It has been argued that this might be due to the dynamics selleck chemical of environmental

changes, favoring certain species at certain time points. In a previous study, we used an integrated proteogenomic approach to investigate the bacterioplankton’s response to a diatom-dominated spring phytoplankton bloom in German Bight of the North Sea in the year 2009 (Teeling et al., 2012). We observed a tight succession of distinct blooming bacterial clades that was most pronounced for Flavobacteria (genera Ulvibacter, Formosa, and Polaribacter) and Gammaproteobacteria (genus Reinekea and SAR92 clade species) ( Fig. 1). The combined analysis of metagenomes and metaproteomes from different time points throughout the succession uncovered differences in the gene repertoires and expression profiles of distinct clades. These differences suggest that the clades

are specialized on different substrates, and that the succession was mainly a bottom-up controlled (i.e. substrate-driven) and not a top-down controlled (i.e. predator-driven) process. In the current study we analyzed two metatranscriptomes from the same sampling campaign, one from before (31/03/2009) and one from amidst (14/04/2009) the phytoplankton bloom to provide complementary insights into the community composition, as well as the gene expression of dominating community members. We sequenced the metatranscriptomes (mRNA transcribed into cDNA) of both samples using Roche 454 pyrosequencing, and additionally the March sample Trichostatin A supplier was sequenced with Illumina technology. We furthermore compared metatranscriptome-based biodiversity estimates with biodiversity data derived from pyrotag sequencing and previous metagenome 16S rDNA analyses. In addition, we interrelated 16S rDNA expression levels with taxon abundance estimates of distinct taxa and used this as a proxy to identify the metabolically most active community members. Combining these analyses allowed us to reproduce the key aspects of the previous

study and provided new insights into the ecological strategies of the most Uroporphyrinogen III synthase abundant community members. Sample collection was carried out as part of the MIMAS (Microbial Interaction in Marine Systems) project as described previously (Teeling et al., 2012). In brief, surface water was collected from the site ‘Kabeltonne’ off the coast of the island Helgoland in the German Bight of the North Sea (54°11.18′N, 7°54.00′E) on 11/02/2009 and weekly from the 31/03/2009 until 24/11/2009. The samples (360 L) were collected at a depth of about 0.5 to 1 m, and processed immediately. The water samples were pre-filtered through 10 μm and 3 μm pore-size filters onto 0.2 μm pore-size filters, from which material was harvested for nucleic acids extraction. For DNA 25 L and for RNA 10 L of the original water sample were filtered on four filters each. All filters were stored at -80 °C until use.