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Variation in expression of nodularin synthetase gene in Nodularia spumigena with salinity
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. (Marine Phytoplankton ecology and applications)
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
Abstract [en]

Cyanobacterial blooms in the Baltic Sea are a continuous event during summer and are principally dominated by Nodularia spumigena, which is a toxin producer of the hepatotoxin nodularin. During the last decades cyanobacterial blooms have increased, being a threat to both ecosystem and human integrity. One of the major concerns is how climate change, principally the salinity decrease, will affect these cyanobacterial proliferations in the Baltic Sea and which mechanisms control nodularin production. We studied Nodularia spumigena strain KAC11 as a model species to test salinity effects on growth rates, intracellular nodularin concentration and expression levels of nodularin synthetase gene (ndaF). Intracellular nodularin concentrations remained relatively stable regardless of growth phase and salinity while gene expression varied 2-3 fold during the course of the experiment. Thus, downward salinity changes did not influence the relative gene expression of ndaF. No direct relation was found between intracellular nodularin and gene expression, suggesting that in laboratory cultures nodularin could be degraded or excreted. This also questions the potential use of this technique for monitoring toxin concentrations in environmental samples. Compared to other studies, high intraspecific variation in growth and toxin levels was found within Nodularia strains, showing variation in autoecological responses related to different salinities. Considering that blooms consist of diverse strains of N. spumigena in nature, it would require more transcriptional studies to investigate the effect of environmental factors on nodularin biosynthesis. 

Abstract [sv]

Blommande cyanobakterier i östersjön är ett stående inslag under sommaren. Dessa blomningar domineras av Nodularia spumigena som producerar levertoxinet nodularin. Blomningar av cyanobakterier har ökat de senaste årtionden, vilket medför störningar i ekosystemet och är ett hot mot mänsklig hälsa. En av de stora angelägenheterna är hur klimatförändringar kommer att påverka spridningen av cyanobakterier i östersjön då särskilt salthalten, som anses kontrollera nodularinproduktionen, kommer att minska. Vi studerade Nodularia spumigena stam KAC11 som modellart för att testa effekten av salthalt på tillväxthastighet, intracellular nodularinkoncentration och uttrycksnivåer av syntetasgenen för nodularin (ndaF). Den intracellulära nodularinkoncentrationen var relativt stabil oavsett tillväxtfas och salthalt medan genuttrycket varierade 2-3-faldigt under experimentet. Således påverkade inte minskad salthalt genuttrycket för ndaF. Inget samband hittades mellan intracellulär nodularinkoncentration och genuttryck, vilket tyder på att nodularin i laboratoriekulturer skulle kunna brytas ner eller utsöndras. Detta ifrågasätter också den potentiella användbarheten av den här tekniken för övervakning av toxinkoncentrationer i miljöprover. Stor variation gällande tillväxt och toxinnivåer inom samma stammar av Nodularia påträffades, vilket visar på en variation i autoekologisk respons relaterad till olika salthalter. Med tanke på att naturliga blomningar består av diverse stammar av N. spumigena skulle det krävas fler transkriptionella studier för att undersöka effekten av miljöfaktorer på biosyntes av nodularin.

Place, publisher, year, edition, pages
2014. , p. 30
Keywords [en]
Nodularia spumigena, salinity, nodularin, gene expression
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:lnu:diva-31800OAI: oai:DiVA.org:lnu-31800DiVA, id: diva2:692169
Subject / course
Biology
Educational program
Akvatisk ekologi, masterprogram, 120 hp
Supervisors
Examiners
Available from: 2014-02-07 Created: 2014-01-29 Last updated: 2014-02-07Bibliographically approved

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CiteExportLink to record
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