The Experts below are selected from a list of 2685 Experts worldwide ranked by ideXlab platform
Rainer Kurmayer - One of the best experts on this subject based on the ideXlab platform.
-
Genetic identification of microcystin ecotypes in toxic cyanobacteria of the genus Planktothrix.
Microbiology (Reading England), 2020Co-Authors: Rainer Kurmayer, Guntram Christiansen, Marlies Gumpenberger, Jutta FastnerAbstract:Microcystins (MCs) are toxic heptapeptides which are synthesized by the filamentous cyanobacterium Planktothrix and other genera via non-ribosomal peptide synthesis. MCs share the common structure cyclo(-D-ala1-L-X2-D-erythro-beta-iso-aspartic acid3-L-Z4-adda5-D-Glu6-N-methyl-dehydroalanine7) [Adda; (2S, 3S, 8S, 9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid], in which numerous MC variants have been reported. In general, the variation in structure is due to different amino acid residues in positions 7, 2 and 4 within the MC molecule, which are thought to be activated by the adenylation domains mcyAAd1, mcyBAd1 and mcyCAd, respectively. It was the aim of the study (i) to identify MC ecotypes that differed in the production of specific MC variants and (ii) to correlate the genetic variation within adenylation domains with the observed MC variants among 17 Planktothrix strains. Comparison of the sequences of mcyAAd1 revealed two distinctive Ad-genotypes differing in base pair composition and the insertion of an N-methyl transferase (NMT) domain. The mcyAAd1 genotype with NMT (2854 bp) correlated with N-methyl-dehydroalanine and the mcyAAd1 genotype without NMT (1692 bp) correlated with dehydrobutyrine in position 7. Within mcyBAd1, a lower genetic variation (0-4 %) and an exclusive correlation between one Ad-genotype and homotyrosine as well as another Ad-genotype and arginine in position 2 was found. The sequences of mcyCAd were found to be highly similar (0-1 % dissimilarity) and all strains contained arginine in position 4. The results on adenylation domain polymorphism do provide insights into the evolutionary origin of adenylation domains in Planktothrix and may be combined with ecological research in order to provide clues about the abundance of genetically defined MC ecotypes in nature.
-
role of toxic and bioactive secondary metabolites in colonization and bloom formation by filamentous cyanobacteria Planktothrix
Harmful Algae, 2016Co-Authors: Rainer Kurmayer, Li Deng, Elisabeth EntfellnerAbstract:Bloom-forming cyanobacteria Planktothrix agardhii and P. rubescens are regularly involved in the occurrence of cyanotoxin in lakes and reservoirs. Besides microcystins (MCs), which inhibit eukaryotic protein phosphatase 1 and 2A, several families of bioactive peptides are produced, thereby resulting in impressive secondary metabolite structural diversity. This review will focus on the current knowledge of the phylogeny, morphology, and ecophysiological adaptations of Planktothrix as well as the toxins and bioactive peptides produced. The relatively well studied ecophysiological adaptations (buoyancy, shade tolerance, nutrient storage capacity) can partly explain the invasiveness of this group of cyanobacteria that bloom within short periods (weeks to months). The more recent elucidation of the genetic basis of toxin and bioactive peptide synthesis paved the way for investigating its regulation both in the laboratory using cell cultures as well as under field conditions. The high frequency of several toxin and bioactive peptide synthesis genes observed within P. agardhii and P. rubescens, but not for other Planktothrix species (e.g. P. pseudagardhii), suggests a potential functional linkage between bioactive peptide production and the colonization potential and possible dominance in habitats. It is hypothesized that, through toxin and bioactive peptide production, Planktothrix act as a niche constructor at the ecosystem scale, possibly resulting in an even higher ability to monopolize resources, positive feedback loops, and resilience under stable environmental conditions. Thus, refocusing harmful algal bloom management by integrating ecological and phylogenetic factors acting on toxin and bioactive peptide synthesis gene distribution and concentrations could increase the predictability of the risks originating from Planktothrix blooms.
-
Emergence of nontoxic mutants as revealed by single filament analysis in bloom-forming cyanobacteria of the genus Planktothrix
BMC Microbiology, 2016Co-Authors: Qin Chen, Guntram Christiansen, Li Deng, Rainer KurmayerAbstract:BackgroundBloom-forming cyanobacteria cause toxic algae outbreaks in lakes and reservoirs. We aimed to explore and quantify mutation events occurring within the large mcy gene cluster (55 kbp) encoding microcystin (MC) biosynthesis that inactivate MC net production. For this purpose we developed a workflow to detect mutations in situ occurring anywhere within the large mcy gene cluster as amplified from one single filament of the red-pigmented cyanobacterium Planktothrix rubescens. From five lakes of the Alps eight hundred Planktothrix filaments were isolated and each individual filament was analyzed for mutations affecting the mcy genes.ResultsMutations inactivating MC synthesis were either through an insertion element ISPlr1 or the partial deletion of mcy genes. Neutral mutations not affecting MC biosynthesis occurred within two intergenic spacer regions, either through the insertion of a Holliday-junction resolvase RusA or ISPlr1. Altogether, the insertions affected a few mcy genes only and their location was correlated with regions similar to repetitive extragenic palindromic DNA sequences (REPs). Taking all of the filaments together, the mutations leading to the inactivation of MC synthesis were more rare (0.5–6.9 %), when compared with the neutral mutations (7.5–20.6 %). On a spatial-temporal scale the ratio of MC synthesis-inactivating vs. neutral mutations was variable, e.g., the filament abundance carrying partial deletion of mcyD (5.2–19.4 %) and/or mcyHA (0–7.3 %) exceeded the abundance of neutral mutations.ConclusionsIt is concluded that insertion events occurring within the Planktothrix mcy gene cluster are predictable due to their correlation with REPs. The frequency of occurrence of the REPs within the mcy gene cluster of Planktothrix relates to the rather common mutation of mcy genes in Planktothrix. Spatial-temporal variable conditions may favor the emergence of partial mcy deletion mutants in Planktothrix, in particular a higher proportion of genotypes resulting in inactivation of MC synthesis might be caused by increased ISPlr1 activity.
-
emergence of nontoxic mutants as revealed by single filament analysis in bloom forming cyanobacteria of the genus Planktothrix
BMC Microbiology, 2016Co-Authors: Qin Chen, Guntram Christiansen, Li Deng, Rainer KurmayerAbstract:Background Bloom-forming cyanobacteria cause toxic algae outbreaks in lakes and reservoirs. We aimed to explore and quantify mutation events occurring within the large mcy gene cluster (55 kbp) encoding microcystin (MC) biosynthesis that inactivate MC net production. For this purpose we developed a workflow to detect mutations in situ occurring anywhere within the large mcy gene cluster as amplified from one single filament of the red-pigmented cyanobacterium Planktothrix rubescens. From five lakes of the Alps eight hundred Planktothrix filaments were isolated and each individual filament was analyzed for mutations affecting the mcy genes.
-
the toxicity and enzyme activity of a chlorine and sulfate containing aeruginosin isolated from a non microcystin producing Planktothrix strain
Harmful Algae, 2014Co-Authors: Esther Kohler, Rainer Kurmayer, Verena Grundler, Daniel Haussinger, Karl Gademann, Jakob Pernthaler, Judith F BlomAbstract:Abstract The toxicity of six different Planktothrix strains was examined in acute toxicity assays with the crustacean Thamnocephalus platyurus . The presence of toxicity in two strains could be explained by the occurrence of microcystins. The other four Planktothrix strains were not able to produce microcystins due to different mutations in the microcystin synthetase ( mcy ) gene cluster. In these strains, toxicity was attributed to the presence of chlorine and sulfate containing compounds. The main representative, called aeruginosin 828A, of such a compound in the Planktothrix strain 91/1 was isolated, and structure elucidation by 2D NMR and MS methods revealed the presence of phenyllactic acid ( Pla ), chloroleucine ( Cleu ), 2-carboxy-6-(4′-sulfo-xylosyl)-octahydroindole ( Choi ), and 3-aminoethyl-1- N -amidino-Δ-3-pyrroline ( Aeap ) residues. Aeruginosin 828A was found to be toxic for T. platyurus with a LC 50 value of 22.4 μM, which is only slightly higher than the toxicity found for microcystins. Additionally, very potent inhibition values for thrombin (IC 50 = 21.8 nM) and for trypsin (IC 50 = 112 nM) have been determined for aeruginosin 828A. These data support the hypothesis that aeruginosins containing chlorine and sulfate groups, which were found in microcystin-deficient Planktothrix strains, can be considered as another class of toxins.
Thomas Rohrlack - One of the best experts on this subject based on the ideXlab platform.
-
the red queen race between parasitic chytrids and their host Planktothrix a test using a time series reconstructed from sediment dna
PLOS ONE, 2015Co-Authors: Marcia Kyle, Sigrid Haande, Veronika Ostermaier, Thomas RohrlackAbstract:Parasitic chytrid fungi (phylum Chytridiomycota) are known to infect specific phytoplankton, including the filamentous cyanobacterium Planktothrix. Subspecies, or chemotypes of Planktothrix can be identified by the presence of characteristic oligopeptides. Some of these oligopeptides can be associated with important health concerns due to their potential for toxin production. However, the relationship between chytrid parasite and Planktothrix host is not clearly understood and more research is needed. To test the parasite - host relationship over time, we used a sediment core extracted from a Norwegian lake known to contain both multiple Planktothrix chemotype hosts and their parasitic chytrid. Sediment DNA of chytrids and Planktothrix was amplified and a 35-year coexistence was found. It is important to understand how these two antagonistic species can coexistence in a lake. Reconstruction of the time series showed that between 1979–1990 at least 2 strains of Planktothrix were present and parasitic pressure exerted by chytrids was low. After this period one chemotype became dominant and yet showed continued low susceptibility to chytrid parasitism. Either environmental conditions or intrinsic characteristics of Planktothrix could have been responsible for this continued dominance. One possible explanation could be found in the shift of Planktothrix to the metalimnion, an environment that typically consists of low light and decreased temperatures. Planktothrix are capable of growth under these conditions while the chytrid parasites are constrained. Another potential explanation could be due to the differences between cellular oligopeptide variations found between Planktothrix chemotypes. These oligopeptides can function as defense systems against chytrids. Our findings suggest that chytrid driven diversity was not maintained over time, but that the combination of environmental constraints and multiple oligopeptide production to combat chytrids could have allowed one Planktothrix chemotype to have dominance despite chytrid presence.
-
Historical Planktothrix diversity across seven Norwegian lakes implies environmentally driven niche differentiation
Frontiers in Ecology and Evolution, 2015Co-Authors: Marcia Kyle, Sigrid Haande, Tom Andersen, Thomas RohrlackAbstract:Non-ribosomal synthetase-produced cyanopeptoline oligopeptides enables differentiation of subpopulations of the cyanobacterial genus Planktothrix into chemotypes. It is unknown what influences the population structuring of these chemotypes. Sediment cores from seven lakes in southern Norway allowed temporal reconstruction of chemotype diversity from sites where there is only fragmented historical information. Sediment DNA was amplified using primers designed to specify the chemotype variations found within the cyanopeptoline ociB gene cluster. Findings indicate that of the seven lakes studied, only two lakes had Planktothrix populations containing all four of the most common Norwegian chemotypes. We used Principle Component and Kendall tau analysis to investigate the ability of monitoring data to predict chemotype diversity, and to identify possible biotic or abiotic barriers to chemotype dispersal. The best predictor was a negative relationship between number of chemotypes present in a lake and the concentration of chlorophyll a in the top 0 – 4 meters. At low chlorophyll a concentrations, light penetration is typically deeper, which could allow light tolerant Planktothrix to move deeper into the colder waters. Recent research findings have suggested this allows for a window of opportunity for Planktothrix to escape parasitism. With this added cold, light-constrained niche, more chemotypes might find refuge. The resulting increase in chemotype diversity within Planktothrix populations could present a greater defense against parasitism when conditions varied, such as by seasonal light changes.
-
Amplification of DNA in sediment cores to detect historic Planktothrix occurrence in three Norwegian lakes
Journal of Paleolimnology, 2014Co-Authors: Marcia Kyle, Sigrid Haande, Jorn Henrik Sonstebo, Thomas RohrlackAbstract:The past 50 years have been marked by overabundance of cyanobacteria in many lakes. One cyanobacterium in particular, Planktothrix, produces large blooms that affect phytoplankton diversity and presents human health concerns. Historical information on Planktothrix, however, is limited. More background information on this taxon would be useful for water management. Archival DNA in lake sediment has shown increasing promise for providing insights into historical lake conditions. In an effort to identify Planktothrix DNA in sediments, we developed a set of primers to amplify the DNA, using sequences from the non-ribosomal peptide synthetase gene cluster, ociB, which codes for the oligopeptide class cyanopeptolin. Four primer sets were designed, using a single forward primer and four separate reverse primers that span a specific sequence fragment between 50 and 383 base pairs in length. This enabled us to assess the recovery of Planktothrix DNA in sediment cores from three lakes that differed with respect to watershed characteristics, sedimentation rate, chemistry and organic matter content. The method proved to be sensitive for detection of Planktothrix ociB in sediment from these lakes. Long fragments were found in sediment deposited over the last 20 years, whereas shorter DNA fragments were amplified from samples taken over the entire length of the cores. Highest DNA concentrations were found in the lake with highest levels of aluminum and magnesium in the sediment, suggestive of clay-rich deposits. The lake with the highest organic matter content and lowest sedimentation rate also had the lowest concentrations of Planktothrix DNA. In this organic-rich sediment, however, the shortest fragment primers amplified Planktothrix DNA from sediment deposited over the last 300 years. This research shows the potential for DNA in sediment archives to yield information about past cyanobacteria presence in a variety of lakes, and indicates that it is a useful tool for identifying the presence of Planktothrix, an important nuisance cyanobacterium in some lakes.
-
from green to red horizontal gene transfer of the phycoerythrin gene cluster between Planktothrix strains
Applied and Environmental Microbiology, 2013Co-Authors: Ave Toomingklunderud, Thomas Rohrlack, Hanne Sogge, Trine B Rounge, P K Hayes, Alexander J Nederbragt, Karin Lagesen, Gernot Glockner, Kjetill S JakobsenAbstract:Horizontal gene transfer is common in cyanobacteria, and transfer of large gene clusters may lead to acquisition of new functions and conceivably niche adaption. In the present study, we demonstrate that horizontal gene transfer between closely related Planktothrix strains can explain the production of the same oligopeptide isoforms by strains of different colors. Comparison of the genomes of eight Planktothrix strains revealed that strains producing the same oligopeptide isoforms are closely related, regardless of color. We have investigated genes involved in the synthesis of the photosynthetic pigments phycocyanin and phycoerythrin, which are responsible for green and red appearance, respectively. Sequence comparisons suggest the transfer of a functional phycoerythrin gene cluster generating a red phenotype in a strain that is otherwise more closely related to green strains. Our data show that the insertion of a DNA fragment containing the 19.7-kb phycoerythrin gene cluster has been facilitated by homologous recombination, also replacing a region of the phycocyanin operon. These findings demonstrate that large DNA fragments spanning entire functional gene clusters can be effectively transferred between closely related cyanobacterial strains and result in a changed phenotype. Further, the results shed new light on the discussion of the role of horizontal gene transfer in the sporadic distribution of large gene clusters in cyanobacteria, as well as the appearance of red and green strains.
-
putative antiparasite defensive system involving ribosomal and nonribosomal oligopeptides in cyanobacteria of the genus Planktothrix
Applied and Environmental Microbiology, 2013Co-Authors: Thomas Rohrlack, Guntram Christiansen, Rainer KurmayerAbstract:Parasitic chytrid fungi can inflict significant mortality on cyanobacteria but frequently fail to keep cyanobacterial dominance and bloom formation in check. Our study tested whether oligopeptide production, a common feature in many cyanobacteria, can be a defensive mechanism against chytrid parasitism. The study employed the cyanobacterial strain Planktothrix NIVA-CYA126/8 and its mutants with knockout mutations for microcystins, anabaenopeptins, and microviridins, major oligopeptide classes to be found in NIVA-CYA126/8. Four chytrid strains were used as parasite models. They are obligate parasites of Planktothrix and are unable to exploit alternative food sources. All chytrid strains were less virulent to the NIVA-CYA126/8 wild type than to at least one of its oligopeptide knockout mutants. One chytrid strain even failed to infect the wild type, while exhibiting considerable virulence to all mutants. It is therefore evident that producing microcystins, microviridins, and/or anabaenopeptins can reduce the virulence of chytrids to Planktothrix, thereby increasing the host's chance of survival. Microcystins and anabaenopeptins are nonribosomal oligopeptides, while microviridins are produced ribosomally, suggesting that Planktothrix resists chytrids by relying on metabolites that are produced via distinct biosynthetic pathways. Chytrids, on the other hand, can adapt to the oligopeptides produced by Planktothrix in different ways. This setting most likely results in an evolutionary arms race, which would probably lead to Planktothrix and chytrid population structures that closely resemble those actually found in nature. In summary, the findings of the present study suggest oligopeptide production in Planktothrix to be part of a defensive mechanism against chytrid parasitism.
Daniel R Dietrich - One of the best experts on this subject based on the ideXlab platform.
-
oral toxicity of the microcystin containing cyanobacterium Planktothrix rubescens in european whitefish coregonus lavaretus
Aquatic Toxicology, 2006Co-Authors: Bernhard Ernst, Stefan J Hoeger, Evelyn Obrien, Daniel R DietrichAbstract:The microcystin-producing cyanobacterium Planktothrix is one of the most widespread genera amongst toxin producing cyanobacteria in European lakes. In particular, the metalimnic blooms of Planktothrix rubescens have been associated with growing problems in the professional freshwater fishery as a decrease in yearly yields in the important coregonids fishery often coincides with the appearance of P. rubescens. P. rubescens is a cyanobacterial species known to produce toxic compounds, e.g. microcystins. Although microcystins have been reported to affect fish health, behaviour, development and growth and have also been associated with feral fish kills, there is currently no specific information on the effects of toxic Planktothrix filaments in fish and especially coregonids. Therefore, the aim of this study was to investigate the effects of an environmentally relevant dose of P. rubescens filaments orally applied to coregonids and to discuss the findings in the context of microcystin toxicity previously reported in carp and trout. A single dose of P. rubescens culture, at a density of 80,000 cells per 120l, was applied to coregonids thus corresponding to 0.6–0.9g microcystin-LRequiv./kg body weight. Behavioural changes and opercular beat rates, growth, hepatosomatic index, condition and plasma glucose were determined. Liver, kidney, gill and the gastrointestinal tract were assessed histopathologically and immunhistologically. Exposed fish showed behavioural changes, increased opercular beat rates and elevated plasma glucose levels, possibly representing a physiological stress response. Histopathological alterations in liver, gastrointestinal tract and kidney, also immunopositive for microcystin suggested causality of tissue damage and the in situ presence of microcystins. The observed combination of stress and organ damage may explain the frequently reduced weight and thus the fitness noted in coregonids
-
determination of the filamentous cyanobacteria Planktothrix rubescens in environmental water samples using an image processing system
Harmful Algae, 2006Co-Authors: Bernhard Ernst, Stefan J Hoeger, Evelyn Obrien, Stephan Neser, Daniel R DietrichAbstract:Cyanobacteria occur in surface waters worldwide. Many of these produce peptides and/or alkaloids, which can present a risk for animal and human health. Effective risk assessment and management requires continuous and precise observation and quantification of cyanobacterial cell densities. In this respect, quantification of filamentous Planktothrix species is problematic. The aim of this study was to develop an automated system to count filamentous Planktothrix rubescens using image processing. Furthermore, this study aimed to assess optimum sample volumes and filament density for measurement precision and to validate image processing measurement of P. rubescens for an effective risk assessment. Three environmental samples and one cultured sample of P. rubescens were collected by filtration onto nitrocellulose filters. Filament lengths were determined using fluorescence microscopy combined with an image processor. Cell density could be calculated from the resulting images. Cyanobacteria could easily be discriminated from algae via their fluorescence properties. The results were found to be independent of the mode of image acquisition. The precision of total filament length determination was dependent on the total filament length on the filter, i.e. analyses of highest precision could be expected for filters containing 2000‐ 20,000 mmfilaments permm 2 .When using suitablefiltrationvolumes, thedetection limits ofthe described method aresufficient for an effective risk assessment. To summarise, this procedure is a fast, easy and accurate method to determine cell densities of filamentous P. rubescens in water samples without costly and tedious manual handling. # 2005 Elsevier B.V. All rights reserved.
-
presence of Planktothrix sp and cyanobacterial toxins in lake ammersee germany and their impact on whitefish coregonus lavaretus l
Environmental Toxicology, 2001Co-Authors: Bernhard Ernst, Bettina C Hitzfeld, Daniel R DietrichAbstract:Due to the increasing oligotrophy of Lake Ammersee, southern Germany, metalimnic Planktothrix have become one of the dominant planktonic species causing regular blooms. Whitefish (Coregonus lavaretus) is the dominant local fish species with great importance for the fishing industry. Recently, whole age groups of this fish species have disappeared and since 1991, average body-weight has decreased. The causes for this remain unclear. Planktothrix species produce the cyclic peptide toxin desmethyl microcystin-RR, which inhibits glycogen metabolism and has detrimental effects on the development of aquatic organisms. During blooms, gut contents of whitefish displayed a blue discol- oration, possibly representing phycobiliproteins typical for cyanobacteria. This study aimed to elucidate the impact of Planktothrix blooms on fish population dynamics. Planktothrix cell counts, performed by epifluorescence microscopy, showed blooms to contain up to 80,000 cells/ml. Microcystin levels of 1−5 µg/mg dry weight in Planktothrix extracts and 0.08 µg/l in water samples, were determined via HPLC and protein-phosphatase inhibition assay. Planktothrix filaments were detected in gut contents of white- fish. In addition, microcystins could be detected in gut contents via ELISA. Similarly, immunoprobing with microcystin-antibodies demonstrated microcystin-protein adducts in liver homogenates of whitefish caught during Planktothrix blooms. Furthermore, Planktothrix extracts proved cytotoxic to trout hepato- cytes as determined by MTT reduction. Whitefish eggs and larvae, obtained during blooms in winter 1998 and 2000 in a Lake Ammersee hatchery, were studied for developmental progress. Malformations typical for cyanobacterial toxin exposure were observed. © 2001 by John Wiley & Sons, Inc. Environ Toxicol 16: 483-488, 2001
Guntram Christiansen - One of the best experts on this subject based on the ideXlab platform.
-
Genetic identification of microcystin ecotypes in toxic cyanobacteria of the genus Planktothrix.
Microbiology (Reading England), 2020Co-Authors: Rainer Kurmayer, Guntram Christiansen, Marlies Gumpenberger, Jutta FastnerAbstract:Microcystins (MCs) are toxic heptapeptides which are synthesized by the filamentous cyanobacterium Planktothrix and other genera via non-ribosomal peptide synthesis. MCs share the common structure cyclo(-D-ala1-L-X2-D-erythro-beta-iso-aspartic acid3-L-Z4-adda5-D-Glu6-N-methyl-dehydroalanine7) [Adda; (2S, 3S, 8S, 9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid], in which numerous MC variants have been reported. In general, the variation in structure is due to different amino acid residues in positions 7, 2 and 4 within the MC molecule, which are thought to be activated by the adenylation domains mcyAAd1, mcyBAd1 and mcyCAd, respectively. It was the aim of the study (i) to identify MC ecotypes that differed in the production of specific MC variants and (ii) to correlate the genetic variation within adenylation domains with the observed MC variants among 17 Planktothrix strains. Comparison of the sequences of mcyAAd1 revealed two distinctive Ad-genotypes differing in base pair composition and the insertion of an N-methyl transferase (NMT) domain. The mcyAAd1 genotype with NMT (2854 bp) correlated with N-methyl-dehydroalanine and the mcyAAd1 genotype without NMT (1692 bp) correlated with dehydrobutyrine in position 7. Within mcyBAd1, a lower genetic variation (0-4 %) and an exclusive correlation between one Ad-genotype and homotyrosine as well as another Ad-genotype and arginine in position 2 was found. The sequences of mcyCAd were found to be highly similar (0-1 % dissimilarity) and all strains contained arginine in position 4. The results on adenylation domain polymorphism do provide insights into the evolutionary origin of adenylation domains in Planktothrix and may be combined with ecological research in order to provide clues about the abundance of genetically defined MC ecotypes in nature.
-
Emergence of nontoxic mutants as revealed by single filament analysis in bloom-forming cyanobacteria of the genus Planktothrix
BMC Microbiology, 2016Co-Authors: Qin Chen, Guntram Christiansen, Li Deng, Rainer KurmayerAbstract:BackgroundBloom-forming cyanobacteria cause toxic algae outbreaks in lakes and reservoirs. We aimed to explore and quantify mutation events occurring within the large mcy gene cluster (55 kbp) encoding microcystin (MC) biosynthesis that inactivate MC net production. For this purpose we developed a workflow to detect mutations in situ occurring anywhere within the large mcy gene cluster as amplified from one single filament of the red-pigmented cyanobacterium Planktothrix rubescens. From five lakes of the Alps eight hundred Planktothrix filaments were isolated and each individual filament was analyzed for mutations affecting the mcy genes.ResultsMutations inactivating MC synthesis were either through an insertion element ISPlr1 or the partial deletion of mcy genes. Neutral mutations not affecting MC biosynthesis occurred within two intergenic spacer regions, either through the insertion of a Holliday-junction resolvase RusA or ISPlr1. Altogether, the insertions affected a few mcy genes only and their location was correlated with regions similar to repetitive extragenic palindromic DNA sequences (REPs). Taking all of the filaments together, the mutations leading to the inactivation of MC synthesis were more rare (0.5–6.9 %), when compared with the neutral mutations (7.5–20.6 %). On a spatial-temporal scale the ratio of MC synthesis-inactivating vs. neutral mutations was variable, e.g., the filament abundance carrying partial deletion of mcyD (5.2–19.4 %) and/or mcyHA (0–7.3 %) exceeded the abundance of neutral mutations.ConclusionsIt is concluded that insertion events occurring within the Planktothrix mcy gene cluster are predictable due to their correlation with REPs. The frequency of occurrence of the REPs within the mcy gene cluster of Planktothrix relates to the rather common mutation of mcy genes in Planktothrix. Spatial-temporal variable conditions may favor the emergence of partial mcy deletion mutants in Planktothrix, in particular a higher proportion of genotypes resulting in inactivation of MC synthesis might be caused by increased ISPlr1 activity.
-
emergence of nontoxic mutants as revealed by single filament analysis in bloom forming cyanobacteria of the genus Planktothrix
BMC Microbiology, 2016Co-Authors: Qin Chen, Guntram Christiansen, Li Deng, Rainer KurmayerAbstract:Background Bloom-forming cyanobacteria cause toxic algae outbreaks in lakes and reservoirs. We aimed to explore and quantify mutation events occurring within the large mcy gene cluster (55 kbp) encoding microcystin (MC) biosynthesis that inactivate MC net production. For this purpose we developed a workflow to detect mutations in situ occurring anywhere within the large mcy gene cluster as amplified from one single filament of the red-pigmented cyanobacterium Planktothrix rubescens. From five lakes of the Alps eight hundred Planktothrix filaments were isolated and each individual filament was analyzed for mutations affecting the mcy genes.
-
putative antiparasite defensive system involving ribosomal and nonribosomal oligopeptides in cyanobacteria of the genus Planktothrix
Applied and Environmental Microbiology, 2013Co-Authors: Thomas Rohrlack, Guntram Christiansen, Rainer KurmayerAbstract:Parasitic chytrid fungi can inflict significant mortality on cyanobacteria but frequently fail to keep cyanobacterial dominance and bloom formation in check. Our study tested whether oligopeptide production, a common feature in many cyanobacteria, can be a defensive mechanism against chytrid parasitism. The study employed the cyanobacterial strain Planktothrix NIVA-CYA126/8 and its mutants with knockout mutations for microcystins, anabaenopeptins, and microviridins, major oligopeptide classes to be found in NIVA-CYA126/8. Four chytrid strains were used as parasite models. They are obligate parasites of Planktothrix and are unable to exploit alternative food sources. All chytrid strains were less virulent to the NIVA-CYA126/8 wild type than to at least one of its oligopeptide knockout mutants. One chytrid strain even failed to infect the wild type, while exhibiting considerable virulence to all mutants. It is therefore evident that producing microcystins, microviridins, and/or anabaenopeptins can reduce the virulence of chytrids to Planktothrix, thereby increasing the host's chance of survival. Microcystins and anabaenopeptins are nonribosomal oligopeptides, while microviridins are produced ribosomally, suggesting that Planktothrix resists chytrids by relying on metabolites that are produced via distinct biosynthetic pathways. Chytrids, on the other hand, can adapt to the oligopeptides produced by Planktothrix in different ways. This setting most likely results in an evolutionary arms race, which would probably lead to Planktothrix and chytrid population structures that closely resemble those actually found in nature. In summary, the findings of the present study suggest oligopeptide production in Planktothrix to be part of a defensive mechanism against chytrid parasitism.
-
isolation and structure determination of two microcystins and sequence comparison of the mcyabc adenylation domains in Planktothrix species
Journal of Natural Products, 2008Co-Authors: Guntram Christiansen, Karl Gademann, Judith F Blom, Wesley Y Yoshida, Cyril Portmann, Thomas K Hemscheidt, Rainer KurmayerAbstract:Microcystins (MCs) are toxic heptapeptides found in cyanobacteria and share the common structure cyclo(-d-Ala1-l-X2-d-isoMeAsp3-l-Z4-Adda5-d-isoGlu6-Mdha7). The letters X and Z in the general formula above represent a wide range of l-amino acids that occupy positions 2 and 4, respectively. In general the variation in structural variants is due to the exchange of amino acids in position 7, 2, and 4. In the present work we report two homotyrosine (Hty)-containing microcystin variants, [d-Asp3,(E)-Dhb7]-MC-HtyY (1) and [d-Asp3,(E)-Dhb7]-MC-HtyHty (2), which were isolated from strain No80 of Planktothrix rubescens. Their structures were elucidated using amino acid analysis as well as 1D and 2D NMR techniques. The adenylation domains of McyABC involved in amino acid activation in positions 7, 2, and 4 of the microcystin molecule, respectively, were compared with corresponding genes of Planktothrix strain CYA126/8 producing [d-Asp3,Mdha7]-MC-RR and [d-Asp3,Mdha7]-MC-LR. While the adenylation domain comparison o...
Kjetill S Jakobsen - One of the best experts on this subject based on the ideXlab platform.
-
from green to red horizontal gene transfer of the phycoerythrin gene cluster between Planktothrix strains
Applied and Environmental Microbiology, 2013Co-Authors: Ave Toomingklunderud, Thomas Rohrlack, Hanne Sogge, Trine B Rounge, P K Hayes, Alexander J Nederbragt, Karin Lagesen, Gernot Glockner, Kjetill S JakobsenAbstract:Horizontal gene transfer is common in cyanobacteria, and transfer of large gene clusters may lead to acquisition of new functions and conceivably niche adaption. In the present study, we demonstrate that horizontal gene transfer between closely related Planktothrix strains can explain the production of the same oligopeptide isoforms by strains of different colors. Comparison of the genomes of eight Planktothrix strains revealed that strains producing the same oligopeptide isoforms are closely related, regardless of color. We have investigated genes involved in the synthesis of the photosynthetic pigments phycocyanin and phycoerythrin, which are responsible for green and red appearance, respectively. Sequence comparisons suggest the transfer of a functional phycoerythrin gene cluster generating a red phenotype in a strain that is otherwise more closely related to green strains. Our data show that the insertion of a DNA fragment containing the 19.7-kb phycoerythrin gene cluster has been facilitated by homologous recombination, also replacing a region of the phycocyanin operon. These findings demonstrate that large DNA fragments spanning entire functional gene clusters can be effectively transferred between closely related cyanobacterial strains and result in a changed phenotype. Further, the results shed new light on the discussion of the role of horizontal gene transfer in the sporadic distribution of large gene clusters in cyanobacteria, as well as the appearance of red and green strains.
-
gene flow recombination and selection in cyanobacteria population structure of geographically related Planktothrix freshwater strains
Applied and Environmental Microbiology, 2013Co-Authors: Hanne Sogge, Thomas Rohrlack, Trine B Rounge, Jorn Henrik Sonstebo, Ave Toomingklunderud, Tom Kristensen, Kjetill S JakobsenAbstract:ABSTRACT Several Planktothrix strains, each producing a distinct oligopeptide profile, have been shown to coexist within Lake Steinsfjorden (Norway). Using nonribosomal peptide synthetase (NRPS) genes as markers, it has been shown that the Planktothrix community comprises distinct genetic variants displaying differences in bloom dynamics, suggesting a Planktothrix subpopulation structure. Here, we investigate the Planktothrix variants inhabiting four lakes in southeast of Norway utilizing both NRPS and non-NRPS genes. Phylogenetic analyses showed similar topologies for both NRPS and non-NRPS genes, and the lakes appear to have similar structuring of Planktothrix genetic variants. The structure of distinct variants was also supported by very low genetic diversity within variants compared to the between-variant diversity. Incongruent topologies and split decomposition revealed recombination events between Planktothrix variants. In several strains the gene variants seem to be a result of recombination. Both NRPS and non-NRPS genes are dominated by purifying selection; however, sites subjected to positive selection were also detected. The presence of similar and well-separated Planktothrix variants with low internal genetic diversity indicates gene flow within Planktothrix populations. Further, the low genetic diversity found between lakes (similar range as within lakes) indicates gene flow also between Planktothrix populations and suggests recent, or recurrent, dispersals. Our data also indicate that recombination has resulted in new genetic variants. Stability within variants and the development of new variants are likely to be influenced by selection patterns and within-variant homologous recombination.
-
a genome wide analysis of nonribosomal peptide synthetase gene clusters and their peptides in a Planktothrix rubescens strain
BMC Genomics, 2009Co-Authors: Trine B Rounge, Thomas Rohrlack, Tom Kristensen, Alexander J Nederbragt, Kjetill S JakobsenAbstract:Background Cyanobacteria often produce several different oligopeptides, with unknown biological functions, by nonribosomal peptide synthetases (NRPS). Although some cyanobacterial NRPS gene cluster types are well described, the entire NRPS genomic content within a single cyanobacterial strain has never been investigated. Here we have combined a genome-wide analysis using massive parallel pyrosequencing ("454") and mass spectrometry screening of oligopeptides produced in the strain Planktothrix rubescens NIVA CYA 98 in order to identify all putative gene clusters for oligopeptides.
-
recombination and selectional forces in cyanopeptolin nrps operons from highly similar but geographically remote Planktothrix strains
BMC Microbiology, 2008Co-Authors: Trine B Rounge, Thomas Rohrlack, Tom Kristensen, Kjetill S JakobsenAbstract:Background Cyanopeptolins are nonribosomally produced heptapetides showing a highly variable composition. The cyanopeptolin synthetase operon has previously been investigated in three strains from the genera Microcystis, Planktothrix and Anabaena. Cyanopeptolins are displaying protease inhibitor activity, but the biological function(s) is (are) unknown. Cyanopeptolin gene cluster variability and biological functions of the peptide variants are likely to be interconnected.
-
comparison of cyanopeptolin genes in Planktothrix microcystis and anabaena strains evidence for independent evolution within each genus
Applied and Environmental Microbiology, 2007Co-Authors: Trine B Rounge, Thomas Rohrlack, Ave Toomingklunderud, Tom Kristensen, Kjetill S JakobsenAbstract:The major cyclic peptide cyanopeptolin 1138, produced by Planktothrix strain NIVA CYA 116, was characterized and shown to be structurally very close to the earlier-characterized oscillapeptin E. A cyanopeptolin gene cluster likely to encode the corresponding peptide synthetase was sequenced from the same strain. The 30-kb oci gene cluster contains two novel domains previously not detected in nonribosomal peptide synthetase gene clusters (a putative glyceric acid-activating domain and a sulfotransferase domain), in addition to seven nonribosomal peptide synthetase modules. Unlike in two previously described cyanopeptolin gene clusters from Anabaena and Microcystis, a halogenase gene is not present. The three cyanopeptolin gene clusters show similar gene and domain arrangements, while the binding pocket signatures deduced from the adenylation domain sequences and the additional tailoring domains vary. This suggests loss and gain of tailoring domains within each genus, after the diversification of the three clades, as major events leading to the present diversity. The ABC transporter genes associated with the cyanopeptolin gene clusters form a monophyletic clade and accordingly are likely to have evolved as part of the functional unit. Phylogenetic analyses of adenylation and condensation domains, including domains from cyanopeptolins and microcystins, show a closer similarity between the Planktothrix and Microcystis cyanopeptolin domains than between these and the Anabaena domain. No clear evidence of recombination between cyanopeptolins and microcystins could be detected. There were no strong indications of horizontal gene transfer of cyanopeptolin gene sequences across the three genera, supporting independent evolution within each genus.
