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Symbioses between eukaryotes and nitrogen-fixing cyanobacteria off Brazil

Symbioses between eukaryotes and nitrogen-fixing cyanobacteria off Brazil

Seminar at the Pontifical University of Chile in Santiago and the Universidad de Concepcion (ECODIM mini symposium).
Based on our paper in ISME: https://www.nature.com/articles/s41396-018-0050-z

Daniel Vaulot

April 06, 2018
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  1. Catherine Ribeiro, Adriana Lopes dos Santos, Dominique, Marie,
    Frederico Brandini, Daniel Vaulot
    Station Biologique de Roscoff, UPMC et CNRS, France
    Universidade de São Paulo, Brasil
    Symbiosis
    between nitrogen-fixing bacteria and eukaryotes
    on the continental shelf of Brazil

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  2. N2 fixation in the ocean
    Trichodesmium

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  3. Nitrogen fixing cyanabacteria
    nifH gene

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  4. Identifying UCYN-A

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  5. UCYN-A lacks critical genes

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  6. UCYN-A occurs in Symbiosis with Eukaryote
    UCYN-A
    Eukaryote
    NanoSIMS
    N15 enrichment

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  8. The plot thickens
    16S rRNA

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  9. Genome of UCYN-A1 vs A2
    86% similarity at AA level
    135 genes

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  10. The plot thickens again...
    Three types of UCYN-A Different hosts
    A1
    A2
    A3 ?

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  11. Always more clades... A1 -> A6

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  12. UCYN-A is major
    contributor to N2
    fixation
    Trichodesmium
    UCYN-A

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  13. Distribution of hosts
    A1 Host
    A2 Host
    CARBOM

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  14. CARBOM cruise - Continental shelf Brazil
    SACW
    BC

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  15. TR1 TR2
    Pico and Nanoeukaryotes
    Picoeukaryotes
    Nanoeukaryotes

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  16. 16S rRNA from sorted cells
    Chrysophyc
    Clade B2
    Isochrysidales
    Braarudosphaeraceae
    EF051761 - Chrysochromulina campanulifera - strain UIO J10
    HM133350 - Biosope T60 16S OXY107.017
    HM133259 - Biosope T41 16S PLA491.033
    LK391826 - Ochromonas sp. - strain F933
    HM133175 - Biosope T35 16S PLA491.033
    St.98 surf PEUK clone F4
    St.TRICHO surf PEUK clone B1
    St.98 surf NEUK clone C2
    HM133499 - Biosope T84 16S PLA491.026
    HM133324 - Biosope T58 16S PLA491.010
    LN735407 - Emiliania huxleyi - strain RCC 2941
    KP282836 - Gephyrocapsa muellerae - strain RCC3862
    LK391825 - Chrysochromulina apheles - strain F929
    St.98 surf PEUK clone E5
    HM133343 - Biosope T60 16S OXY107.004
    HM133380 - Biosope T60 16S PLA491.021
    HM133420 - Biosope T65 16S.38a
    AB847984 - Braarudosphaera bigelowii - strain TMRscBb1
    2
    2
    7 15
    picoplankton sequences
    nanoplankton sequences
    69
    100
    99
    57
    88
    92
    99
    90
    100

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  17. Strategy
    • Samples preserved with DMSO 10%
    • Two fractions sorted by flow cytometry : Pico and Nano (56 samples)
    • Two genes
    – nuclear 18S rRNA (V4)
    – nifH
    • 1 run Ilumina MiSeq 2*250 bp
    • Analysis with Mothur
    • Assignement : PR2, BLAST

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  18. 18S rRNA classes

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  19. 18S rRNA OTUs

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  20. 18S rRNA classes

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  21. Bray distance clustering based on major 18S OTUs
    Dinos Mam Prym Diatoms Chrys
    UCYN-A1 host
    Ostreo + Bathy
    Prymnesiophyceae
    Prorocentrum

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  22. Picoeukaryote communities are structured by
    the environment

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  23. nifH diversity
    A1
    A3
    Tricho
    A2
    A4

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  24. A1
    A3
    Tricho
    A2
    Bray distance clustering based on major nifH OTUs
    A4

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  25. 18S vs nifH

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  26. Network analysis using 18S rRNA and nifH
    "Pico" network
    SparCC

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  27. Conclusion
    On the shelf off Brazil
    • Two major types photosynthetic eukaryotic communities :
    – Braarudosphaeraceae
    – Ostreococcus + Bathycoccus
    • Nitrogen fixers
    – UCYN-A is dominant nitrogen fixer : A1, A2, A3, A4
    • Network analysis
    – Recover A1 and A2 associations
    – A4 could have same host than A2 (Braarudosphaera)
    – A3 ?

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  28. Breaking news ... "Pomacytosis"

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  29. Breaking news ...
    UCYN-A
    Eukaryote

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  30. Breaking news ...

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