DMSP signals the end for E.hux?

Roseobacter interactions with phytoplankton blooms range from cooperative to pathogenic and are probably mediated by info-chemicals.  Dimethylsulphoniopropionate (DMSP) and its breakdown products generate cloud condensation nuclei, act as a chemoattractant for seabirds and potentially also for bacteria seeking sulphur and carbon sources.  Emiliania huxleyi (E.hux) forms massive blooms and is a significant producer of DMSP which is consumed by co-occurring Sulfitobacter.  

E.hux blooms are known to be mitigated through viral lysis and grazing but Barak-Gavish et al. (2018) postulated that bacteria may also have a role.  They showed that E.hux populations were indeed decimated when cocultured with Sulfitobacter D7.  However, E.hux monocultures and cocultures with the co-occurring Marinobacter D6 were unaffected.  Resistant E.hux strains became more susceptible when DMSP was added to Sulfitobacter cocultures showing that bacterial growth and algicidal interaction appear to be mediated by DMSP concentration.

It is valuable to reveal a potential new player in bloom mediation but, given a 40% mortality in the control sample, it is possible that other pathogens were at work such as viruses which passed through cell sorting as endosymbionts. Given the importance of E.hux to the carbon-sink process more work is needed to understand how Sulfitobacter, and other pathogens, interact in bloom communities and the signal molecules involved. 

BARAK-GAVISH, N., FRADA, M. J., KU, C., LEE, P. A., DITULLIO, G. R., MALITSKY, S., AHARONI, A., GREEN, S. J., ROTKOPF, R., KARTVELISHVILY, E., SHEYN, U., SCHATZ, D. & VARDI, A. 2018. Bacterial virulence against an oceanic bloom-forming phytoplankter is mediated by algal DMSP. Science Advances, 4.

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