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Mikhail V. Zubkov - One of the best experts on this subject based on the ideXlab platform.
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Photoheterotrophy of Bacterioplankton is ubiquitous in the surface oligotrophic ocean
Progress in Oceanography, 2015Co-Authors: Claire Evans, Paola R Gómez-pereira, David J. Scanlan, Adrian Martin, Mikhail V. ZubkovAbstract:Accurate measurements in the Southern Hemisphere were obtained to test a hypothesis of the ubiquity of photoheterotrophy in the oligotrophic ocean. We present experimental results of light-enhanced uptake of methionine, leucine and ATP by Bacterioplankton during two large-scale transects of the South Atlantic. Light increased the uptake of substrates by both dominant Bacterioplankton groups, Prochlorococcus and SAR11, as well as for the bulk microbial community. Our consistent experimental evidence strongly indicates that photoheterotrophy is characteristic of dominant Bacterioplankton populations in the global oligotrophic ocean.
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Comparable light stimulation of organic nutrient uptake by SAR11 and Prochlorococcus in the North Atlantic subtropical gyre
The ISME Journal, 2013Co-Authors: Paola R Gómez-pereira, Manuela Hartmann, David J. Scanlan, Bernhard M Fuchs, Carolina Grob, Glen A Tarran, Adrian P Martin, Mikhail V. ZubkovAbstract:Subtropical oceanic gyres are the most extensive biomes on Earth where SAR11 and Prochlorococcus Bacterioplankton numerically dominate the surface waters depleted in inorganic macronutrients as well as in dissolved organic matter. In such nutrient poor conditions Bacterioplankton could become photoheterotrophic, that is, potentially enhance uptake of scarce organic molecules using the available solar radiation to energise appropriate transport systems. Here, we assessed the photoheterotrophy of the key microbial taxa in the North Atlantic oligotrophic gyre and adjacent regions using ^33P-ATP, ^3H-ATP and ^35S-methionine tracers. Light-stimulated uptake of these substrates was assessed in two dominant Bacterioplankton groups discriminated by flow cytometric sorting of tracer-labelled cells and identified using catalysed reporter deposition fluorescence in situ hybridisation. One group of cells, encompassing 48% of all Bacterioplankton, were identified as members of the SAR11 clade, whereas the other group (24% of all Bacterioplankton) was Prochlorococcus . When exposed to light, SAR11 cells took 31% more ATP and 32% more methionine, whereas the Prochlorococcus cells took 33% more ATP and 34% more methionine. Other Bacterioplankton did not demonstrate light stimulation. Thus, the SAR11 and Prochlorococcus groups, with distinctly different light-harvesting mechanisms, used light equally to enhance, by approximately one-third, the uptake of different types of organic molecules. Our findings indicate the significance of light-driven uptake of essential organic nutrients by the dominant Bacterioplankton groups in the surface waters of one of the less productive, vast regions of the world’s oceans—the oligotrophic North Atlantic subtropical gyre.
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comparable light stimulation of organic nutrient uptake by sar11 and prochlorococcus in the north atlantic subtropical gyre
The ISME Journal, 2013Co-Authors: Paola R Gomezpereira, Manuela Hartmann, David J. Scanlan, Bernhard M Fuchs, Carolina Grob, Glen A Tarran, Adrian Martin, Mikhail V. ZubkovAbstract:Subtropical oceanic gyres are the most extensive biomes on Earth where SAR11 and Prochlorococcus Bacterioplankton numerically dominate the surface waters depleted in inorganic macronutrients as well as in dissolved organic matter. In such nutrient poor conditions Bacterioplankton could become photoheterotrophic, that is, potentially enhance uptake of scarce organic molecules using the available solar radiation to energise appropriate transport systems. Here, we assessed the photoheterotrophy of the key microbial taxa in the North Atlantic oligotrophic gyre and adjacent regions using 33P-ATP, 3H-ATP and 35S-methionine tracers. Light-stimulated uptake of these substrates was assessed in two dominant Bacterioplankton groups discriminated by flow cytometric sorting of tracer-labelled cells and identified using catalysed reporter deposition fluorescence in situ hybridisation. One group of cells, encompassing 48% of all Bacterioplankton, were identified as members of the SAR11 clade, whereas the other group (24% of all Bacterioplankton) was Prochlorococcus. When exposed to light, SAR11 cells took 31% more ATP and 32% more methionine, whereas the Prochlorococcus cells took 33% more ATP and 34% more methionine. Other Bacterioplankton did not demonstrate light stimulation. Thus, the SAR11 and Prochlorococcus groups, with distinctly different light-harvesting mechanisms, used light equally to enhance, by approximately one-third, the uptake of different types of organic molecules. Our findings indicate the significance of light-driven uptake of essential organic nutrients by the dominant Bacterioplankton groups in the surface waters of one of the less productive, vast regions of the world’s oceans—the oligotrophic North Atlantic subtropical gyre.
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In situ interactions between photosynthetic picoeukaryotes and Bacterioplankton in the Atlantic Ocean: Evidence for mixotrophy
Environmental Microbiology Reports, 2013Co-Authors: Manuela Hartmann, Mikhail V. Zubkov, David J. Scanlan, Cécile LepèreAbstract:Heterotrophic Bacterioplankton, cyanobacteria and phototrophic picoeukaryotes (< 5 μm in size) numerically dominate planktonic oceanic communities. While feeding on Bacterioplankton is often attributed to aplastidic protists, recent evidence suggests that phototrophic picoeukaryotes could be important bacterivores. Here, we present direct visual evidence from the surface mixed layer of the Atlantic Ocean that Bacterioplankton are internalized by phototrophic picoeukaryotes. In situ interactions of phototrophic picoeukaryotes and Bacterioplankton (specifically Prochlorococcus cyanobacteria and the SAR11 clade) were investigated using a combination of flow cytometric cell sorting and dual tyramide signal amplification fluorescence in situ hybridization. Using this method, we observed plastidic Prymnesiophyceae and Chrysophyceae cells containing Prochlorococcus, and to a lesser extent SAR11 cells. These microscopic observations of in situ microbial trophic interactions demonstrate the frequency and likely selectivity of phototrophic picoeukaryote bacterivory in the surface mixed layer of both the North and South Atlantic subtropical gyres and adjacent equatorial region, broadening our views on the ecological role of the smallest oceanic plastidic protists.
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Effect of appendicularians and copepods on Bacterioplankton composition and growth in the English Channel
Aquatic Microbial Ecology, 2003Co-Authors: Mikhail V. Zubkov, Angel López-urrutiaAbstract:We compared the effects of the presence of the appendicularian Oikopleura dioica and the copepods Acartia clausii and Calanus helgolandicus on the coastal Bacterioplankton community off Plymouth. Mesozooplankton were added to water samples and Bacterioplankton growth was monitored by flow cytometry. Phylogenetic composition of Bacterioplankton was analysed using fluorescence in situ hybridisation (FISH) with rRNA-targeted oligonucleotide probes. The Bacterioplankton composition did not change in the presence of either appendicularians or copepods, and generally the same proportions of Bacterioplankton groups were determined. In late spring, 15 ± 2% of cells hybridised with a probe specific to the Kingdom Archaea. The majority of cells (88 ± 2%) belonged to the Kingdom Bacteria, and 86% of cells were identified using group-specific probes. The Cytophage-Flavobacterium cluster dominated the community, comprising 64 ± 0.5% of cells. The g-proteobacteria were the second abundant group, comprising 11 ± 0.5% of cells, and the SAR86 cluster of g-proteobacteria accounted for 6 ± 5%. The a-proteobacteria comprised 10 ± 5% of Bacterioplankton, and the Roseobacteria related cluster represented 9 ± 3% of cells. The reduction of Bacterioplankton growth caused by appendicularian bacterivory was 0.4 to 14% ind.-1 l-1, and the total appendicularian population could reduce bacterial growth in coastal waters in late spring-summer by up to 9%. In contrast to the appendicularians the copepods stimulated bacterial growth, and in summer the Bacterioplankton growth may be increased by up to 13% by the combined effect of dominant copepod populations. Thus, the appendicularians and copepods had an opposite but moderate effect on the Bacterioplankton growth and no effect on the Bacterioplankton composition.
Martin Søndergaard - One of the best experts on this subject based on the ideXlab platform.
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Bacterioplankton in the littoral and pelagic zones of subtropical shallow lakes
Hydrobiologia, 2010Co-Authors: David Da Motta Marques, Erik Jeppesen, Martin SøndergaardAbstract:We measured Bacterioplankton (phylotypes detected by fluorescent in situ hybridisation, morphometric forms, abundance and production) in samples collected in summer in the littoral and pelagic zones of 10 subtropical shallow lakes of contrasting area (from 13 to 80,800 ha). Compared to the pelagic zones, the littoral zones were overall characterised by higher macrophyte dominance and lower concentrations of total phosphorus and alkalinity and higher concentrations of dissolved organic carbon (DOC) and humic substances. Similarities of bacterial production and biomass turnover and density of active phylotypes and morphotype proportions were related to similarities in a set of environmental variables (including nutrients, humic substances content, predator density and phytoplankton biomass), and some additionally to lake area. Horizontal heterogeneity in Bacterioplankton variables (littoral versus pelagic) increased with lake area. Bacterioplankton biomass and production tended to be lower in the littoral zone than in the pelagic zone despite higher concentrations of DOC and humic substances. A likely explanation is higher predation on Bacterioplankton in the littoral zone, although allelophatic effects exerted by macrophytes cannot be excluded. Our results indicate that organic cycling via Bacterioplankton may be less efficient in the littoral zone than in the pelagic zone of shallow lakes.
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Production of epiphytic bacteria and Bacterioplankton in three shallow lakes
Oikos, 1999Co-Authors: J. Theil-niebsen, Martin SøndergaardAbstract:Secondary production of epiphytic bacteria and Bacterioplankton was measured from May to September in three temperate, shallow and eutrophie Danish lakes. The biomass of bacteria attached to the submerged angiosperms Ceratophyllum demersum and Potamogeton pectinatus averaged 4.3 and 3.0 μg C cm 2 and the production measured by thymidine incorporation averaged 0.28 and 0.40 μg C cm -2 h -1 . In Lake Dystrup. Ceratophyllum demersum covers about 95% of the lake area and the epiphytic bacterial production (thymidine method) per lake surface area from mid-July to early September was twice the production of the Bacterioplankton. With the lencine method the epiphytic bacterial production was seven-fold higher than the Bacterioplankton production. A 20% area cover by Potamogeton pectinatus in Lake Stigsholm resulted in an epiphytic bacterial production equal to the Bacterioplankton. The biafilms on macrophyte surfaces are hotspots with a bacterial per volume production 1000 times the Bacterioplankton. Furthermore, the growth rates of the attached bacteria were from two to four times faster than in the Bacterioplankton communities. A comparison of the twin lakes Dystrup and Ramten, respectively with and without submerged vegetation, showed Bacterioplankton production of equal magnitude despite four-fold higher phytoplankton and Bacterioplankton biomasses in Ramten. Higher bacterial growth rates in Dystrup almost compensated for the lower biomass, The total area production of the attached and free living bacteria in Dystrup was three to five times the total area production in Ramten. It is suggested that the higher Bacterioplankton growth rates in vegetated areas may be explained both by an enhanced grazing pressure and by more favorable growth conditions due to exudation of DOC from the macrophytes.
George W Kling - One of the best experts on this subject based on the ideXlab platform.
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biogeography of Bacterioplankton in lakes and streams of an arctic tundra catchment
Ecology, 2007Co-Authors: Byron C Crump, Heather E Adams, John E Hobbie, George W KlingAbstract:Bacterioplankton community composition was compared across 10 lakes and 14 streams within the catchment of Toolik Lake, a tundra lake in Arctic Alaska, during seven surveys conducted over three years using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified rDNA. Bacterioplankton communities in streams draining tundra were very different than those in streams draining lakes. Communities in streams draining lakes were similar to communities in lakes. In a connected series of lakes and streams, the stream communities changed with distance from the upstream lake and with changes in water chemistry, suggesting inoculation and dilution with bacteria from soil waters or hyporheic zones. In the same system, lakes shared similar Bacterioplankton communities (78% similar) that shifted gradually down the catchment. In contrast, unconnected lakes contained somewhat different communities (67% similar). We found evidence that dispersal influences Bacterioplankton communities via advection and dilution (mass effects) in streams, and via inoculation and subsequent growth in lakes. The spatial pattern of Bacterioplankton community composition was strongly influenced by interactions among soil water, stream, and lake environments. Our results reveal large differences in lake-specific and stream-specific bacterial community composition over restricted spatial scales (<10 km) and suggest that geographic distance and connectivity influence the distribution of Bacterioplankton communities across a landscape.
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BIOGEOGRAPHY OF Bacterioplankton IN LAKES AND STREAMS OF AN ARCTIC TUNDRA CATCHMENT
Ecology, 2007Co-Authors: Byron C Crump, Heather E Adams, John E Hobbie, George W KlingAbstract:Bacterioplankton community composition was compared across 10 lakes and 14 streams within the catchment of Toolik Lake, a tundra lake in Arctic Alaska, during seven surveys conducted over three years using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified rDNA. Bacterioplankton communities in streams draining tundra were very different than those in streams draining lakes. Communities in streams draining lakes were similar to communities in lakes. In a connected series of lakes and streams, the stream communities changed with distance from the upstream lake and with changes in water chemistry, suggesting inoculation and dilution with bacteria from soil waters or hyporheic zones. In the same system, lakes shared similar Bacterioplankton communities (78% similar) that shifted gradually down the catchment. In contrast, unconnected lakes contained somewhat different communities (67% similar). We found evidence that dispersal influences Bacterioplankton communities via advection and dilution (mass effects) in streams, and via inoculation and subsequent growth in lakes. The spatial pattern of Bacterioplankton community composition was strongly influenced by interactions among soil water, stream, and lake environments. Our results reveal large differences in lake-specific and stream-specific bacterial community composition over restricted spatial scales (
Gerhard J Herndl - One of the best experts on this subject based on the ideXlab platform.
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Relationship between Bacterioplankton Richness, Respiration, and Production in the Southern North Sea
Applied and Environmental Microbiology, 2005Co-Authors: Thomas Reinthaler, Christian Winter, Gerhard J HerndlAbstract:We investigated the relationship between Bacterioplankton production (BP), respiration (BR), and community composition measured by terminal restriction fragment length polymorphism in the southern North Sea over a seasonal cycle. Major changes in Bacterioplankton richness were apparent from April to December. While cell-specific BP decreased highly significantly with increasing Bacterioplankton richness, cell-specific BR was found to be variable along the richness gradient, suggesting that Bacterioplankton respiration is rather independent from shifts in the bacterial community composition. As a consequence, the bacterial growth efficiency [BGE = BP/(BP + BR)] was negatively related to Bacterioplankton richness, explaining ∼43% of the variation in BGE. Our results indicate that despite the observed shifts in the community composition, the main function of the Bacterioplankton, the remineralization of dissolved organic carbon to CO 2 , is rather stable.
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Production of exopolymer particles by marine Bacterioplankton under contrasting turbulence conditions
Marine Ecology Progress Series, 1999Co-Authors: Karen E. Stoderegger, Gerhard J HerndlAbstract:It has recently been shown that marine Bacterioplankton release copious amounts of capsular material as 'semi-labile' to 'refractory' dissolved organic carbon (DOC) into the ambient water. The fate of this Bacterioplankton-derived DOC remains largely unknown. Here we investigate the capability of this bacterial-derived capsular DOC to coagulate to exopolymer particles under contrasting turbulence regimes. Under high turbulence, fewer but larger particles (>2 μm in diameter) were detected, while the total exopolymer particle-mass (>0.2 μm) was higher under stagnant conditions. Under stagnant conditions most of the bacterial-derived particles remained in the size-class between 0.2 and 2 μm. The production rate of exopolymer particles was estimated to amount to about 4 amol C cell - 1 h -1 , representing about 25 % of the previously estimated Bacterioplankton DOC release of about 15 amol C cell -1 h -1 . Considering that Bacterioplankton represent the largest living surface in the ocean, the release and subsequent coagulation of Bacterioplankton-derived capsular DOC might be an important, thus far largely neglected mechanism of exopolymer particle formation in the ocean.
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Production and release of bacterial capsular material and its subsequent utilization by marine Bacterioplankton
Limnology and Oceanography, 1998Co-Authors: Karen E. Stoderegger, Gerhard J HerndlAbstract:Bacterioplankton not only take up dissolved organic carbon (DOC) and convert it into biomass and CO*, but also release DOC into the water column. Because Bacterioplankton represent the largest living surface in the world’s oceans, and most intact Bacterioplankton have a capsular envelope, we tested the hypothesis that most of the DOC released by Bacterioplankton into the water column is derived from capsular material. Therefore, the bacterial uptake of radiolabeled glucose was differentiated between incorporation into intracellular and capsular pools to obtain production estimates for capsular material. Release of the radiolabeled material into ambient water was followed and its potential as a carbon source for Bacterioplankton determined. Of the radiolabed organic carbon detected in Bacterioplankton, -55% was incorporated into intracellular material and 45% into capsular material. No significant difference was found between seawater cultures grown under P-limited and balanced nutrient conditions. After transfer of the radiolabeled bacteria into aged seawater, bacterial-derived, radiolabeled DOC was released into the ambient water at a rate of -15 amol C cell-l h-l, which corresponds to -25% of the respired C. Incorporation and respiration rates of this bacterial-derived DOC by Bacterioplankton were at least three orders of magnitude lower than the corresponding rates for glucose uptake. Incorporation of bacterial-derived DOC was only detectable when additional inorganic nutrients were added. Thus, we have evidence that Bacterioplankton are constantly renewing parts of the capsule by releasing this material into ambient water. The release rate of capsular material represents -25% of the bacterial respiration rate and suggests that a considerable portion of the oceanic DOC pool should consist. of “semi-labile” bacterial-derived DOC.
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major role of ultraviolet b in controlling Bacterioplankton growth in the surface layer of the ocean
Nature, 1993Co-Authors: Gerhard J Herndl, Gerald Mullerniklas, Jurgen FrickAbstract:THERE is evidence that the potentially harmful solar ultraviolet-B (UV-B, 280–320 mm) radiation penetrates much deeper into the ocean's water column than previously thought1,2. UV-B radiation is also responsible for photochemical degradation of refractory macromolecules into biologically labile organic compounds3,4. It thus seems reasonable to assume that UV-B radiation might influence the cycling of organic matter in the sea, which is believed to be largely mediated by Bacterioplankton5. Here we report that Bacterioplankton activity in the surface layers of the oceans is suppressed by solar radiation by about 40% in the top 5 m of the water column in nearshore waters, whereas in oligotrophic open oceans suppression might be detectable to a depth of >10 m. Bacterioplankton from near-surface (0.5 m depth) waters of a highly stratified water column were as sensitive to surface UV-B radiation as subpycnocline bacteria, indicating no adaptative mechanisms against surface solar radiation in near-surface Bacterioplankton consortia. Surface solar radiation levels also photochemically degrade bacterial extracellular enzymes. Thus elevated UV-B radiation due to the destruction of the stratospheric ozone layer might lead to reduced bacterial activity and accompanying increased concentration of labile dissolved organic matter in the surface layers of the ocean as bacterial uptake of this is retarded.
David J. Scanlan - One of the best experts on this subject based on the ideXlab platform.
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Photoheterotrophy of Bacterioplankton is ubiquitous in the surface oligotrophic ocean
Progress in Oceanography, 2015Co-Authors: Claire Evans, Paola R Gómez-pereira, David J. Scanlan, Adrian Martin, Mikhail V. ZubkovAbstract:Accurate measurements in the Southern Hemisphere were obtained to test a hypothesis of the ubiquity of photoheterotrophy in the oligotrophic ocean. We present experimental results of light-enhanced uptake of methionine, leucine and ATP by Bacterioplankton during two large-scale transects of the South Atlantic. Light increased the uptake of substrates by both dominant Bacterioplankton groups, Prochlorococcus and SAR11, as well as for the bulk microbial community. Our consistent experimental evidence strongly indicates that photoheterotrophy is characteristic of dominant Bacterioplankton populations in the global oligotrophic ocean.
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Comparable light stimulation of organic nutrient uptake by SAR11 and Prochlorococcus in the North Atlantic subtropical gyre
The ISME Journal, 2013Co-Authors: Paola R Gómez-pereira, Manuela Hartmann, David J. Scanlan, Bernhard M Fuchs, Carolina Grob, Glen A Tarran, Adrian P Martin, Mikhail V. ZubkovAbstract:Subtropical oceanic gyres are the most extensive biomes on Earth where SAR11 and Prochlorococcus Bacterioplankton numerically dominate the surface waters depleted in inorganic macronutrients as well as in dissolved organic matter. In such nutrient poor conditions Bacterioplankton could become photoheterotrophic, that is, potentially enhance uptake of scarce organic molecules using the available solar radiation to energise appropriate transport systems. Here, we assessed the photoheterotrophy of the key microbial taxa in the North Atlantic oligotrophic gyre and adjacent regions using ^33P-ATP, ^3H-ATP and ^35S-methionine tracers. Light-stimulated uptake of these substrates was assessed in two dominant Bacterioplankton groups discriminated by flow cytometric sorting of tracer-labelled cells and identified using catalysed reporter deposition fluorescence in situ hybridisation. One group of cells, encompassing 48% of all Bacterioplankton, were identified as members of the SAR11 clade, whereas the other group (24% of all Bacterioplankton) was Prochlorococcus . When exposed to light, SAR11 cells took 31% more ATP and 32% more methionine, whereas the Prochlorococcus cells took 33% more ATP and 34% more methionine. Other Bacterioplankton did not demonstrate light stimulation. Thus, the SAR11 and Prochlorococcus groups, with distinctly different light-harvesting mechanisms, used light equally to enhance, by approximately one-third, the uptake of different types of organic molecules. Our findings indicate the significance of light-driven uptake of essential organic nutrients by the dominant Bacterioplankton groups in the surface waters of one of the less productive, vast regions of the world’s oceans—the oligotrophic North Atlantic subtropical gyre.
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comparable light stimulation of organic nutrient uptake by sar11 and prochlorococcus in the north atlantic subtropical gyre
The ISME Journal, 2013Co-Authors: Paola R Gomezpereira, Manuela Hartmann, David J. Scanlan, Bernhard M Fuchs, Carolina Grob, Glen A Tarran, Adrian Martin, Mikhail V. ZubkovAbstract:Subtropical oceanic gyres are the most extensive biomes on Earth where SAR11 and Prochlorococcus Bacterioplankton numerically dominate the surface waters depleted in inorganic macronutrients as well as in dissolved organic matter. In such nutrient poor conditions Bacterioplankton could become photoheterotrophic, that is, potentially enhance uptake of scarce organic molecules using the available solar radiation to energise appropriate transport systems. Here, we assessed the photoheterotrophy of the key microbial taxa in the North Atlantic oligotrophic gyre and adjacent regions using 33P-ATP, 3H-ATP and 35S-methionine tracers. Light-stimulated uptake of these substrates was assessed in two dominant Bacterioplankton groups discriminated by flow cytometric sorting of tracer-labelled cells and identified using catalysed reporter deposition fluorescence in situ hybridisation. One group of cells, encompassing 48% of all Bacterioplankton, were identified as members of the SAR11 clade, whereas the other group (24% of all Bacterioplankton) was Prochlorococcus. When exposed to light, SAR11 cells took 31% more ATP and 32% more methionine, whereas the Prochlorococcus cells took 33% more ATP and 34% more methionine. Other Bacterioplankton did not demonstrate light stimulation. Thus, the SAR11 and Prochlorococcus groups, with distinctly different light-harvesting mechanisms, used light equally to enhance, by approximately one-third, the uptake of different types of organic molecules. Our findings indicate the significance of light-driven uptake of essential organic nutrients by the dominant Bacterioplankton groups in the surface waters of one of the less productive, vast regions of the world’s oceans—the oligotrophic North Atlantic subtropical gyre.
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In situ interactions between photosynthetic picoeukaryotes and Bacterioplankton in the Atlantic Ocean: Evidence for mixotrophy
Environmental Microbiology Reports, 2013Co-Authors: Manuela Hartmann, Mikhail V. Zubkov, David J. Scanlan, Cécile LepèreAbstract:Heterotrophic Bacterioplankton, cyanobacteria and phototrophic picoeukaryotes (< 5 μm in size) numerically dominate planktonic oceanic communities. While feeding on Bacterioplankton is often attributed to aplastidic protists, recent evidence suggests that phototrophic picoeukaryotes could be important bacterivores. Here, we present direct visual evidence from the surface mixed layer of the Atlantic Ocean that Bacterioplankton are internalized by phototrophic picoeukaryotes. In situ interactions of phototrophic picoeukaryotes and Bacterioplankton (specifically Prochlorococcus cyanobacteria and the SAR11 clade) were investigated using a combination of flow cytometric cell sorting and dual tyramide signal amplification fluorescence in situ hybridization. Using this method, we observed plastidic Prymnesiophyceae and Chrysophyceae cells containing Prochlorococcus, and to a lesser extent SAR11 cells. These microscopic observations of in situ microbial trophic interactions demonstrate the frequency and likely selectivity of phototrophic picoeukaryote bacterivory in the surface mixed layer of both the North and South Atlantic subtropical gyres and adjacent equatorial region, broadening our views on the ecological role of the smallest oceanic plastidic protists.
