Adaptation of a chytrid parasite to Its cyanobacterial host Is hampered by host intraspecific diversity

Experimental evolution can be used to test for and characterize parasite and pathogen adaptation. We undertook a serial-passage experiment in which a single parasite population of the obligate fungal (chytrid) parasite Rhizophydium megarrhizum was maintained over a period of 200 days under different mono- and multiclonal compositions of its phytoplankton host, the bloom-forming cyanobacterium Planktothrix. Despite initially inferior performance, parasite populations under sustained exposure to novel monoclonal hosts experienced rapid fitness increases evidenced by increased transmission rates. This demonstrates rapid adaptation of chytrids to novel hosts and highlights their high evolutionary potential. In contrast, increased fitness was not detected in parasites exposed to multiclonal host mixtures, indicating that cyanobacterial intraspecific diversity hampers parasites adaptation. Significant increases in intensity of infection were observed in monoclonal and multiclonal treatments, suggesting high evolvability of traits involved in parasite attachment onto hosts (i.e., encystment). A comparison of the performance of evolved and unevolved (control) parasite populations against their common ancestral host did not reveal parasite attenuation. Our results exemplify the ability of chytrid parasites to adapt rapidly to new hosts, while providing experimental evidence that genetic diversity in host populations grants increased resistance to disease by hindering parasite adaptation

Adaptation of a chytrid parasite to Its cyanobacterial host Is hampered by host intraspecific diversity

Experimental evolution can be used to test for and characterize parasite and pathogen adaptation. We undertook a serial-passage experiment in which a single parasite population of the obligate fungal (chytrid) parasite Rhizophydium megarrhizum was maintained over a period of 200 days under different mono- and multiclonal compositions of its phytoplankton host, the bloom-forming cyanobacterium Planktothrix. Despite initially inferior performance, parasite populations under sustained exposure to novel monoclonal hosts experienced rapid fitness increases evidenced by increased transmission rates. This demonstrates rapid adaptation of chytrids to novel hosts and highlights their high evolutionary potential. In contrast, increased fitness was not detected in parasites exposed to multiclonal host mixtures, indicating that cyanobacterial intraspecific diversity hampers parasites adaptation. Significant increases in intensity of infection were observed in monoclonal and multiclonal treatments, suggesting high evolvability of traits involved in parasite attachment onto hosts (i.e., encystment). A comparison of the performance of evolved and unevolved (control) parasite populations against their common ancestral host did not reveal parasite attenuation. Our results exemplify the ability of chytrid parasites to adapt rapidly to new hosts, while providing experimental evidence that genetic diversity in host populations grants increased resistance to disease by hindering parasite adaptation

Chytrid parasitism facilitates trophic transfer between bloom-forming cyanobacteria and zooplankton (Daphnia)

Parasites are rarely included in food web studies, although they can strongly alter trophic interactions. In aquatic ecosystems, poorly grazed cyanobacteria often dominate phytoplankton communities, leading to the decoupling of primary and secondary production. Here, we addressed the interface between predator-prey and host-parasite interactions by conducting a life-table experiment, in which four Daphnia galeata genotypes were maintained on quantitatively comparable diets consisting of healthy cyanobacteria or cyanobacteria infected by a fungal (chytrid) parasite. In four out of five fitness parameters, at least one Daphnia genotype performed better on parasitised cyanobacteria than in the absence of infection. Further treatments consisting of purified chytrid zoospores and heterotrophic bacteria suspensions established the causes of improved fitness. First, Daphnia feed on chytrid zoospores which trophically upgrade cyanobacterial carbon. Second, an increase in heterotrophic bacterial biomass, promoted by cyanobacterial decay, provides an additional food source for Daphnia. In addition, chytrid infection induces fragmentation of cyanobacterial filaments, which could render cyanobacteria more edible. Our results demonstrate that chytrid parasitism can sustain zooplankton under cyanobacterial bloom conditions, and exemplify the potential of parasites to alter interactions between trophic levels

Utprøving av endret manøvreringsreglement i Vansjø - Resultater fra sommeren 2008

Vannkvaliteten i Vansjø og Mosseelva sommeren 2008 er vurdert i forhold til manøvreringen av innsjøen. Sommeren 2008 var meget spesiell med store ras og derfor høy partikkeltilførsel til innsjøen. Det er derfor vanskelig å avgjøre hvilke forhold som har ført til en bedre vannkvalitet. Imidlertid tyder data fra en sensor ved Mossefossen på at temperaturen og pH reduseres når gjennomstrømningen øker, noe som tyder på redusert algeproduksjon i denne delen av innsjøsystemet. Problemalgene i Vanemfjorden og Mosseelva (Microcystis sp. og Anabaena sp.) trives dessuten best ved høye temperaturer og relativt stabil sjiktning. Ettersom fordelene ved det endrete reglementet er undersøkt anbefales det å se nærmere på eventuelle ulemper knyttet til høy vannstand om våren, som kan gi økt næringstilførsel og også økt fare for skadeflom.publishedVersio

Recombination and selectional forces in cyanopeptolin NRPS operons from highly similar, but geographically remote Planktothrix strains

<p>Abstract</p> <p>Background</p> <p>Cyanopeptolins are nonribosomally produced heptapetides showing a highly variable composition. The cyanopeptolin synthetase operon has previously been investigated in three strains from the genera <it>Microcystis</it>, <it>Planktothrix </it>and <it>Anabaena</it>. 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.</p> <p>Results</p> <p>We have investigated two cyanopeptolin gene clusters from highly similar, but geographically remote strains of the same genus. Sequencing of a nonribosomal peptide synthetase (NRPS) cyanopeptolin gene cluster from the Japanese strain <it>Planktothrix </it>NIES 205 (205-<it>oci</it>), showed the 30 kb gene cluster to be highly similar to the <it>oci </it>gene cluster previously described in <it>Planktothrix </it>NIVA CYA 116, isolated in Norway. Both operons contained seven NRPS modules, a sulfotransferase (S) and a glyceric acid loading (GA)-domain. Sequence analyses showed a high degree of conservation, except for the presence of an epimerase domain in NIES 205 and the regions around the epimerase, showing high substitution rates and Ka/Ks values above 1. The two strains produce almost identical cyanopeptolins, cyanopeptolin-1138 and oscillapeptin E respectively, but with slight differences regarding the production of minor cyanopeptolin variants. These variants may be the result of relaxed adenylation (A)-domain specificity in the nonribosomal enzyme complex. Other genetic markers (16S rRNA, <it>ntc</it>A and the phycocyanin <it>cpc</it>BA spacer) were identical, supporting that these geographically separated <it>Planktothrix </it>strains are closely related.</p> <p>Conclusion</p> <p>A horizontal gene transfer event resulting in exchange of a whole module-encoding region was observed. Nucleotide statistics indicate that both purifying selection and positive selection forces are operating on the gene cluster. The positive selection forces are acting within and around the epimerase insertion while purifying selection conserves the remaining (major) part of the gene cluster. The presence of an epimerase in the gene cluster is in line with the D-configuration of Htyr, determined experimentally in oscillapeptin E in a previous study.</p

DESAIN PEMBELAJARAN BERDASARKAN ANALISIS KESULITAN BELAJAR SISWA BERBASIS COOPERATIVE LEARNING TIPE GROUP INVESTIGATION (GI) PADA KONSEP GAYA MAGNET di KELAS IV SEKOLAH DASAR: Suatu Penelitian Tindakan Kelas Menerapkan Didactical Design Research (DDR) di Kelas IV SD Negeri Taman Baru 01 Tahun 2015

Proses pembelajaran yang terjadi di kelas tediri dari tiga fase essensial meliputi persiapan, pelaksanaan, dan evaluasi. Guru sebagai pelopor dalam mendukung keberhasilan prestasi belajar siswa SD, dalam menyajikan pembelajaran IPA masih belum optimal. Peneliti menemukan pembelajaran berlangsung dikelas menyajikan konsep gaya magnet dilakukan secara klasikal, disertai respon siswa yang pasif yang menyebabkan pembelajaran belum meningkat secara signifikan. Kemungkinan terbesarnya, kurangnya peranan guru dalam memaknai pembelajaran IPA. temuan lainnya menyatakan kesulitan belajar masih dialami anak, didukung melalui kuisioner yang temuan jawaban siswa belum tepat dalam menjawab pada konsep gaya magnet. Mengingat penting pembelajaran IPA di sekolah diperlukannya metode yang tepat yang dapat teratasinya kesulitan belajar dan meningkatkan hasil belajar siswa. Oleh karena itu, yang peneliti menawarkan model pembelajaran penelitian tindakan kelas menerapkan didactical design research, sebagai upaya solutif dalam memecahkan persoalan diatas. Salah satunya, melalui metode Group Investigation. Dalam metode ini, merepresentasikan dalam beberapa episode pembelajaran, dengan penyelidikan temuan IPA melalui berbagai percobaan secara berkelompok. Hasil yang diperoleh produk berupa lesson design, disertai adanya peningkatan setiap siklus dan situasi didaktis yang terjadi menjadikan suasana baru yang menarik bagi anak. Adapun, Penelitian ini dilaksanakan pada bulan Mei-Juni 2015 dengan subjek penelitian berjumlah 41 orang siswa kelas IV SD Negeri Taman Baru I Kecamatan taktakan Kota Serang. Yang terdiri dari 15 siswa laki-laki dan 26 siswi perempuan. Penelitian PTK menerapkan DDR ini dilakukan dalam beberapa tahapan yaitu perencanaan (prospektif), pelaksanaan (metapedadidaktik), pengamatan dan refleksi (retrospektif), yang dibagi kedalam pra siklus, siklus I, dan siklus II. Berdasarkan temuan penelitian, maka pembelajaran IPA dengan mengambil konsep penelitian PTK menerapkan DDR, diperoleh hasil terjadinya peningkatan hasil belajar siswa dan teratasinya kesulitan belajar pada konsep gaya magnet

A genome-wide analysis of nonribosomal peptide synthetase gene clusters and their peptides in a Planktothrix rubescens strain

<p>Abstract</p> <p>Background</p> <p>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 <it>Planktothrix rubescens </it>NIVA CYA 98 in order to identify all putative gene clusters for oligopeptides.</p> <p>Results</p> <p>Thirteen types of oligopeptides were uncovered by mass spectrometry (MS) analyses. Microcystin, cyanopeptolin and aeruginosin synthetases, highly similar to already characterized NRPS, were present in the genome. Two novel NRPS gene clusters were associated with production of anabaenopeptins and microginins, respectively. Sequence-depth of the genome and real-time PCR data revealed three copies of the microginin gene cluster. Since NRPS gene cluster candidates for microviridin and oscillatorin synthesis could not be found, putative (gene encoded) precursor peptide sequences to microviridin and oscillatorin were found in the genes <it>mdn</it>A and <it>osc</it>A, respectively. The genes flanking the microviridin and oscillatorin precursor genes encode putative modifying enzymes of the precursor oligopeptides. We therefore propose ribosomal pathways involving modifications and cyclisation for microviridin and oscillatorin. The microviridin, anabaenopeptin and cyanopeptolin gene clusters are situated in close proximity to each other, constituting an oligopeptide island.</p> <p>Conclusion</p> <p>Altogether seven nonribosomal peptide synthetase (NRPS) gene clusters and two gene clusters putatively encoding ribosomal oligopeptide biosynthetic pathways were revealed. Our results demonstrate that whole genome shotgun sequencing combined with MS-directed determination of oligopeptides successfully can identify NRPS gene clusters and the corresponding oligopeptides. The analyses suggest independent evolution of all NRPS gene clusters as functional units. Our data indicate that the <it>Planktothrix </it>genome displays evolution of dual pathways (NRPS and ribosomal) for production of oligopeptides in order to maximize the diversity of oligopeptides with similar but functional discrete bioactivities.</p

Evidence for positive selection acting on microcystin synthetase adenylation domains in three cyanobacterial genera

<p>Abstract</p> <p>Background</p> <p>Cyanobacteria produce a wealth of secondary metabolites, including the group of small cyclic heptapeptide hepatotoxins that constitutes the microcystin family. The enzyme complex that directs the biosynthesis of microcystin is encoded in a single large gene cluster (<it>mcy</it>). <it>mcy </it>genes have a widespread distribution among cyanobacteria and are likely to have an ancient origin. The notable diversity within some of the Mcy modules is generated through various recombination events including horizontal gene transfer.</p> <p>Results</p> <p>A comparative analysis of the adenylation domains from the first module of McyB (McyB1) and McyC in the microcystin synthetase complex was performed on a large number of microcystin-producing strains from the <it>Anabaena</it>, <it>Microcystis </it>and <it>Planktothrix </it>genera. We found no decisive evidence for recombination between strains from different genera. However, we detected frequent recombination events in the <it>mcyB </it>and <it>mcyC </it>genes between strains within the same genus. Frequent interdomain recombination events were also observed between <it>mcyB </it>and <it>mcyC </it>sequences in <it>Anabaena </it>and <it>Microcystis</it>. Recombination and mutation rate ratios suggest that the diversification of <it>mcyB </it>and <it>mcyC </it>genes is driven by recombination events as well as point mutations in all three genera. Sequence analysis suggests that generally the adenylation domains of the first domain of McyB and McyC are under purifying selection. However, we found clear evidence for positive selection acting on a number of amino acid residues within these adenylation domains. These include residues important for active site selectivity of the adenylation domain, strongly suggesting selection for novel microcystin variants.</p> <p>Conclusion</p> <p>We provide the first clear evidence for positive selection acting on amino acid residues involved directly in the recognition and activation of amino acids incorporated into microcystin, indicating that the microcystin complement of a given strain may influence the ability of a particular strain to interact with its environment.</p

The Cyanobacterial Hepatotoxin Microcystin Binds to Proteins and Increases the Fitness of Microcystis under Oxidative Stress Conditions

Microcystins are cyanobacterial toxins that represent a serious threat to drinking water and recreational lakes worldwide. Here, we show that microcystin fulfils an important function within cells of its natural producer Microcystis. The microcystin deficient mutant ΔmcyB showed significant changes in the accumulation of proteins, including several enzymes of the Calvin cycle, phycobiliproteins and two NADPH-dependent reductases. We have discovered that microcystin binds to a number of these proteins in vivo and that the binding is strongly enhanced under high light and oxidative stress conditions. The nature of this binding was studied using extracts of a microcystin-deficient mutant in vitro. The data obtained provided clear evidence for a covalent interaction of the toxin with cysteine residues of proteins. A detailed investigation of one of the binding partners, the large subunit of RubisCO showed a lower susceptibility to proteases in the presence of microcystin in the wild type. Finally, the mutant defective in microcystin production exhibited a clearly increased sensitivity under high light conditions and after hydrogen peroxide treatment. Taken together, our data suggest a protein-modulating role for microcystin within the producing cell, which represents a new addition to the catalogue of functions that have been discussed for microbial secondary metabolites

Overvåking av Indre Oslofjord i 2011

Denne rapporten gir en kortfattet oversikt over resultatene fra overvåkingen foretatt for Fagrådet for vann- og avløpsteknisk samarbeid i Indre Oslofjord i 2011. En mer utfyllende beskrivelse av resultatene er presentert i en vedleggsrapport (l. nr.6372). Undersøkelsene omfatter fysiske, kjemiske og biologiske forhold. Overgjødsling har vært et hovedtema i overvåkingen, men miljøgiftsproblematikk er nå også inkludert. Overvåkingen i 2011 ble gjennomført av Norsk institutt for vannforskning (NIVA) i samarbeid med Biologisk Institutt ved Universitetet i Oslo (UiO). Havforskningsinstituttet (HI) har også vært involvert.Fagrådet for vann- og avløpsteknis