Research
| Title： | Mutual Dependence of Nitrogen and Phosphorus as Key Nutrient Elements: One Facilitates Dolichospermum flos-aquae to Overcome the Limitations of the Other |
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| First author： | Wang, Siyang; Xiao, Jian; Wan, Lingling; Zhou, Zijun; Wang, Zhicong; Song, Chunlei; Zhou, Yiyong; Cao, Xiuyun |
| Journal： | ENVIRONMENTAL SCIENCE & TECHNOLOGY |
| Years： | 2018 |
| DOI： | 10.1021/acs.est.7b04992 |
| Abstract： | 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. N-2 fixation in terms of heterocyst density, nitrogenase activity and nif H expression increased significantly in P-replete cultures, suggesting that P enrichment facilitates N-2 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. |
