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  • 11
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    Online Resource
    Strains of the Harmful Cyanobacterium Microcystis aeruginosa Differ in Gene Expression and Activity of Inorganic Carbon Uptake Systems at Elevated CO 2 Levels
    American Society for Microbiology ; 2015
    In:  Applied and Environmental Microbiology Vol. 81, No. 22 ( 2015-11-15), p. 7730-7739
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 81, No. 22 ( 2015-11-15), p. 7730-7739
    Abstract: Cyanobacteria are generally assumed to be effective competitors at low CO 2 levels because of their efficient CO 2 -concentrating mechanism (CCM), and yet how bloom-forming cyanobacteria respond to rising CO 2 concentrations is less clear. Here, we investigate changes in CCM gene expression at ambient CO 2 (400 ppm) and elevated CO 2 (1,100 ppm) in six strains of the harmful cyanobacterium Microcystis . All strains downregulated cmpA encoding the high-affinity bicarbonate uptake system BCT1, whereas both the low- and high-affinity CO 2 uptake genes were expressed constitutively. Four strains downregulated the bicarbonate uptake genes bicA and/or sbtA , whereas two strains showed constitutive expression of the bicA - sbtA operon. In one of the latter strains, a transposon insert in bicA caused low bicA and sbtA transcript levels, which made this strain solely dependent on BCT1 for bicarbonate uptake. Activity measurements of the inorganic carbon (C i ) uptake systems confirmed the CCM gene expression results. Interestingly, genes encoding the RuBisCO enzyme, structural carboxysome components, and carbonic anhydrases were not regulated. Hence, Microcystis mainly regulates the initial uptake of inorganic carbon, which might be an effective strategy for a species experiencing strongly fluctuating C i concentrations. Our results show that CCM gene regulation of Microcystis varies among strains. The observed genetic and phenotypic variation in CCM responses may offer an important template for natural selection, leading to major changes in the genetic composition of harmful cyanobacterial blooms at elevated CO 2 .
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/AEM.02295-15
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2015
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 12
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    Interspecific protection against oxidative stress: green algae protect harmful cyanobacteria against hydrogen peroxide
    Wiley ; 2021
    In:  Environmental Microbiology Vol. 23, No. 5 ( 2021-05), p. 2404-2419
    Details
    In: Environmental Microbiology, Wiley, Vol. 23, No. 5 ( 2021-05), p. 2404-2419
    Abstract: Oceanographic studies have shown that heterotrophic bacteria can protect marine cyanobacteria against oxidative stress caused by hydrogen peroxide (H 2 O 2 ). Could a similar interspecific protection play a role in freshwater ecosystems? In a series of laboratory experiments and two lake treatments, we demonstrate that freshwater cyanobacteria are sensitive to H 2 O 2 but can be protected by less‐sensitive species such as green algae. Our laboratory results show that green algae degrade H 2 O 2 much faster than cyanobacteria. Consequently, the cyanobacterium Microcystis was able to survive at higher H 2 O 2 concentrations in mixtures with the green alga Chlorella than in monoculture. Interestingly, even the lysate of destructed Chlorella was capable to protect Microcystis , indicating a two‐component H 2 O 2 degradation system in which Chlorella provided antioxidant enzymes and Microcystis the reductants. The level of interspecific protection provided to Microcystis depended on the density of Chlorella . These findings have implications for the mitigation of toxic cyanobacterial blooms, which threaten the water quality of many eutrophic lakes and reservoirs worldwide. In several lakes, H 2 O 2 has been successfully applied to suppress cyanobacterial blooms. Our results demonstrate that high densities of green algae can interfere with these lake treatments, as they may rapidly degrade the added H 2 O 2 and thereby protect the bloom‐forming cyanobacteria.
    Type of Medium: Online Resource
    ISSN: 1462-2912 , 1462-2920
    URL: Issue
    URL: Article
    DOI: 10.1111/emi.v23.5
    DOI: 10.1111/1462-2920.15429
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2020213-1
    SSG: 12
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  • 13
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    Diversity and phylogeny of Baltic Sea picocyanobacteria inferred from their ITS and phycobiliprotein operons
    Wiley ; 2008
    In:  Environmental Microbiology Vol. 10, No. 1 ( 2008-01), p. 174-188
    Details
    In: Environmental Microbiology, Wiley, Vol. 10, No. 1 ( 2008-01), p. 174-188
    Abstract: Picocyanobacteria of the genus Synechococcus span a range of different colours, from red strains rich in phycoerythrin (PE) to green strains rich in phycocyanin (PC). Here, we show that coexistence of red and green picocyanobacteria in the Baltic Sea is widespread. The diversity and phylogeny of red and green picocyanobacteria was analysed using three different genes: 16S rRNA‐ITS, the cpeBA operon of the red PE pigment and the cpcBA operon of the green PC pigment. Sequencing of 209 clones showed that Baltic Sea picocyanobacteria exhibit high levels of microdiversity. The partial nucleotide sequences of the cpcBA and cpeBA operons from the clone libraries of the Baltic Sea revealed two distinct phylogenetic clades: one clade containing mainly sequences from cultured PC‐rich picocyanobacteria, while the other contains only sequences from cultivated PE‐rich strains. A third clade of phycourobilin (PUB) containing strains of PE‐rich Synechococcus spp. did not contain sequences from the Baltic Sea clone libraries. These findings differ from previously published phylogenies based on 16S rRNA gene analysis. Our data suggest that, in terms of their pigmentation, Synechococcus spp. represent three different lineages occupying different ecological niches in the underwater light spectrum. Strains from different lineages can coexist in light environments that overlap with their light absorption spectra.
    Type of Medium: Online Resource
    ISSN: 1462-2912 , 1462-2920
    URL: Issue
    URL: Article
    DOI: 10.1111/emi.2008.10.issue-1
    DOI: 10.1111/j.1462-2920.2007.01442.x
    Language: English
    Publisher: Wiley
    Publication Date: 2008
    detail.hit.zdb_id: 2020213-1
    SSG: 12
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  • 14
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    From Ecological Stoichiometry to Biochemical Composition: Variation in N and P Supply Alters Key Biosynthetic Rates in Marine Phytoplankton
    Frontiers Media SA ; 2017
    In:  Frontiers in Microbiology Vol. 8 ( 2017-07-12)
    Details
    In: Frontiers in Microbiology, Frontiers Media SA, Vol. 8 ( 2017-07-12)
    Type of Medium: Online Resource
    ISSN: 1664-302X
    URL: Article
    DOI: 10.3389/fmicb.2017.01299
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2017
    detail.hit.zdb_id: 2587354-4
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  • 15
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    Risso's dolphins perform spin dives to target deep-dwelling prey
    The Royal Society ; 2021
    In:  Royal Society Open Science Vol. 8, No. 12 ( 2021-12)
    Details
    In: Royal Society Open Science, The Royal Society, Vol. 8, No. 12 ( 2021-12)
    Abstract: Foraging decisions of deep-diving cetaceans can provide fundamental insight into food web dynamics of the deep pelagic ocean. Cetacean optimal foraging entails a tight balance between oxygen-conserving dive strategies and access to deep-dwelling prey of sufficient energetic reward. Risso's dolphins ( Grampus griseus ) displayed a thus far unknown dive strategy, which we termed the spin dive. Dives started with intense stroking and right-sided lateral rotation. This remarkable behaviour resulted in a rapid descent. By tracking the fine-scale foraging behaviour of seven tagged individuals, matched with prey layer recordings, we tested the hypothesis that spin dives are foraging dives targeting deep-dwelling prey. Hunting depth traced the diel movement of the deep scattering layer, a dense aggregation of prey, that resides deep during the day and near-surface at night. Individuals shifted their foraging strategy from deep spin dives to shallow non-spin dives around dusk. Spin dives were significantly faster, steeper and deeper than non-spin dives, effectively minimizing transit time to bountiful mesopelagic prey, and were focused on periods when the migratory prey might be easier to catch. Hence, whereas Risso's dolphins were mostly shallow, nocturnal foragers, their spin dives enabled extended and rewarding diurnal foraging on deep-dwelling prey.
    Type of Medium: Online Resource
    ISSN: 2054-5703
    URL: Article
    DOI: 10.1098/rsos.202320
    Language: English
    Publisher: The Royal Society
    Publication Date: 2021
    detail.hit.zdb_id: 2787755-3
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  • 16
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    Resilience of Microbial Communities after Hydrogen Peroxide Treatment of a Eutrophic Lake to Suppress Harmful Cyanobacterial Blooms
    MDPI AG ; 2021
    In:  Microorganisms Vol. 9, No. 7 ( 2021-07-13), p. 1495-
    Details
    In: Microorganisms, MDPI AG, Vol. 9, No. 7 ( 2021-07-13), p. 1495-
    Abstract: Applying low concentrations of hydrogen peroxide (H2O2) to lakes is an emerging method to mitigate harmful cyanobacterial blooms. While cyanobacteria are very sensitive to H2O2, little is known about the impacts of these H2O2 treatments on other members of the microbial community. In this study, we investigated changes in microbial community composition during two lake treatments with low H2O2 concentrations (target: 2.5 mg L−1) and in two series of controlled lake incubations. The results show that the H2O2 treatments effectively suppressed the dominant cyanobacteria Aphanizomenon klebahnii, Dolichospermum sp. and, to a lesser extent, Planktothrix agardhii. Microbial community analysis revealed that several Proteobacteria (e.g., Alteromonadales, Pseudomonadales, Rhodobacterales) profited from the treatments, whereas some bacterial taxa declined (e.g., Verrucomicrobia). In particular, the taxa known to be resistant to oxidative stress (e.g., Rheinheimera) strongly increased in relative abundance during the first 24 h after H2O2 addition, but subsequently declined again. Alpha and beta diversity showed a temporary decline but recovered within a few days, demonstrating resilience of the microbial community. The predicted functionality of the microbial community revealed a temporary increase of anti-ROS defenses and glycoside hydrolases but otherwise remained stable throughout the treatments. We conclude that the use of low concentrations of H2O2 to suppress cyanobacterial blooms provides a short-term pulse disturbance but is not detrimental to lake microbial communities and their ecosystem functioning.
    Type of Medium: Online Resource
    ISSN: 2076-2607
    URL: Article
    DOI: 10.3390/microorganisms9071495
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2720891-6
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  • 17
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    Adaptive divergence in pigment composition promotes phytoplankton biodiversity
    Springer Science and Business Media LLC ; 2004
    In:  Nature Vol. 432, No. 7013 ( 2004-11), p. 104-107
    Details
    In: Nature, Springer Science and Business Media LLC, Vol. 432, No. 7013 ( 2004-11), p. 104-107
    Type of Medium: Online Resource
    ISSN: 0028-0836 , 1476-4687
    URL: Article
    DOI: 10.1038/nature03044
    RVK:
    TA 1000
    RVK:
    UA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2004
    detail.hit.zdb_id: 120714-3
    detail.hit.zdb_id: 1413423-8
    SSG: 11
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  • 18
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    The Microcystin Composition of the Cyanobacterium Planktothrix agardhii Changes toward a More Toxic Variant with Increasing Light Intensity
    American Society for Microbiology ; 2005
    In:  Applied and Environmental Microbiology Vol. 71, No. 9 ( 2005-09), p. 5177-5181
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 71, No. 9 ( 2005-09), p. 5177-5181
    Abstract: The cyanobacterium Planktothrix agardhii , which is dominant in many shallow eutrophic lakes, can produce hepatotoxic microcystins. Currently, more than 70 different microcystin variants have been described, which differ in toxicity. In this study, the effect of photon irradiance on the production of different microcystin variants by P. agardhii was investigated using light-limited turbidostats. Both the amount of the mRNA transcript of the mcyA gene and the total microcystin production rate increased with photon irradiance up to 60 μmol m −2 s −1 , but they started to decrease with irradiance greater than 100 μmol m −2 s −1 . The cellular content of total microcystin remained constant, independent of the irradiance. However, of the two main microcystin variants detected in P. agardhii , the microcystin-DeRR content decreased twofold with increased photon irradiance, whereas the microcystin-DeLR content increased threefold. Since microcystin-DeLR is considerably more toxic than microcystin-DeRR, this implies that P. agardhii becomes more toxic at high light intensities.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/AEM.71.9.5177-5181.2005
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2005
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 19
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    Competition for Light between Toxic and Nontoxic Strains of the Harmful Cyanobacterium Microcystis
    American Society for Microbiology ; 2007
    In:  Applied and Environmental Microbiology Vol. 73, No. 9 ( 2007-05), p. 2939-2946
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 73, No. 9 ( 2007-05), p. 2939-2946
    Abstract: The cyanobacterium Microcystis can produce microcystins, a family of toxins that are of major concern in water management. In several lakes, the average microcystin content per cell gradually declines from high levels at the onset of Microcystis blooms to low levels at the height of the bloom. Such seasonal dynamics might result from a succession of toxic to nontoxic strains. To investigate this hypothesis, we ran competition experiments with two toxic and two nontoxic Microcystis strains using light-limited chemostats. The population dynamics of these closely related strains were monitored by means of characteristic changes in light absorbance spectra and by PCR amplification of the rRNA internal transcribed spacer region in combination with denaturing gradient gel electrophoresis, which allowed identification and semiquantification of the competing strains. In all experiments, the toxic strains lost competition for light from nontoxic strains. As a consequence, the total microcystin concentrations in the competition experiments gradually declined. We did not find evidence for allelopathic interactions, as nontoxic strains became dominant even when toxic strains were given a major initial advantage. These findings show that, in our experiments, nontoxic strains of Microcystis were better competitors for light than toxic strains. The generality of this finding deserves further investigation with other Microcystis strains. The competitive replacement of toxic by nontoxic strains offers a plausible explanation for the gradual decrease in average toxicity per cell during the development of dense Microcystis blooms.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/AEM.02892-06
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2007
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 20
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    Comment on “Models predict planned phosphorus load reduction will make Lake Erie more toxic”
    American Association for the Advancement of Science (AAAS) ; 2022
    In:  Science Vol. 378, No. 6620 ( 2022-11-11)
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 378, No. 6620 ( 2022-11-11)
    Abstract: Hellweger et al . (Reports, 27 May 2022, pp. 1001) predict that phosphorus limitation will increase concentrations of cyanobacterial toxins in lakes. However, several molecular, physiological, and ecological mechanisms assumed in their models are poorly supported or contradicted by other studies. We conclude that their take-home message that phosphorus load reduction will make Lake Erie more toxic is seriously flawed.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.add9959
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2022
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
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