Use of organic exudates from two polar diatoms by bacterial isolates from the Arctic Ocean

• Published in: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
• Main Authors: Tisserand, Lucas, Dadaglio, Laëtitia, Intertaglia, Laurent, Catala, Philippe, Panagiotopoulos, Christos, Obernosterer, Ingrid, Joux, Fabien
• Other Authors: Laboratoire d'Océanographie Microbienne (LOMIC), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Observatoire océanologique de Banyuls (OOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire océanologique de Banyuls (OOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: Arctic Ocean; Diatoms; Dissolved organic exudates; Biodegradation; Bacterial isolation; Bacterial diversity; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDE.MCG]Environmental Sciences/Global Changes; Baffin Bay; Baffin; Global warming; Sea ice
• Online Access: https://hal.science/hal-02916320; https://hal.science/hal-02916320/document; https://hal.science/hal-02916320/file/Preprint_final_PTRSA_2020.pdf; https://doi.org/10.1098/rsta.2019.0356

International audience Global warming affects primary producers in the Arctic, with potential consequences on the bacterial community composition through the consumption of microalgae-derived dissolved organic matter. To determine the degree of specificity in the use of an exudate by bacterial taxa, we used simple microalgae-bacteria model systems. We isolated 92 bacterial strains from the sea ice bottom and the water column in spring-summer in the Baffin Bay (Arctic Ocean). The isolates were grouped into 42 species belonging to Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. 40 strains were tested for their capacity to grow on the exudate from two Arctic diatoms. Most of the strains tested (78 %) were able to grow on the exudate from the pelagic diatom Chaetoceros neogracilis and 33 % were able to use the exudate from the sea ice diatom Fragilariopsis cylindrus. 17.5% of the strains were not able to grow with any exudate while 27.5 % of the strains were able to use both types of exudates. All strains belonging to Flavobacteriia (n = 10) were able to use the DOM provided by C. neogracilis, and this exudate sustained a growth capacity of up to 100 times higher than diluted marine broth medium, of two Pseudomonas sp. strains and one Sulfitobacter strain. The variable bioavailability of exudates to bacterial strains 27 highlights the potential role of microalgae in shaping the bacterial community composition.