Project description:<p>Algal blooms are hotspots of primary production in the ocean, forming the basis of the marine food web and fueling the dissolved organic matter (DOM) pool. Marine viruses are key players in controlling algal bloom demise, thereby diverting algal biomass from higher trophic levels to the DOM pool, a process termed the ‘viral shunt’. To decode the metabolic footprint of the ‘viral shunt’ in the marine environment, we induced a bloom of <em>Emiliania huxleyi</em> and followed its succession using an untargeted exometabolomics approach. Here, we show that algal bloom succession induces dynamic changes in the exometabolic landscape. We discovered a set of novel chlorine-iodine-containing metabolites that were induced by viral infection and released during bloom demise. These metabolites were further detected in virus-infected oceanic <em>E. huxleyi</em> blooms. Therefore, we propose that halogenation with both chlorine and iodine is a distinct hallmark of the virus-induced DOM of <em>E. huxleyi</em>, providing insights into the metabolic consequences of the ‘viral shunt’ for marine DOM.</p>
Project description:Peptides were identified during degradation of the diatom Thalassiosira weissflogii with and without the use of the enzyme trypsin. This allows comparison of protein degradation occurring within the experiment (no trypsin added; peptides already present due to in situ degradation) and the protein still available for future degradation (peptides released from protein when trypsin is added during analysis). Over the 12-day degradation experiment 31% of the particulate organic carbon was depleted and there was no preferential degradation of the overall protein pool. However, there was distinct differentiation in the cellular location, secondary structure and modifications of the peptides that were either degraded or remained. During the initial period of rapid algal decay and bacterial growth, intracellular components from the cytoplasm were selectively consumed, resulting in the accumulation of membrane-associated proteins and peptides in the detrital pool. Accompanying this was an increase in the importance of membrane-bound ɑ-helix motifs. At the end of the 12 day experiment, the natural bacterial assemblage was focusing on degradation of membrane-associated proteins, which was the dominant source of peptides in both the residual pool (released by trypsin) and the actively degraded pool (no trypsin added). Methylated arginine, a post-translationally modified amino acid that is produced within the diatom prior to senescence, is found in high amounts within the detrital peptide pool, suggesting a link between in-cell modification and resistance to immediate degradation. Another modification - asparagine deamidation - appears to occur during degradation and deamidated peptides also accumulate within the detritus. The bacterial community decomposing the algal material was rich in proteobacteria, and employed a growth approach focusing on accumulation of solubilized material across their membranes and on DNA replication. At this early stage of diagenesis, no changes in bulk amino acids (THAA) were observed, yet a peptidomic approach allowed us to observe the differential changes in diatom protein preservation by discriminating between intracellular location, secondary structure, and modifications status.
2021-12-20 | PXD027843 | Pride
Project description:Bacterial community dynamics during a harmful algal bloom of Heterosigma akashiwo
| PRJNA669545 | ENA
Project description:Spatiotemporal changes of bacterial and cyanobacterial communities during an algal bloom
Project description:Lytic viruses have been implicated in the massive cellular lysis observed during algal blooms, through which they assume a prominent role in oceanic carbon and nutrient flows. Despite their impact on biogeochemical cycling, the transcriptional dynamics of these important oceanic events is still poorly understood. Here, we employ an oligonucleotide microarray to monitor host (Emiliania huxleyi) and virus (coccolithovirus) transcriptomic features during the course of E. huxleyi blooms induced in seawater-based mesocosm enclosures. Host bloom development and subsequent coccolithovirus infection was associated with a major shift in transcriptional profile. In addition to the expected metabolic requirements typically associated with viral infection (amino acid and nucleotide metabolism, as well as transcription- and replication-associated functions), the results strongly suggest that the manipulation of lipid metabolism plays a fundamental role during host-virus interaction. The results herein reveal the scale, so far massively underestimated, of the transcriptional domination that occurs during coccolithovirus infection in the natural environment.