Mutual Dependence of Nitrogen and Phosphorus as Key Nutrient Elements: One Facilitates Dolichospermum flos-aquae to Overcome the Limitations of the Other

Dolichospermum flos-aquae (formerly Anabaena flos-aquae) is a diazotrophic cyanobacterium causing harmful blooms worldwide, which is partly attributed to its capacity to compete for nitrogen (N) and phosphorus (P). Preventing the blooms by reducing P alone or both N and P has caused debate. To test...

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Bibliographic Details
Published in:Environmental science & technology 2018-05, Vol.52 (10), p.5653-5661
Main Authors: Wang, Siyang, Xiao, Jian, Wan, Lingling, Zhou, Zijun, Wang, Zhicong, Song, Chunlei, Zhou, Yiyong, Cao, Xiuyun
Format: Article
Language:English
Subjects:
Alkaline phosphatase
Anabaena
Cell culture
Cyanobacteria
Dependence
Dolichospermum
Eutrophication
Fixation
Fluorescence
Gene expression
Genes
NifH gene
Nitrogen
Nitrogen enrichment
Nitrogenase
Nitrogenation
Nutrients
Phosphates
Phosphomonoesters
Phosphorus
Physiological responses
Spectrophotometry
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Summary:Dolichospermum flos-aquae (formerly Anabaena flos-aquae) is a diazotrophic cyanobacterium causing harmful blooms worldwide, which is partly attributed to its capacity to compete for nitrogen (N) and phosphorus (P). Preventing the blooms by reducing P alone or both N and P has caused debate. To test the effects alone and together on the growth of cyanobacteria, we performed culture experiments in different eutrophication scenarios. N2 fixation in terms of heterocyst density, nitrogenase activity and nifH expression increased significantly in P-replete cultures, suggesting that P enrichment facilitates N2 fixation. Correspondingly, the expression of genes involved in P uptake, e.g., those involved in P-transport (pstS) and the hydrolysis of phosphomonoesters (phoD), was upregulated in P-deficient cultures. Interestingly, N addition enhanced not only the expression of these genes but also polyphosphate formation and alkaline phosphatase activity in P-deficient cultures relative to the P-replete cultures, as evidenced by qualitative (enzyme-labeled fluorescence) and quantitative (fluorogenic spectrophotometry) measurements. Furthermore, after N addition, cell activity and growth increased in the P-deficient cultures, underscoring the risk of N enrichment in P-limited systems. The eco-physiological responses shown here help further our understanding of the mechanism of N and P colimitation and underscore the importance of dual N and P reduction in controlling cyanobacterial blooms.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.7b04992