TY - JOUR A1 - Hackenberg, Claudia A1 - Hakanpaeae, Johanna A1 - Cai, Fei A1 - Antonyuk, Svetlana A1 - Eigner, Caroline A1 - Meissner, Sven A1 - Laitaoja, Mikko A1 - Janis, Janne A1 - Kerfeld, Cheryl A. A1 - Dittmann, Elke A1 - Lamzin, Victor S. T1 - Structural and functional insights into the unique CBS-CP12 fusion protein family in cyanobacteria JF - Proceedings of the National Academy of Sciences of the United States of America N2 - Cyanobacteria are important photosynthetic organisms inhabiting a range of dynamic environments. This phylum is distinctive among photosynthetic organisms in containing genes encoding uncharacterized cystathionine beta-synthase (CBS)-chloroplast protein (CP12) fusion proteins. These consist of two domains, each recognized as stand-alone photosynthetic regulators with different functions described in cyanobacteria (CP12) and plants (CP12 and CBSX). Here we show that CBS-CP12 fusion proteins are encoded in distinct gene neighborhoods, several unrelated to photosynthesis. Most frequently, CBS-CP12 genes are in a gene cluster with thioredoxin A (TrxA), which is prevalent in bloom-forming, marine symbiotic, and benthic mat cyanobacteria. Focusing on a CBS-CP12 from Microcystis aeruginosa PCC 7806 encoded in a gene cluster with TrxA, we reveal that the domain fusion led to the formation of a hexameric protein. We show that the CP12 domain is essential for hexamerization and contains an ordered, previously structurally uncharacterized N-terminal region. We provide evidence that CBS-CP12, while combining properties of both regulatory domains, behaves different from CP12 and plant CBSX. It does not form a ternary complex with phosphoribulokinase (PRK) and glyceraldehyde-3-phosphate dehydrogenase. Instead, CBS-CP12 decreases the activity of PRK in an AMP-dependent manner. We propose that the novel domain architecture and oligomeric state of CBS-CP12 expand its regulatory function beyond those of CP12 in cyanobacteria. KW - crystal structure KW - hexamer KW - redox KW - Microcystis aeruginosa Y1 - 2018 U6 - https://doi.org/10.1073/pnas.1806668115 SN - 0027-8424 VL - 115 IS - 27 SP - 7141 EP - 7146 PB - National Acad. of Sciences CY - Washington ER - TY - GEN A1 - des Aulnois, Maxime Georges A1 - Réveillon, Damien A1 - Robert, Elise A1 - Caruana, Amandine A1 - Briand, Enora A1 - Guljamow, Arthur A1 - Dittmann, Elke A1 - Amzil, Zouher A1 - Bormans, Myriam T1 - Salt shock responses of Microcystis revealed through physiological, transcript, and metabolomic analyses T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The transfer of Microcystis aeruginosa from freshwater to estuaries has been described worldwide and salinity is reported as the main factor controlling the expansion of M. aeruginosa to coastal environments. Analyzing the expression levels of targeted genes and employing both targeted and non-targeted metabolomic approaches, this study investigated the effect of a sudden salt increase on the physiological and metabolic responses of two toxic M. aeruginosa strains separately isolated from fresh and brackish waters, respectively, PCC 7820 and 7806. Supported by differences in gene expressions and metabolic profiles, salt tolerance was found to be strain specific. An increase in salinity decreased the growth of M. aeruginosa with a lesser impact on the brackish strain. The production of intracellular microcystin variants in response to salt stress correlated well to the growth rate for both strains. Furthermore, the release of microcystins into the surrounding medium only occurred at the highest salinity treatment when cell lysis occurred. This study suggests that the physiological responses of M. aeruginosa involve the accumulation of common metabolites but that the intraspecific salt tolerance is based on the accumulation of specific metabolites. While one of these was determined to be sucrose, many others remain to be identified. Taken together, these results provide evidence that M. aeruginosa is relatively salt tolerant in the mesohaline zone and microcystin (MC) release only occurs when the capacity of the cells to deal with salt increase is exceeded. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1130 KW - Microcystis aeruginosa KW - microcystin KW - salt stress KW - metabolomic KW - transcript Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-472405 SN - 1866-8372 IS - 1130 ER - TY - JOUR A1 - des Aulnois, Maxime Georges A1 - Réveillon, Damien A1 - Robert, Elise A1 - Caruana, Amandine A1 - Briand, Enora A1 - Guljamow, Arthur A1 - Dittmann, Elke A1 - Amzil, Zouher A1 - Bormans, Myriam T1 - Salt shock responses of Microcystis revealed through physiological, transcript, and metabolomic analyses JF - Toxins N2 - The transfer of Microcystis aeruginosa from freshwater to estuaries has been described worldwide and salinity is reported as the main factor controlling the expansion of M. aeruginosa to coastal environments. Analyzing the expression levels of targeted genes and employing both targeted and non-targeted metabolomic approaches, this study investigated the effect of a sudden salt increase on the physiological and metabolic responses of two toxic M. aeruginosa strains separately isolated from fresh and brackish waters, respectively, PCC 7820 and 7806. Supported by differences in gene expressions and metabolic profiles, salt tolerance was found to be strain specific. An increase in salinity decreased the growth of M. aeruginosa with a lesser impact on the brackish strain. The production of intracellular microcystin variants in response to salt stress correlated well to the growth rate for both strains. Furthermore, the release of microcystins into the surrounding medium only occurred at the highest salinity treatment when cell lysis occurred. This study suggests that the physiological responses of M. aeruginosa involve the accumulation of common metabolites but that the intraspecific salt tolerance is based on the accumulation of specific metabolites. While one of these was determined to be sucrose, many others remain to be identified. Taken together, these results provide evidence that M. aeruginosa is relatively salt tolerant in the mesohaline zone and microcystin (MC) release only occurs when the capacity of the cells to deal with salt increase is exceeded. KW - Microcystis aeruginosa KW - microcystin KW - salt stress KW - metabolomic KW - transcript Y1 - 2020 U6 - https://doi.org/10.3390/toxins12030192 SN - 2072-6651 VL - 12 IS - 3 PB - MDPI CY - Basel ER - TY - JOUR A1 - Leunert, Franziska A1 - Eckert, Werner A1 - Paul, Andrea A1 - Gerhardt, Volkmar A1 - Grossart, Hans-Peter T1 - Phytoplankton response to UV-generated hydrogen peroxide from natural organic matter JF - Journal of plankton research N2 - In aquatic systems, natural organic matter (NOM) and in particular humic substances effectively absorb the ultraviolet (UV)/visible light spectrum of solar radiation and act as a photoprotective filter for organisms. Simultaneously, UV contributes to the generation of potentially harmful reactive oxygen species (ROS). Dose-response experiments were conducted on cyanobacteria and green algae with hydrogen peroxide (H2O2) as a long-lived representative of ROS. Delayed fluorescence (DF) decay kinetics was used as a non-invasive tool to follow changes of phytoplankton activity in real time. In order to investigate phototoxicity and photoprotection by NOM on phytoplankton, we exposed algae to UV-pre-irradiated NOM and direct UV excitation. Cyanobacteria responded to H2O2 concentrations as low as 10(-7) M, while green algae were 2 orders of magnitude less sensitive. UV irradiation of medium with NOM generated H2O2 concentrations of 1.5 x 10(-7) to 3.6 x 10(-7) M. When exposed to these concentrations, only the DF of cyanobacteria led to a measurable effect while that of green algae did not change. The addition of NOM protected all phytoplankton from direct UV irradiation, but cyanobacteria benefitted less. From this we conclude that UV-irradiated water enriched with NOM can adversely affect the physiology of cyanobacteria, but not of green algae, which might control phytoplankton composition and species-specific activities. KW - reactive oxygen species KW - Microcystis aeruginosa KW - green algae KW - delayed fluorescence KW - phycocyanin Y1 - 2014 U6 - https://doi.org/10.1093/plankt/fbt096 SN - 0142-7873 SN - 1464-3774 VL - 36 IS - 1 SP - 185 EP - 197 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Svanys, Algirdas A1 - Eigemann, Falk A1 - Großart, Hans-Peter A1 - Hilt, Sabine T1 - Microcystins do not necessarily lower the sensitivity of Microcystis aeruginosa to tannic acid JF - FEMS microbiology letters N2 - Different phytoplankton strains have been shown to possess varying sensitivities towards macrophyte allelochemicals, yet the reasons for this are largely unknown. To test whether microcystin (MC) is responsible for strain-specific sensitivities of Microcystis aeruginosa to macrophyte allelochemicals, we compared the sensitivity of 12 MC- and non-MC-producing M. aeruginosa strains, including an MC-deficient mutant and its wild type, to the polyphenolic allelochemical tannic acid (TA). Non-MC-producing strains showed a significantly higher sensitivity to TA than MC-producing strains, both in Chlorophyll a concentrations and quantum yields of photosystem II. In contrast, an MC-deficient mutant displayed a higher fitness against TA compared to its wild type. These results suggest that the resistance of M. aeruginosa to polyphenolic allelochemicals is not primarily related to MCs per se, but to other yet unknown protective mechanisms related to MCs. KW - allelopathy KW - Delta mcyB mutant KW - microcystin KW - Microcystis aeruginosa KW - tannic acid Y1 - 2016 U6 - https://doi.org/10.1093/femsle/fnv227 SN - 0378-1097 SN - 1574-6968 VL - 363 SP - 53 EP - 77 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Schuurmans, Jasper Merijn A1 - Brinkmann, Bregje W. A1 - Makower, Katharina A1 - Dittmann, Elke A1 - Huisman, Jef A1 - Matthijs, Hans C. P. T1 - Microcystin interferes with defense against high oxidative stress in harmful cyanobacteria JF - Harmful algae N2 - Harmful cyanobacteria producing toxic microcystins are a major concern in water quality management. In recent years, hydrogen peroxide (H2O2) has been successfully applied to suppress cyanobacterial blooms in lakes. Physiological studies, however, indicate that microcystin protects cyanobacteria against oxidative stress, suggesting that H2O2 addition might provide a selective advantage for microcystin-producing (toxic) strains. This study compares the response of a toxic Microcystis strain, its non-toxic mutant, and a naturally non-toxic Microcystis strain to H2O2 addition representative of lake treatments. All three strains initially ceased growth upon H2O2 addition. Contrary to expectation, the non-toxic strain and non-toxic mutant rapidly degraded the added H2O2 and subsequently recovered, whereas the toxic strain did not degrade H2O2 and did not recover. Experimental catalase addition enabled recovery of the toxic strain, demonstrating that rapid H2O2 degradation is indeed essential for cyanobacterial survival. Interestingly, prior to H2O2 addition, gene expression of a thioredoxin and peroxiredoxin was much lower in the toxic strain than in its non-toxic mutant. Thioredoxin and peroxiredoxin are both involved in H2O2 degradation, and microcystin may potentially suppress their activity. These results show that microcystin-producing strains are less prepared for high levels of oxidative stress, and are therefore hit harder by H2O2 addition than non-toxic strains. KW - Cyanobacteria KW - Harmful algal blooms KW - Microcystins KW - Hydrogen peroxide KW - Microarrays KW - Microcystis aeruginosa Y1 - 2018 U6 - https://doi.org/10.1016/j.hal.2018.07.008 SN - 1568-9883 SN - 1878-1470 VL - 78 SP - 47 EP - 55 PB - Elsevier CY - Amsterdam ER -