Iron-stimulated toxin production in Microcystis aeruginosa

Utkilen, Hans; Gjølme, Nina

doi:10.1128/aem.61.2.797-800.1995

Cited by 234 publications

(114 citation statements)

References 16 publications

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“…3). This illustrates that all strains studied here have an efficient iron uptake mechanism and is in contrast to previous reports that toxic M. aeruginosa take up more iron with the inference that, as a result, non-microcystin producers are forced to maintain a smaller intracellular iron reserve (Utkilen and Gjolme, 1995). Due to the differences in the choice of iron transporters for each M. aeruginosa strain, as illustrated by the transcription of feoB and futA, it was of interest to determine where the Fe 3+ -binding protein FutA is localized.…”

Section: Discussioncontrasting

confidence: 82%

“…Microcystin synthesis has been proposed to give a selective advantage to toxic M. aeruginosa cells in iron-limited conditions (Utkilen and Gjolme, 1995). Such properties of this cyclic peptide may contribute to the long-term survival of these microorganisms in water bodies and the prevalence of toxic strains during the early stages of bloom formation in both M. aeruginosa and Planktothrix agardhii (Kardinaal et al, 2007;Briand et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

“…The physiological basis behind the differential response of toxic and non-toxic strains to iron stress remains largely unknown. This is highlighted by several studies investigating toxicity in iron limitation, which have found conflicting results with regards to changes in microcystin synthesis (Utkilen and Gjolme, 1995;Briand et al, 2008;Sevilla et al, 2008). The discrepancies in the literature are usually accounted for by differences in experimental design, in particular, iron concentration, types of metal-binding chelators present in the growth media and growth conditions used, making it difficult to compare the conclusions made by different groups.…”

Section: Discussionmentioning

confidence: 99%

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Iron uptake and toxin synthesis in the bloom‐forming Microcystis aeruginosa under iron limitation

Alexova¹,

Fujii

Birch

et al. 2011

Environmental Microbiology

137

129

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Toxin production during cyanobacterial blooms poses a significant public health threat in water bodies globally and requires the development of effective bloom management strategies. Previously, synthesis of the hepatotoxin microcystin has been proposed to be regulated by iron availability, but the contribution of the toxin to the adaptation of cyanobacteria to environmental stresses, such as changing light intensity and nutrient limitation, remains unclear. The aim of this study was to compare the iron stress response in toxic and non-toxic strains of Microcystis aeruginosa subjected to moderate and severe iron limitation. The transcription of a number of genes involved in iron uptake, oxidative stress response, toxin synthesis and transcriptional control of these processes was accessed by quantitative real-time PCR (qRT-PCR). The process of adaptation of M. aeruginosa to iron stress was found to be highly dynamic and strain-specific. Toxin production in PCC 7806 increased in an iron-dependent manner and appeared to be regulated by FurA. The inability to produce microcystin, either due to natural mutations in the mcy gene cluster or due to insertional inactivation of mcyH, affected the remodelling of the photosynthetic machinery in iron-stressed cells, the transport of Fe(II) and transcription of the Fur family of transcriptional regulators. The presence of the toxin appears to give an advantage to microcystin-producing cyanobacteria in the early stages of exposure to severe iron stress and may protect the cell from reactive oxygen species-induced damage.

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Section: Discussioncontrasting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Iron uptake and toxin synthesis in the bloom‐forming Microcystis aeruginosa under iron limitation

Alexova¹,

Fujii

Birch

et al. 2011

Environmental Microbiology

137

129

View full text Add to dashboard Cite

show abstract

“…Likewise, Microcystis under severe Fe stress (0.01 μmol/L) had significantly higher cellular microcystin concentrations than when cultured with 0.1 or 1 μmol/L of Fe (Alexova et al 2011). However, other studies have reported that higher Fe levels (in the range of 5-16 μmol/L) stimulate microcystin production (Utkilen and Gjølme 1995, Jiang et al 2008, Li et al 2009). Evidently the role of Fe in regulating microcystin requires further research.…”

Section: Hypothesismentioning

confidence: 88%

Experimental iron amendment suppresses toxic cyanobacteria in a hypereutrophic lake

Orihel

Schindler

Ballard

et al. 2016

Ecological Applications

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The effects of reducing nutrient inputs to lakes and reservoirs are often delayed by hysteresis resulting from internal phosphorus (P) loading from sediments. Consequently, controlling harmful algal blooms (HABs) in many eutrophic ecosystems requires additional management to improve water quality. We manipulated iron (Fe) concentrations in a hypereutrophic lake to determine if Fe amendment would suppress HABs by inhibiting P release from sediments. Our experiment consisted of 15 in situ mesocosms, 12 of which each received a different dose of Fe (ranging from 2 to 225 g/m ); the remaining three were unmanipulated to serve as controls. Iron amendment decreased P accumulation in porewaters and the flux of P from sediments, which significantly lowered P concentrations in the water column. Iron exerted significant dose-dependent negative effects on the biomass of phytoplankton and periphyton, and reduced the dominance of cyanobacteria. Even at the lowest doses, Fe appeared to reduce the toxicity of cyanobacterial blooms, as measured by concentrations of hepatotoxic microcystins. Overall, our findings highlight the potential for Fe treatment as an effective strategy for minimizing HABs in eutrophic lakes and reservoirs. More broadly, our study reinforces the importance of Fe in regulating the trophic state of freshwaters, and the sensitivity of certain ecosystems to changes in Fe supply. Finally, we hypothesize that decreases in natural Fe supplies to lakes associated with anthropogenic activities may worsen outbreaks of toxic cyanobacteria.

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“…Also important is the relationship between iron uptake and light intensity. High light intensities increase cellular iron uptake which may ultimately be responsible for higher toxin production [15]. In contrast, low concentrations of iron, implicated in slower cell growth, have led to higher microcystin concentrations [16].…”

Section: Environmental E¡ects On Toxin Productionmentioning

confidence: 99%

Ecological and molecular investigations of cyanotoxin production

Kaebernick

2001

FEMS Microbiology Ecology

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Iron-stimulated toxin production in Microcystis aeruginosa

Abstract: Nitrate-and phosphate-limited conditions had no effect on toxin production by Microcystis aeruginosa. In contrast, iron-limited conditions influenced toxin production by M. aeruginosa, and iron uptake was light dependent. A model for production of toxin by M. aeruginosa is proposed.

Cited by 234 publications

References 16 publications

Iron uptake and toxin synthesis in the bloom‐forming Microcystis aeruginosa under iron limitation

Iron uptake and toxin synthesis in the bloom‐forming Microcystis aeruginosa under iron limitation

Experimental iron amendment suppresses toxic cyanobacteria in a hypereutrophic lake

Ecological and molecular investigations of cyanotoxin production

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