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:


Daniel Vaulot

April 06, 2018


  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
  2. N2 fixation in the ocean Trichodesmium

  3. Nitrogen fixing cyanabacteria nifH gene

  4. Identifying UCYN-A

  5. UCYN-A lacks critical genes

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

  7. None
  8. The plot thickens 16S rRNA

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

    135 genes
  10. The plot thickens again... Three types of UCYN-A Different hosts

    A1 A2 A3 ?
  11. Always more clades... A1 -> A6

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

  13. Distribution of hosts A1 Host A2 Host CARBOM

  14. CARBOM cruise - Continental shelf Brazil SACW BC

  15. TR1 TR2 Pico and Nanoeukaryotes Picoeukaryotes Nanoeukaryotes

  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
  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
  18. 18S rRNA classes

  19. 18S rRNA OTUs

  20. 18S rRNA classes

  21. Bray distance clustering based on major 18S OTUs Dinos Mam

    Prym Diatoms Chrys UCYN-A1 host Ostreo + Bathy Prymnesiophyceae Prorocentrum
  22. Picoeukaryote communities are structured by the environment

  23. nifH diversity A1 A3 Tricho A2 A4

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

    nifH OTUs A4
  25. 18S vs nifH

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

  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 ?
  28. Breaking news ... "Pomacytosis"

  29. Breaking news ... UCYN-A Eukaryote

  30. Breaking news ...