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 - 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 - JOUR A1 - Hu, Chenlin A1 - Ludsin, Stuart A. A1 - Martin, Jay F. A1 - Dittmann, Elke A1 - Lee, Jiyoung T1 - Mycosporine-like amino acids (MAAs)-producing Microcystis in Lake Erie BT - Development of a qPCR assay and insight into its ecology JF - Harmful algae N2 - Mycosporine-like amino acids (MAAs) are UV-absorbing metabolites found in cyanobacteria. While their protective role from UV in Microcystis has been studied in a laboratory setting, a full understanding of the ecology of MAA-producing versus non-MAA-producing Microcystis in natural environments is lacking. This study presents a new tool for quantifying MAA-producing Microcystis and applies it to obtain insight into the dynamics of MAA-producing and non-MAA-producing Microcystis in Lake Erie. This study first developed a sensitive, specific TaqMan real-time PCR assay that targets MAA synthetase gene C (mysC) of Microcystis (quantitative range: 1.7 × 101 to 1.7 × 107 copies/assay). Using this assay, Microcystis was quantified with a MAA-producing genotype (mysC+) in water samples (n = 96) collected during March-November 2013 from 21 Lake Erie sites (undetectable − 8.4 × 106 copies/ml). The mysC+ genotype comprised 0.3–37.8% of the Microcystis population in Lake Erie during the study period. The proportion of the mysC+ genotype during high solar UV irradiation periods (mean = 18.8%) was significantly higher than that during lower UV periods (mean = 9.7%). Among the MAAs, shinorine (major) and porphyra (minor) were detected with HPLC-PDA-MS/MS from the Microcystis isolates and water samples. However, no significant difference in the MAA concentrations existed between higher and lower solar UV periods when the MAA concentrations were normalized with Microcystis mysC abundance. Collectively, this study’s findings suggest that the MAA-producing Microcystis are present in Lake Erie, and they may be ecologically advantageous under high UV conditions, but not to the point that they exclusively predominate over the non-MAA-producers. KW - Shinorine KW - Porphyra KW - UV irradiation KW - Sunscreen KW - Eutrophication KW - Harmful algal bloom Y1 - 2018 U6 - https://doi.org/10.1016/j.hal.2018.05.010 SN - 1568-9883 SN - 1878-1470 VL - 77 SP - 1 EP - 10 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Barchewitz, Tino A1 - Guljamow, Arthur A1 - Meißner, Sven A1 - Timm, Stefan A1 - Henneberg, Manja A1 - Baumann, Otto A1 - Hagemann, Martin A1 - Dittmann, Elke T1 - Non-canonical localization of RubisCO under high-light conditions in the toxic cyanobacterium Microcystis aeruginosa PCC7806 JF - Environmental microbiology N2 - The frequent production of the hepatotoxin microcystin (MC) and its impact on the lifestyle of bloom-forming cyanobacteria are poorly understood. Here, we report that MC interferes with the assembly and the subcellular localization of RubisCO, in Microcystis aeruginosa PCC7806. Immunofluorescence, electron microscopic and cellular fractionation studies revealed a pronounced heterogeneity in the subcellular localization of RubisCO. At high cell density, RubisCO particles are largely separate from carboxysomes in M. aeruginosa and relocate to the cytoplasmic membrane under high-light conditions. We hypothesize that the binding of MC to RubisCO promotes its membrane association and enables an extreme versatility of the enzyme. Steady-state levels of the RubisCO CO2 fixation product 3-phosphoglycerate are significantly higher in the MC-producing wild type. We also detected noticeable amounts of the RubisCO oxygenase reaction product secreted into the medium that may support the mutual interaction of M. aeruginosa with its heterotrophic microbial community. Y1 - 2019 U6 - https://doi.org/10.1111/1462-2920.14837 SN - 1462-2912 SN - 1462-2920 VL - 21 IS - 12 SP - 4836 EP - 4851 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Pancrace, Claire A1 - Ishida, Keishi A1 - Briand, Enora A1 - Pichi, Douglas Gatte A1 - Weiz, Annika R. A1 - Guljarmow, Arthur A1 - Scalvenzi, Thibault A1 - Sassoon, Nathalie A1 - Hertweck, Christian A1 - Dittmann, Elke A1 - Gugger, Muriel T1 - Unique Biosynthetic Pathway in Bloom-Forming Cyanobacterial Genus Microcystis Jointly Assembles Cytotoxic Aeruginoguanidines and Microguanidines JF - ACS chemical biology N2 - The cyanobacterial genus Microcystis is known to produce an elaborate array of structurally unique and biologically active natural products, including hazardous cyanotoxins. Cytotoxic aeruginoguanidines represent a yet unexplored family of peptides featuring a trisubstituted benzene unit and farnesylated arginine derivatives. In this study, we aimed at assigning these compounds to a biosynthetic gene cluster by utilizing biosynthetic attributes deduced from public genomes of Microcystis and the sporadic distribution of the metabolite in axenic strains of the Pasteur Culture Collection of Cyanobacteria. By integrating genome mining with untargeted metabolomics using liquid chromatography with mass spectrometry, we linked aeruginoguanidine (AGD) to a nonribosomal peptide synthetase gene cluster and coassigned a significantly smaller product to this pathway, microguanidine (MGD), previously only reported from two Microcystis blooms. Further, a new intermediate class of compounds named microguanidine amides was uncovered, thereby further enlarging this compound family. The comparison of structurally divergent AGDs and MGDs reveals an outstanding versatility of this biosynthetic pathway and provides insights into the assembly of the two compound subfamilies. Strikingly, aeruginoguanidines and microguanidines were found to be as widespread as the hepatotoxic microcystins, but the occurrence of both toxin families appeared to be mutually exclusive. Y1 - 2018 U6 - https://doi.org/10.1021/acschembio.8b00918 SN - 1554-8929 SN - 1554-8937 VL - 14 IS - 1 SP - 67 EP - 75 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Liaimer, Anton A1 - Jensen, John B. A1 - Dittmann, Elke T1 - A Genetic and Chemical Perspective on Symbiotic Recruitment of Cyanobacteria of the Genus Nostoc into the Host Plant Blasia pusilla L. JF - Frontiers in microbiology N2 - Liverwort Blasia pusilla L. recruits soil nitrogen-fixing cyanobacteria of genus Nostoc as symbiotic partners. In this work we compared Nostoc community composition inside the plants and in the soil around them from two distant locations in Northern Norway. STRR fingerprinting and 16S rDNA phylogeny reconstruction showed a remarkable local diversity among isolates assigned to several Nostoc clades. An extensive web of negative allelopathic interactions was recorded at an agricultural site, but not at the undisturbed natural site. The cell extracts of the cyanobacteria did not show antimicrobial activities, but four isolates were shown to be cytotoxic to human cells. The secondary metabolite profiles of the isolates were mapped by MALDI-TOF MS, and the most prominent ions were further analyzed by Q-TOF for MS/MS aided identification. Symbiotic isolates produced a great variety of small peptide-like substances, most of which lack any record in the databases. Among identified compounds we found microcystin and nodularin variants toxic to eukaryotic cells. Microcystin producing chemotypes were dominating as symbiotic recruits but not in the free-living community. In addition, we were able to identify several novel aeruginosins and banyaside-like compounds, as well as nostocyclopeptides and nosperin. KW - Cyanobacteria KW - secondary metabolites KW - symbiosis KW - Blasia KW - Nostoc KW - allelopathy Y1 - 2016 U6 - https://doi.org/10.3389/fmicb.2016.01693 SN - 1664-302X VL - 7 SP - 449 EP - 474 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Reyna-González, Emmanuel A1 - Schmid, Bianca A1 - Petras, Daniel A1 - Süssmuth, Roderich D. A1 - Dittmann, Elke T1 - Leader Peptide-Free In Vitro Reconstitution of Microviridin Biosynthesis Enables Design of Synthetic Protease-Targeted Libraries JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - Microviridins are a family of ribosomally synthesized and post-translationally modified peptides with a highly unusual architecture featuring non-canonical lactone as well as lactam rings. Individual variants specifically inhibit different types of serine proteases. Here we have established an efficient in vitro reconstitution approach based on two ATP-grasp ligases that were constitutively activated using covalently attached leader peptides and a GNAT-type N-acetyltransferase. The method facilitates the efficient in vitro one-pot transformation of microviridin core peptides to mature microviridins. The engineering potential of the chemo-enzymatic technology was demonstrated for two synthetic peptide libraries that were used to screen and optimize microviridin variants targeting the serine proteases trypsin and subtilisin. Successive analysis of intermediates revealed distinct structure-activity relationships for respective target proteases. KW - biosynthesis KW - cyanobacteria KW - microviridins KW - natural products KW - peptides Y1 - 2016 U6 - https://doi.org/10.1002/anie.201604345 SN - 1433-7851 SN - 1521-3773 VL - 55 SP - 9398 EP - 9401 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Pearson, Leanne A. A1 - Dittmann, Elke A1 - Mazmouz, Rabia A1 - Ongley, Sarah E. A1 - Neilan, Brett A. T1 - The genetics, biosynthesis and regulation of toxic specialized metabolites of cyanobacteria JF - Harmful algae N2 - The production of toxic metabolites by cyanobacterial blooms represents a significant threat to the health of humans and ecosystems worldwide. Here we summarize the current state of the knowledge regarding the genetics, biosynthesis and regulation of well-characterized cyanotoxins, including the microcystins, nodularin, cylindrospermopsin, saxitoxins and antitoxins, as well as the lesser-known marine toxins (e.g. lyngbyatoxin, aplysiatoxin, jamaicamides, barbamide, curacin, hectochlorin and apratoxins). (C) 2015 Elsevier B.V. All rights reserved. KW - Cyanobacteria KW - Cyanotoxins KW - Specialized metabolites KW - Genetics KW - Biosynthesis KW - Regulation Y1 - 2016 U6 - https://doi.org/10.1016/j.hal.2015.11.002 SN - 1568-9883 SN - 1878-1470 VL - 54 SP - 98 EP - 111 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ahmed, Muhammad N. A1 - Reyna-Gonzalez, Emmanuel A1 - Schmid, Bianca A1 - Wiebach, Vincent A1 - Suessmuth, Roderich D. A1 - Dittmann, Elke A1 - Fewer, David P. T1 - Phylogenomic Analysis of the Microviridin Biosynthetic Pathway Coupled with Targeted Chemo-Enzymatic Synthesis Yields Potent Protease Inhibitors JF - ACS chemical biology N2 - Natural products and their semisynthetic derivatives are an important source of drugs for the pharmaceutical industry. Bacteria are prolific producers of natural products and encode a vast diversity of natural product biosynthetic gene clusters. However, much of this diversity is inaccessible to natural product discovery. Here, we use a combination of phylogenomic analysis of the microviridin biosynthetic pathway and chemo-enzymatic synthesis of bioinformatically predicted microviridins to yield new protease inhibitors. Phylogenomic analysis demonstrated that microviridin biosynthetic gene clusters occur across the bacterial domain and encode three distinct subtypes of precursor peptides. Our analysis shed light on the evolution of microviridin biosynthesis and enabled prioritization of their chemo-enzymatic production. Targeted one-pot synthesis of four microviridins encoded by the cyanobacterium Cyanothece sp. PCC 7822 identified a set of novel and potent serine protease inhibitors, the most active of which had an IC50 value of 21.5 nM. This study advances the genome mining techniques available for natural product discovery and obviates the need to culture bacteria. Y1 - 2017 U6 - https://doi.org/10.1021/acschembio.7b00124 SN - 1554-8929 SN - 1554-8937 VL - 12 SP - 1538 EP - 1546 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Meyer, Sabine A1 - Mainz, Andi A1 - Kehr, Jan-Christoph A1 - Suessmuth, Roderich A1 - Dittmann, Elke T1 - Prerequisites of Isopeptide Bond Formation in Microcystin Biosynthesis JF - ChemBioChem : a European journal of chemical biology N2 - The biosynthesis of the potent cyanobacterial hepatotoxin microcystin involves isopeptide bond formation through the carboxylic acid side chains of d-glutamate and -methyl d-aspartate. Analysis of the in vitro activation profiles of the two corresponding adenylation domains, McyE-A and McyB-A(2), either in a didomain or a tridomain context with the cognate thiolation domain and the upstream condensation domain revealed that substrate activation of both domains strictly depended on the presence of the condensation domains. We further identified two key amino acids in the binding pockets of both adenylation domains that could serve as a bioinformatic signature of isopeptide bond-forming modules incorporating d-glutamate or d-aspartate. Our findings further contribute to the understanding of the multifaceted role of condensation domains in nonribosomal peptide synthetase assembly lines. KW - amino acids KW - biosynthesis KW - cyanobacteria KW - nonribosomal peptide KW - substrate specificity Y1 - 2017 U6 - https://doi.org/10.1002/cbic.201700389 SN - 1439-4227 SN - 1439-7633 VL - 18 SP - 2376 EP - 2379 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Guljamow, Arthur A1 - Barchewitz, Tino A1 - Große, Rebecca A1 - Timm, Stefan A1 - Hagemann, Martin A1 - Dittmann, Elke T1 - Diel Variations of Extracellular Microcystin Influence the Subcellular Dynamics of RubisCO in Microcystis aeruginosa PCC 7806 JF - Microorganisms : open access journal N2 - The ubiquitous freshwater cyanobacterium Microcystis is remarkably successful, showing a high tolerance against fluctuations in environmental conditions. It frequently forms dense blooms which can accumulate significant amounts of the hepatotoxin microcystin, which plays an extracellular role as an infochemical but also acts intracellularly by interacting with proteins of the carbon metabolism, notably with the CO2 fixing enzyme RubisCO. Here we demonstrate a direct link between external microcystin and its intracellular targets. Monitoring liquid cultures of Microcystis in a diel experiment revealed fluctuations in the extracellular microcystin content that correlate with an increase in the binding of microcystin to intracellular proteins. Concomitantly, reversible relocation of RubisCO from the cytoplasm to the cell’s periphery was observed. These variations in RubisCO localization were especially pronounced with cultures grown at higher cell densities. We replicated these effects by adding microcystin externally to cultures grown under continuous light. Thus, we propose that microcystin may be part of a fast response to conditions of high light and low carbon that contribute to the metabolic flexibility and the success of Microcystis in the field. KW - cyanobacterial bloom KW - Microcystis KW - microcystin KW - RubisCO KW - extracellular signaling Y1 - 2021 U6 - https://doi.org/10.3390/microorganisms9061265 SN - 2076-2607 VL - 9 IS - 6 PB - MDPI CY - Basel ER - TY - GEN A1 - Guljamow, Arthur A1 - Barchewitz, Tino A1 - Große, Rebecca A1 - Timm, Stefan A1 - Hagemann, Martin A1 - Dittmann, Elke T1 - Diel Variations of Extracellular Microcystin Influence the Subcellular Dynamics of RubisCO in Microcystis aeruginosa PCC 7806 T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The ubiquitous freshwater cyanobacterium Microcystis is remarkably successful, showing a high tolerance against fluctuations in environmental conditions. It frequently forms dense blooms which can accumulate significant amounts of the hepatotoxin microcystin, which plays an extracellular role as an infochemical but also acts intracellularly by interacting with proteins of the carbon metabolism, notably with the CO2 fixing enzyme RubisCO. Here we demonstrate a direct link between external microcystin and its intracellular targets. Monitoring liquid cultures of Microcystis in a diel experiment revealed fluctuations in the extracellular microcystin content that correlate with an increase in the binding of microcystin to intracellular proteins. Concomitantly, reversible relocation of RubisCO from the cytoplasm to the cell’s periphery was observed. These variations in RubisCO localization were especially pronounced with cultures grown at higher cell densities. We replicated these effects by adding microcystin externally to cultures grown under continuous light. Thus, we propose that microcystin may be part of a fast response to conditions of high light and low carbon that contribute to the metabolic flexibility and the success of Microcystis in the field. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1154 KW - cyanobacterial bloom KW - Microcystis KW - microcystin KW - RubisCO KW - extracellular signaling Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-521287 SN - 1866-8372 IS - 1154 ER - TY - JOUR A1 - Köker, Latife A1 - Akçaalan, Reyhan A1 - Dittmann, Elke A1 - Albay, Meriç T1 - Depth profiles of protein-bound microcystin in Küçükçekmece Lagoon JF - Toxicon : an international journal devoted to the exchange of knowledge on the poisons derived from the tissues of plants and animals ; official journal of the International Society on Toxinology N2 - Microcystis is the most commonly found toxic cyanobacterial genus around the world and has a negative impact on the ecosystem. As a predominant producer of the potent hepatotoxin microcystin (MC), the genus causes outbreaks in freshwaters worldwide. Standard analytical methods that are used for the detection of microcystin variants can only measure the free form of microcystin in cells. Since microcystin was found as free and proteinbound forms in the cells, a significant proportion of microcystin is underestimated with analytical methods. The aim of the study was to measure protein-bound microcystins and determine the environmental factors that affect the binding of microcystin to proteins. Samples were taken at depths of surface, 1 m, 5 m, 10 m, 15 m, and 18 m in Kucukcekmece Lagoon to analyze depth profiles of two different microcystin forms from June to September 2012 at regular monthly intervals. Our findings suggest that the most important parameter affecting proteinbound microcystin at surface water is high light. Due to favorable environmental conditions such as temperature, light, and physicochemical parameters, the higher microcystin contents, both free and protein-bound MCs, were found in summer periods. KW - Microcystis KW - Microcystin KW - Protein-bound microcystin KW - Mcy gene KW - Kucukcekmece Lagoon Y1 - 2021 U6 - https://doi.org/10.1016/j.toxicon.2021.05.005 SN - 0041-0101 SN - 1879-3150 VL - 198 SP - 156 EP - 163 PB - Elsevier CY - Oxford 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 - Soeriyadi, Angela H. A1 - Ongley, Sarah E. A1 - Kehr, Jan-Christoph A1 - Pickford, Russel A1 - Dittmann, Elke A1 - Neilan, Brett A. T1 - Tailoring enzyme stringency masks the multispecificity of a lyngbyatoxin (indolactam alkaloid) nonribosomal peptide synthetase JF - ChemBioChem N2 - Indolactam alkaloids are activators of protein kinase C (PKC) and are of pharmacological interest for the treatment of pathologies involving PKC dysregulation. The marine cyanobacterial nonribosomal peptide synthetase (NRPS) pathway for lyngbyatoxin biosynthesis, which we previously expressed in E. coli, was studied for its amenability towards the biosynthesis of indolactam variants. Modification of culture conditions for our E. coli heterologous expression host and analysis of pathway products suggested the native lyngbyatoxin pathway NRPS does possess a degree of relaxed specificity. Site-directed mutagenesis of two positions within the adenylation domain (A-domain) substrate-binding pocket was performed, resulting in an alteration of substrate preference between valine, isoleucine, and leucine. We observed relative congruence of in vitro substrate activation by the LtxA NRPS to in vivo product formation. While there was a preference for isoleucine over leucine, the substitution of alternative tailoring domains may unveil the true in vivo effects of the mutations introduced herein. KW - a domain KW - indolactams KW - MbtH KW - natural products KW - teleocidin Y1 - 2021 U6 - https://doi.org/10.1002/cbic.202100574 SN - 1439-4227 SN - 1439-7633 VL - 23 IS - 3 PB - Wiley-VCH CY - Weinheim 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 - Krumbholz, Julia A1 - Ishida, Keishi A1 - Baunach, Martin A1 - Teikari, Jonna A1 - Rose, Magdalena M. A1 - Sasso, Severin A1 - Hertweck, Christian A1 - Dittmann, Elke T1 - Deciphering chemical mediators regulating specialized metabolism in a symbiotic cyanobacterium JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker. International edition N2 - Genomes of cyanobacteria feature a variety of cryptic biosynthetic pathways for complex natural products, but the peculiarities limiting the discovery and exploitation of the metabolic dark matter are not well understood. Here we describe the discovery of two cell density-dependent chemical mediators, nostoclide and nostovalerolactone, in the symbiotic model strain Nostoc punctiforme, and demonstrate their pronounced impact on the regulation of specialized metabolism. Through transcriptional, bioinformatic and labeling studies we assigned two adjacent biosynthetic gene clusters to the biosynthesis of the two polyketide mediators. Our findings provide insight into the orchestration of specialized metabolite production and give lessons for the genomic mining and high-titer production of cyanobacterial bioactive compounds. KW - Biosynthesis KW - Cyanobacteria KW - Genomic Mining KW - Quorum Sensing KW - Specialized KW - Metabolism Y1 - 2022 U6 - https://doi.org/10.1002/anie.202204545 SN - 1433-7851 SN - 1521-3773 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Nwosu, Ebuka Canisius A1 - Roeser, Patricia Angelika A1 - Yang, Sizhong A1 - Pinkerneil, Sylvia A1 - Ganzert, Lars A1 - Dittmann, Elke A1 - Brauer, Achim A1 - Wagner, Dirk A1 - Liebner, Susanne T1 - Species-level spatio-temporal dynamics of cyanobacteria in a hard-water temperate lake in the Southern Baltics JF - Frontiers in microbiology N2 - Cyanobacteria are important primary producers in temperate freshwater ecosystems. However, studies on the seasonal and spatial distribution of cyanobacteria in deep lakes based on high-throughput DNA sequencing are still rare. In this study, we combined monthly water sampling and monitoring in 2019, amplicon sequence variants analysis (ASVs; a proxy for different species) and quantitative PCR targeting overall cyanobacteria abundance to describe the seasonal and spatial dynamics of cyanobacteria in the deep hard-water oligo-mesotrophic Lake Tiefer See, NE Germany. We observed significant seasonal variation in the cyanobacterial community composition (p < 0.05) in the epi- and metalimnion layers, but not in the hypolimnion. In winter-when the water column is mixed-picocyanobacteria (Synechococcus and Cyanobium) were dominant. With the onset of stratification in late spring, we observed potential niche specialization and coexistence among the cyanobacteria taxa driven mainly by light and nutrient dynamics. Specifically, ASVs assigned to picocyanobacteria and the genus Planktothrix were the main contributors to the formation of deep chlorophyll maxima along a light gradient. While Synechococcus and different Cyanobium ASVs were abundant in the epilimnion up to the base of the euphotic zone from spring to fall, Planktothrix mainly occurred in the metalimnetic layer below the euphotic zone where also overall cyanobacteria abundance was highest in summer. Our data revealed two potentially psychrotolerant (cold-adapted) Cyanobium species that appear to cope well under conditions of lower hypolimnetic water temperature and light as well as increasing sediment-released phosphate in the deeper waters in summer. The potential cold-adapted Cyanobium species were also dominant throughout the water column in fall and winter. Furthermore, Snowella and Microcystis-related ASVs were abundant in the water column during the onset of fall turnover. Altogether, these findings suggest previously unascertained and considerable spatiotemporal changes in the community of cyanobacteria on the species level especially within the genus Cyanobium in deep hard-water temperate lakes. KW - Cyanobium KW - picocyanobacteria diversity KW - amplicon sequencing KW - lake monitoring KW - ecological succession KW - lake stratification KW - psychrotolerant Y1 - 2021 U6 - https://doi.org/10.3389/fmicb.2021.761259 SN - 1664-302X VL - 12 PB - Frontiers Media CY - Lausanne ER -