16.09.2013 - (idw) Max-Planck-Institut fr marine Mikrobiologie

Researchers from the Max Planck Institute for Marine Microbiology and their colleagues from the Royal Netherlands Institute for Sea Research uncover how viruses regulate carbon release from the alga Phaeocystis globosa. They published their discovery in the ISME Journal.

Phaeocystis globosa is an alga forming harmful blooms in the coastal waters of the North Sea. The decay of algal biomass at the end of the bloom leads to massive release of organic matter, which in turn stimulates the growth of a variety of heterotrophic gamma- and alpha-proteobacteria. An important source of mortality for these algae are lytic P. globosa viruses. We therefore investigated how algal viral infection and subsequent lysis affects the community structure of the associated bacteria, explains Dr. Abdul R. Sheik, the lead author of this study. In control experiments they showed that the bacterial composition of infected algal cultures differed from non-infected cultures after 5 hours. In order to understand the underlying mechanism Dr. Sheik and colleagues monitored the uptake of the released organic material by the bacterioplankton using isotopically-labeled algal biomass (with isotopes of nitrogen and carbon). Assimilation of the substrate was quantified in single bacterial cells using imaging secondary ion mass spectrometry (nanoSIMS) with a sub-micrometer spatial resolution. Surprisingly, we saw colonization of algal cells and uptake of labeled carbon and nitrogen by Alteromonas cells long before the algal cells lysed, explains Abdul Sheik. This suggests that infected but still intact algae can already shape the microbial community composition by excretion or leakage of organic matter.

These results reveal a new pathway in the transfer of algal biomass to the bacterioplankton and, in a larger picture, new mechanism of retaining carbon in the euphotic zone.

Further Information Dr. Abdul R. Sheik, +352 46 66 44 5746, abdul.sheik@uni.lu Prof. Dr. Marcel Kuypers, +49 421 2028602, mkuypers@mpi-bremen.de

Press office Dr. Manfred Schloesser, +49 421 2028704, mschloes@mpi-bremen.de

Involved institutions Max Planck Institute for Marine Microbiology, Bremen Royal Netherlands Institute for Sea Research, Texel Institute for Biodiversity and Ecosystems Dynamics, Amsterdam

Original article Responses of the coastal bacterial community to viral infection of the algae Phaeocystis globosa Abdul R. Sheik, Corina P. D. Brussaard, Gaute Lavik, Phyllis Lam, Niculina Musat, Andreas Krupke, Sten Littmann, Marc Strous and Marcel M. M. Kuypers doi: 10.1038/ismej.2013.135 Weitere Informationen:http://www.mpi-bremen.de Webpage of the Max Planck Institute for Marine Microbiology

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Viruses and algae in the Sea