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

Transcript

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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