Biology subjects

Kuhlisch, C.

Publications and source records attributed to Kuhlisch, C..

4 recordsLinked to original sources

bioRxiv2022

Novel lipid biomarkers for algal resistance to viral infection in the ocean

Marine viruses play a key role in regulating phytoplankton populations, greatly affecting the biogeochemical cycling of major nutrients in the ocean. Resistance to viral infection has been reported for various phytoplankton species under laboratory conditions. Nevertheless, the occurrence of resistant cells in natural populations is underexplored due to the lack of sensitive tools to detect these rare phenotypes. Consequently, our current understanding of the ecological importance of resistance and its underlying mechanisms is limited. Here, we sought to discover lipid biomarkers for the resistance of the bloom-forming alga Emiliania huxleyi to its specific virus, E. huxleyi virus (EhV). We identified novel glycosphingolipids (GSLs) that characterize resistant E. huxleyi strains by applying an untargeted lipidomics approach. Further, we detected these lipid biomarkers in E. huxleyi isolates that were recently collected from E. huxleyi blooms and used them to detect resistant cells in the demise phase of an open ocean E. huxleyi bloom. Lastly, we show that the GSL composition of E. huxleyi cultures that recover following infection and gain resistance to the virus resembles that of resistant strains. These findings highlight the metabolic plasticity and co-evolution of the GSL biosynthetic pathway and underscore its central part in this host-virus arms race.

microbiology↗

bioRxiv2022

Bacterial lifestyle switch in response to algal metabolites

Unicellular algae, termed phytoplankton, greatly impact the marine environment by serving as the basis of marine food webs and by playing central roles in biogeochemical cycling of elements. The interactions between phytoplankton and heterotrophic bacteria affect the fitness of both partners. It is becoming increasingly recognized that metabolic exchange determines the nature of such interactions, but the underlying molecular mechanisms remain underexplored. Here, we investigated the molecular and metabolic basis for the bacterial lifestyle switch, from coexistence to pathogenicity, in Sulfitobacter D7 during its interaction with Emiliania huxleyi, a cosmopolitan bloom-forming phytoplankter. To unravel the bacterial lifestyle switch, we profiled bacterial transcriptomes in response to infochemicals derived from algae in exponential and stationary growth, which induced the Sulfitobacter D7 coexistence and pathogenicity lifestyles, respectively. We found that algal dimethylsulfoniopropionate (DMSP) was a pivotal signaling molecule that mediated the transition between the lifestyles. However, the coexisting and pathogenic lifestyles were evident only in the presence of additional algal metabolites. In the pathogenic mode, Sulfitobacter D7 upregulated flagellar motility and many transport systems, presumably to maximize assimilation of E. huxleyi-derived metabolites released by algal cells upon cell death. Specifically, we discovered that algae-produced benzoate promoted the growth of Sulfitobacter D7, and negated the DMSP-inducing lifestyle switch to pathogenicity, demonstrating that benzoate is important for maintaining the coexistence of algae and bacteria. We propose that bacteria can sense the physiological status of the algal host through changes in the metabolic composition, which will determine the bacterial lifestyle during the interactions. Significance StatementMicroorganisms in the marine environment play crucial roles in the regulation of Earths climate and elemental cycling. Understanding microbial interactions and the metabolic exchange that drives them is necessary for disentangling the complexity of the marine ecosystem. Here we demonstrate how the opportunistic pathogen Sulfitobacter D7 switches its lifestyle from coexistence to pathogenicity in response to metabolites released by Emiliania huxleyi, a bloom-forming unicellular alga. By mapping bacterial transcriptional profiles, we show that the algal metabolite dimethylsulfoniopropionate (DMSP), an important signaling molecule in the marine environment, is essential for the bacterial lifestyle switch. However, the activity of DMSP depended on additional algal signals. This work emphasizes how metabolic crosstalk can influence the nature and fate of microbial interactions, which have cascading effects on large-scale oceanic processes.

microbiology↗

bioRxiv2021

Viral infection switches the balance between bacterial and eukaryotic recyclers of organic matter during algal blooms

Algal blooms are hotspots of marine primary production and play central roles in microbial ecology and global nutrient cycling. When blooms collapse, organic carbon is transferred to higher trophic levels, microbial respiration or sinking in proportions that depend on the dominant mortality agent. Viral infection can lead to bloom termination, but its impact on the fate of carbon remains an open question. Here, we characterized the consequences of viral infection on the microbiome composition and biogeochemical landscape of marine ecosystems by conducting a large-scale mesocosm experiment. Moniroting of seven induced coccolithophore blooms, which showed different degrees of viral infection, revealed that only high levels of viral infection caused significant shifts in the composition of free-living bacterial and eukaryotic assemblages. Intriguingly, viral infection favored the growth of eukaryotic heterotrophs (thraustochytrids) over bacteria as potential recyclers of organic matter. By combining modeling and quantification of active viral infection at a single-cell resolution, we estimate that viral infection can increase per-cell rates of extracellular carbon release by 2-4.5 fold. This happened via production of acidic polysaccharides and particulate inorganic carbon, two major contributors to carbon sinking into the deep ocean. These results reveal the impact of viral infection on the fate of carbon through microbial recyclers of organic matter in large-scale coccolithophore blooms.

microbiology↗

bioRxiv2020

Viral infection of algal blooms leaves a halogenated footprint on the dissolved organic matter in the ocean

Algal blooms are important hotspots of primary production in the ocean, forming the basis of the marine food web and fueling the pool of dissolved organic matter (DOM)1, which is the largest global inventory of reduced carbon and a market place for metabolic exchange in the ocean2. Marine viruses are key players in controlling algal bloom demise and act as major biogeochemical drivers of nutrient cycling and metabolic fluxes by shunting algal biomass from higher trophic levels to the DOM pool, a process termed the viral shunt3,4. Nevertheless, the metabolic composition of virus-induced DOM (vDOM) in the marine environment is unknown. To decode the metabolic footprint of the viral shunt, we induced a bloom of the ecologically important alga Emiliania huxleyi in the natural environment, and followed its succession using an untargeted exometabolomics approach. Here we show that algal bloom succession induces extensive and dynamic changes in the exometabolic landscape, especially during bloom demise. By correlating to a specific viral gene marker, we discovered a set of novel chlorine-iodine-containing metabolites that were induced by viral infection and copiously released during bloom demise. We further detected several of these chloro-iodo metabolites in virus-infected open ocean blooms of E. huxleyi, supporting their use as sensitive biomarkers for virus-induced demise in the natural environment. Therefore, we propose halogenation to be a hallmark of the E. huxleyi vDOM, providing insights into the profound metabolic consequences of viral infection for the marine DOM pool.

microbiology↗