Link between dissolved organic matter and diversity of heterotrophic marine bacteria

• Main Author: Landa, Marine
• Other Authors: Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire océanologique de Banyuls (OOB), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie, Ecole doctorale des sciences de l'environnement, Ingrid Obernosterer, Stéphane Blain
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2013
• Subjects: Bacterial diversity; phytoplankton DOM; continuous cultures; pyrosequencing; Mediterranean Sea; Southern Ocean; Diversité bactérienne; MOD phytoplanctonique; cultures continues; pyroséquençage; mer Méditerranée; océan Austral; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry; Molecular Biology/Molecular biology; [SDV.BBM.GTP]Life Sciences [q-bio]/Biochemistry; Molecular Biology/Genomics [q-bio.GN]; Austral
• Online Access: https://theses.hal.science/tel-03923812; https://theses.hal.science/tel-03923812/document; https://theses.hal.science/tel-03923812/file/Manuscrit_the%CC%80se_Landa_2013.pdf

In the marine environment, heterotrophic bacteria strongly depend on dissolved organic matter (DOM). How the composition, concentration and availability of DOM affect the structure and diversity of bacterial populations remains however an open question. In this thesis, we performed three continuous culture experiments in the Mediterranean Sea and the Southern Ocean, to address three questions: 1) How does an increase in DOM affect bacterial diversity? 2) What is the phylogenetic and structural response of heterotrophic bacteria to chemically distinct DOM? 3) Can changes in DOM supply explain changes in bacterial diversity during an in situ phytoplankton bloom? To address these questions, we grew natural bacterial communities in various DOM conditions and examined bacterial diversity by 454 Tag pyrosequencing of 16S rRNA genes. In the Mediterranean Sea, we observed that an increase in the supply of DOM resulted in an increase in bacterial richness and phylogenetic diversity, and in moderate changes in the phylogenetic composition of bacterial communities. By contrast, two phytoplankton DOM sources that varied in their chemical composition sustained bacterial communities with different levels of diversity but did not affect their phylogenetic composition. In the Southern Ocean, the addition of diatom-derived DOM increased the diversity of dominant groups and this was coupled to taxonomic shifts. These bacterial groups were also observed in situ, associated with a phytoplankton bloom induced by natural iron fertilization (KEOPS2). Taken together, our results demonstrate the shaping effect of DOM on bacterial diversity, both in experimental studies and in situ. En milieu marin, les bactéries hétérotrophes dépendent de la matière organique dissoute (MOD). L’effet des caractéristiques de cette matière sur la structure et la diversité des populations bactériennes demeure flou. Durant cette thèse, trois études en culture continue ont été réalisées en mer Méditerranée et dans l’océan Austral pour répondre à trois ...