Browsing by Subject "nodulariini"

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  • Heinilä, Lassi Matti Petteri (Helsingin yliopisto, 2017)
    Cyanobacteria, also referred as blue-green algae, are abundant everywhere on earth inhabi-ting terrestrial and marine environments and living in symbiosis with several other organisms. Cyanobacteria were the first oxygenic photosynthetic organisms on earth and many species are also capable of fixing atmospheric nitrogen which makes them important primary produ-cers in many ecosystems. Cyanobacteria are nevertheless best known for producing toxic compounds. Cyanobacteria produce a variety of bioactive compounds including toxic ones. Some of these compounds have a potential as drugs. Most of these compounds are produ-ced by nonribosomal peptide synthetases and polyketide synthases. Nostoc sp. CENA543 is a cyanobacteria isolated from Brazilian wetland Pantanal. The strain was found to produce hepatptoxic nodularin, bioactive anabaenopeptins and a pre-viously unkown peptide. In this work the chemical structure and the biosynthetic gene cluster of the unkown peptide were characterized. Amount of produced nodularin was measured and biosynthetic genes of nodularin and anabaenopeptins were examined. Also the optimal growth conditions for the strain were studied. Essential methods applied in this work were liquid cromatography and mass spectromet-ry. To examine the biosynthetic genes DNA extraction methods and bioinformatic tools such as AntiSMASH, BLAST, Artemis and BioEdit were applied. The growth conditions were in-vestigated on different growth media. Bioactivity of the compounds were examined on disc diffusion assays and with the Kawabata method for enzyme activity. The results of this study show that Nostoc sp. CENA543 produces toxic amounts of no-dularin. The novel peptide group was named pseudospumigins. Six variants of pseudospu-migins were observed, the main variant being pseudospumigin A. Amino acid sequence of pseudospumigin A is Hpla-D-Hty-L-Ile-Argininal with mass of 612,4 Da. Gene clusters of nodularin and anabaenopeptin match corresponding genes of Nodularia spuimigena CCY9414. The biosynthetic genes of pseudospumigin have high resemblance to spumigin genecluster of Nodularia spuimigena CCY9414. Change in adenylation domain substrate specificity and deletion of three additional genes would axplain the difference between pseu-dospumigins and spumigins.
  • Wood, Steffaney M.; Kremp, Anke; Savela, Henna; Akter, Sultana; Vartti, Vesa-Pekka; Saarni, Saija; Suikkanen, Sanna (Frontiers in Microbiology, 2021)
    Frontiers in Microbiology 12
    Cyanobacteria of the order Nostocales, including Baltic Sea bloom-forming taxa Nodularia spumigena, Aphanizomenon flosaquae, and Dolichospermum spp., produce resting stages, known as akinetes, under unfavorable conditions. These akinetes can persist in the sediment and germinate if favorable conditions return, simultaneously representing past blooms and possibly contributing to future bloom formation. The present study characterized cyanobacterial akinete survival, germination, and potential cyanotoxin production in brackish water sediment archives from coastal and open Gulf of Finland in order to understand recent bloom expansion, akinete persistence, and cyanobacteria life cycles in the northern Baltic Sea. Results showed that cyanobacterial akinetes can persist in and germinate from Northern Baltic Sea sediment up to >40 and >400 years old, at coastal and open-sea locations, respectively. Akinete abundance and viability decreased with age and depth of vertical sediment layers. The detection of potential microcystin and nodularin production from akinetes was minimal and restricted to the surface sediment layers. Phylogenetic analysis of culturable cyanobacteria from the coastal sediment core indicated that most strains likely belonged to the benthic genus Anabaena. Potentially planktonic species of Dolichospermum could only be revived from the near-surface layers of the sediment, corresponding to an estimated age of 1–3 years. Results of germination experiments supported the notion that akinetes do not play an equally significant role in the life cycles of all bloom-forming cyanobacteria in the Baltic Sea. Overall, there was minimal congruence between akinete abundance, cyanotoxin concentration, and the presence of cyanotoxin biosynthetic genes in either sediment core. Further research is recommended to accurately detect and quantify akinetes and cyanotoxin genes from brackish water sediment samples in order to further describe species-specific benthic archives of cyanobacteria.
  • Agge, Ursula (University of Helsinki, 1995)