal-05173526 , version 1

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Thomas Forjonel, Sylvia Moreira, Charlotte Duval, Mélissa Eon, B Marie, et al.. New insights into the influence of temperature and nutrients on the growth of Microcystis aeruginosa and the metabolism of its phycosphere thanks to metabolomics. E-TOX, May 2025, CESTAS, France. sciencesconf.org:etox2025:641286, 2025. ⟨hal-05173526⟩
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