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Expression of the nodularin synthetase genes in the Baltic Sea bloom-former cyanobacterium Nodularia spumigena strain AV1.
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
Stockholm University, Faculty of Science, Department of Botany.
2008 (English)In: FEMS Microbiol Ecol, ISSN 0168-6496, Vol. 65, no 1, 31-39 p.Article in journal (Refereed) Published
Abstract [en]

Cyanobacterial blooms in the Baltic Sea are a common phenomenon and are formed by the heterocystous, filamentous species Nodularia spumigena. The toxicity of these blooms is attributed to the hepatotoxin nodularin, produced by N. spumigena. Little is known regarding the regulatory mechanisms or environmental signaling that control nodularin production. Here we report the characterization of the transcriptional expression pattern of the nodularin synthetase gene cluster (nda) during phosphate depletion, and nitrogen supplementation. Real-time PCR analysis of these genes revealed that while cells continuously expressed the nda cluster, the expression of all nda genes increased when cells were subjected to phosphate depletion, and decreased in the presence of ammonium. In contrast to the shifts in expression, the intracellular and extracellular nodularin concentrations did not vary significantly during the treatments.

Place, publisher, year, edition, pages
2008. Vol. 65, no 1, 31-39 p.
Keyword [en]
Gene Expression Regulation; Bacterial, Ligases/*genetics/metabolism, Multigene Family, Nitrogen/metabolism, Nodularia/classification/*enzymology/genetics/growth & development, Peptides; Cyclic/*metabolism, Phosphates/metabolism, RNA; Bacterial/genetics/isolation & purification/metabolism, RNA; Messenger/genetics/metabolism, Reverse Transcriptase Polymerase Chain Reaction, Seawater/*microbiology, Sweden
Identifiers
URN: urn:nbn:se:su:diva-18476DOI: 10.1111/j.1574-6941.2008.00499.xISI: 000256717200003PubMedID: 18503549OAI: oai:DiVA.org:su-18476DiVA: diva2:184999
Available from: 2009-01-26 Created: 2009-01-26 Last updated: 2009-09-01Bibliographically approved
In thesis
1. Functional genomics of the Baltic Sea cyanobacterium Nodularia spumigena in relation to nitrogen fixation, heterocyst differentiation and toxin production
Open this publication in new window or tab >>Functional genomics of the Baltic Sea cyanobacterium Nodularia spumigena in relation to nitrogen fixation, heterocyst differentiation and toxin production
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nodularia spumigena is a filamentous, heterocystous cyanobacterium that dominates the annual, toxic cyanobacterial blooms in the Baltic Sea. The blooms are believed to have increased in recent years, due to eutrophication by phosphate and/or nitrogen. Toxicity of these blooms is well-documented and attributed to the hepatotoxin nodularin. The focus of this study was to characterize nitrogen fixation and toxin production of Nodularia spumigena, in response to various levels of combined nitrogen and phosphate. In the presence of combined nitrogen, several Nodularia spumigena strains lost aerobic nitrogen fixation activity while the heterocyst frequency along the filaments remained unchanged. The expression of nifH dropped in response to the treatment, while the expression patterns of ntcA and hetR (key genes controlling heterocyst differentiation) were not affected. It is therefore concluded that in Nodularia, nitrogen fixation and heterocyst differentiation are uncoupled. Protein profiling during ammonium supplementation revealed differential expression of 28 proteins. Proteins involved in energy metabolism, carbon and nitrogen fixation were down-regulated during ammonium supplementation while stress-related proteins were up-regulated, further indicating that N. spumigena does not benefit from ammonium supplementation. Analysis of the nodularin synthetase (nda) gene expression demonstrated an increase of all the nine nda genes upon phosphate depletion and decrease of expression in the presence of combined nitrogen. In contrast to shifts in expression, the intra- and extracellular nodularin concentrations did not vary significantly, suggesting a transcriptionally-independent regulation of nodularin biosynthesis. Together, these data suggest that neither nitrogen nor phosphate alone, especially the low levels encountered in the Baltic Sea, affects heterocyst formation and nodularin biosynthesis.

Place, publisher, year, edition, pages
Stockholm: Department of Botany, Stockholm University, 2009. 61 p.
Keyword
cyanobacteria, Nodularia, nitrogen fixation, heterocyst, nitrogenase, ammonium, phosphate, nodularin, Baltic Sea
National Category
Botany
Research subject
Plant Physiology
Identifiers
urn:nbn:se:su:diva-29495 (URN)978-91-7155-935-7 (ISBN)
Public defence
2009-10-02, Föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 10:00 (English)
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Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript. Paper 5: ManuscriptAvailable from: 2009-09-10 Created: 2009-09-01 Last updated: 2009-09-01Bibliographically approved

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