In order to understand the degradation potential of plastics in the marine environment, microorganisms that preferentially colonize and interact with plastic surfaces, as opposed to generalists ...potentially colonising everything, need to be identified. Accordingly, it was hypothesized that i.) plastic "specific" microorganisms are closely attached to the polymeric surface and ii.) that specificity of plastics biofilms are rather related to members of the rare biosphere. To answer these hypotheses, a three phased experiment to stepwise uncover closely attached microbes was conducted. In Phase 1, nine chemically distinct plastic films and glass were incubated in situ for 21 months in a seawater flow through system. In Phase 2, a high-pressure water jet treatment technique was used to remove the upper biofilm layers to further, in Phase 3, enrich a plastic "specific" community. To proof whether microbes colonizing different plastics are distinct from each other and from other inert hard substrates, the bacterial communities of these different substrates were analysed using 16S rRNA gene tag sequencing. Our findings indicate that tightly attached microorganisms account to the rare biosphere and suggest the presence of plastic "specific" microorganisms/assemblages which could benefit from the given plastic properties or at least grow under limited carbon resources.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
To understand the ecological impacts of the “Plastisphere”, those microbes need to be identified that preferentially colonize and interact with synthetic polymer surfaces, as opposed to general ...surface colonizers. It was hypothesized that the microbial biofilm composition varies distinctly between different substrates. A long-term incubation experiment was conducted (15month) with nine different synthetic polymer films as substrate as well as glass using a natural seawater flow-through system. To identify colonizing microorganisms, 16S and 18SrRNA gene tag sequencing was performed. The microbial biofilms of these diverse artificial surfaces were visualized via scanning electron microscopy. Biofilm communities attached to synthetic polymers are distinct from glass associated biofilms; apparently a more general marine biofilm core community serves as shared core among all synthetic polymers rather than a specific synthetic polymer community. Nevertheless, characteristic and discriminatory taxa of significantly different biofilm communities were identified, indicating their specificity to a given substrate.
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•Statistically robust analysis of biofilms on distinct synthetic polymers.•Proof that synthetic polymer and glass biofilms differ significantly.•Differences of biofilms between synthetic polymers are generally low.•Significant differences between diverse synthetic polymer biofilms were observed.•A general marine biofilm core community serves as shared core among all substrates.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
A process of global importance in carbon cycling is the remineralization of algae biomass by heterotrophic bacteria, most notably during massive marine algae blooms. Such blooms can trigger secondary ...blooms of planktonic bacteria that consist of swift successions of distinct bacterial clades, most prominently members of the Flavobacteriia, Gammaproteobacteria and the alphaproteobacterial Roseobacter clade. We investigated such successions during spring phytoplankton blooms in the southern North Sea (German Bight) for four consecutive years. Dense sampling and high-resolution taxonomic analyses allowed the detection of recurring patterns down to the genus level. Metagenome analyses also revealed recurrent patterns at the functional level, in particular with respect to algal polysaccharide degradation genes. We, therefore, hypothesize that even though there is substantial inter-annual variation between spring phytoplankton blooms, the accompanying succession of bacterial clades is largely governed by deterministic principles such as substrate-induced forcing.
The formation of sinking particles in the ocean, which promote carbon sequestration into deeper water and sediments, involves algal polysaccharides acting as an adhesive, binding together molecules, ...cells and minerals. These as yet unidentified adhesive polysaccharides must resist degradation by bacterial enzymes or else they dissolve and particles disassemble before exporting carbon. Here, using monoclonal antibodies as analytical tools, we trace the abundance of 27 polysaccharide epitopes in dissolved and particulate organic matter during a series of diatom blooms in the North Sea, and discover a fucose-containing sulphated polysaccharide (FCSP) that resists enzymatic degradation, accumulates and aggregates. Previously only known as a macroalgal polysaccharide, we find FCSP to be secreted by several globally abundant diatom species including the genera Chaetoceros and Thalassiosira. These findings provide evidence for a novel polysaccharide candidate to contribute to carbon sequestration in the ocean.
Phytoplankton blooms characterize temperate ocean margin zones in spring. We investigated the bacterioplankton response to a diatom bloom in the North Sea and observed a dynamic succession of ...populations at genus-level resolution. Taxonomically distinct expressions of carbohydrate-active enzymes (transporters; in particular, TonB-dependent transporters) and phosphate acquisition strategies were found, indicating that distinct populations of Bacteroidetes, Gammaproteobacteria, and Alphaproteobacteria are specialized for successive decomposition of algal-derived organic matter. Our results suggest that algal substrate availability provided a series of ecological niches in which specialized populations could bloom. This reveals how planktonic species, despite their seemingly homogeneous habitat, can evade extinction by direct competition.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
It is generally recognized that phages are a mortality factor for their bacterial hosts. This could be particularly true in spring phytoplankton blooms, which are known to be closely followed by a ...highly specialized bacterial community. We hypothesized that phages modulate these dense heterotrophic bacteria successions following phytoplankton blooms. In this study, we focused on Flavobacteriia, because they are main responders during these blooms and have an important role in the degradation of polysaccharides. A cultivation-based approach was used, obtaining 44 lytic flavobacterial phages (flavophages), representing twelve new species from two viral realms. Taxonomic analysis allowed us to delineate ten new phage genera and ten new families, from which nine and four, respectively, had no previously cultivated representatives. Genomic analysis predicted various life styles and genomic replication strategies. A likely eukaryote-associated host habitat was reflected in the gene content of some of the flavophages. Detection in cellular metagenomes and by direct-plating showed that part of these phages were actively replicating in the environment during the 2018 spring bloom. Furthermore, CRISPR/Cas spacers and re-isolation during two consecutive years suggested that, at least part of the new flavophages are stable components of the microbial community in the North Sea. Together, our results indicate that these diverse flavophages have the potential to modulate their respective host populations.
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NUK, SBMB, SBNM, UL, UM, UPUK
An increase in human Vibrio spp. infections has been linked to climate change related events, in particular to seawater warming and heatwaves. However, there is a distinct lack of research of ...pathogenic Vibrio spp. occurrences in the temperate North Sea, one of the fastest warming seas globally. Particularly in the German Bight, Vibrio investigations are still scarce. This study focuses on the spatio-temporal quantification and pathogenic characterization of V. parahaemolyticus, V. vulnificus and V. cholerae over the course of 14 months. Species-specific MPN-PCR (Most probable number – polymerase chain reaction) conducted on selectively enriched surface water samples revealed seasonal patterns of all three species with increased abundances during summer months. The extended period of warm seawater coincided with prolonged Vibrio spp. occurrences in the German Bight. Temperature and nitrite were the factors explaining variations in Vibrio spp. abundances after generalized additive mixed models. The specific detection of pathogenic markers via PCR revealed trh-positive V. parahaemolyticus, pathogenic V. vulnificus (nanA, manIIA, PRXII) and V. cholerae serotype O139 presence. Additionally, spatio-temporally varying virulence profiles of V. cholerae with multiple accessory virulence-associated genes, such as the El Tor variant hemolysin (hlyAET), acyltransferase of the repeats-in-toxin cluster (rtxC), Vibrio 7th pandemic island II (VSP-II), Type III Secretion System (TTSS) and the Cholix Toxin (chxA) were detected. Overall, this study highlights that environmental human pathogenic Vibrio spp. comprise a reservoir of virulence-associated genes in the German Bight, especially in estuarine regions. Due to their known vast genetic plasticity, we point to the possible emergence of highly pathogenic V. cholerae strains. Particularly, the presence of V. cholerae serotype O139 is unusual and needs urgent continuous surveillance. Given the predictions of further warming and more frequent heatwave events, human pathogenic Vibrio spp. should be seriously considered as a developing risk to human health in the German Bight.
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•Temperature and nitrite are the main drivers of Vibrio spp. abundances.•V. cholerae Serotype O139 detected for the first time in this region.•Multiple virulence-associated genes occur throughout the German Bight.•Climate change expected to increase abundance and prolong occurrence of Vibrio spp.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Rivers are transport systems and supply adjacent ecosystems with nutrients. They also serve human well-being, for example as a source of food. Microorganism biodiversity is an important parameter for ...the ecological balance of river ecosystems. Despite the knowledge that fungi are key players in freshwater nutrient cycling and food webs, data on planktonic fungi of streams with higher stream order are scarce. This study aims to fill this knowledge gap by a fungi-specific 18S ribosomal RNA (rRNA) gene tag sequencing approach, investigating mycoplankton diversity in the Elbe River along a transect from shallow freshwater, to the estuary and river plume down to the adjacent marine waters (sections of seventh stream order number). Using multivariate analyses and the quantitative process estimates (QPEs) method, questions (i) of how mycoplankton communities as part of the river continuum change along the transect, (ii) what factors, spatial and environmental, play a role, and (iii) what assembly processes, such as selection or dispersion, operate along the transect, were addressed. The partitioning of mycoplankton communities into three significant distant biomes was mainly driven by local environmental conditions that were partly under spatial control. The assembly processes underlying the biomes also differed significantly. Thus, variable selection dominated the upstream sections, while undominated processes like ecological drift dominated the sections close to the river mouth and beyond. Dispersal played a minor role. The results suggest that the ecological versatility of the mycoplankton communities changes along the transect as response, for example, to a drastic change from an autotrophic to a heterotrophic system caused by an abrupt increase in the river depth. Furthermore, a significant salinity-dependent occurrence of diverse basal fungal groups was observed, with no clade found exclusively in marine waters. These results provide an important framework to help understand patterns of riverine mycoplankton communities and serve as basis for a further in-depth work so that fungi, as an important ecological organism group, can be integrated into models of, e.g., usage-balance considerations of rivers.
As the atmospheric CO(2) concentration rises, more CO(2) will dissolve in the oceans, leading to a reduction in pH. Effects of ocean acidification on bacterial communities have mainly been studied in ...biologically complex systems, in which indirect effects, mediated through food web interactions, come into play. These approaches come close to nature but suffer from low replication and neglect seasonality. To comprehensively investigate direct pH effects, we conducted highly-replicated laboratory acidification experiments with the natural bacterial community from Helgoland Roads (North Sea). Seasonal variability was accounted for by repeating the experiment four times (spring, summer, autumn, winter). Three dilution approaches were used to select for different ecological strategies, i.e. fast-growing or low-nutrient adapted bacteria. The pH levels investigated were in situ seawater pH (8.15-8.22), pH 7.82 and pH 7.67, representing the present-day situation and two acidification scenarios projected for the North Sea for the year 2100. In all seasons, both automated ribosomal intergenic spacer analysis and 16S ribosomal amplicon pyrosequencing revealed pH-dependent community shifts for two of the dilution approaches. Bacteria susceptible to changes in pH were different members of Gammaproteobacteria, Flavobacteriaceae, Rhodobacteraceae, Campylobacteraceae and further less abundant groups. Their specific response to reduced pH was often context-dependent. Bacterial abundance was not influenced by pH. Our findings suggest that already moderate changes in pH have the potential to cause compositional shifts, depending on the community assembly and environmental factors. By identifying pH-susceptible groups, this study provides insights for more directed, in-depth community analyses in large-scale and long-term experiments.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The dynamics of coastal marine microbial communities are driven by seasonally changing abiotic and biotic factors as well as by rapidly occurring short-term changes such as river fresh water influxes ...or phytoplankton blooms. We examined the variability of the free-living bacterioplankton at Helgoland Roads (German Bight, North Sea) over a period of one year with high temporal and taxonomic resolution to reveal variation patterns and main influencing factors. 16S rRNA gene tag sequencing of the bacterioplankton community hints at annual recurrence and resilience of few main taxa belonging to Alphaproteobacteria, Betaproteobacteria, Flavobacteriia, Acidimicrobiia and Thermoplasmata. Multiple regression analyses with various environmental factors revealed changes in water current patterns and resulting phytoplankton blooms as the main driving factors for short-term variation and temperature as the overlying factor for seasonal variation. Comparison of bacterioplankton successions during spring and summer phytoplankton blooms revealed the same dominating Flavobacteriia operational taxonomic units (OTUs) but shifts in Roseobacter related OTUs (Alphaproteobacteria) and SAR92 clade members (Gammaproteobacteria). Network analysis suggests that during spring and summer phytoplankton blooms temperature-dependent guilds are formed. In conclusion, our data imply that short-term bacterioplankton successions in response to phytoplankton blooms are indirectly affected by temperature, which is a major niche-defining factor in the German Bight.
Bacterioplankton succession in response to phytoplankton blooms is indirectly affected by temperature, and thus temperature-dependent guilds are formed during spring and summer phytoplankton blooms.
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