The effects of exogenous amino acids on production of microcystin variants in Microcystis aeruginosa

The effects of exogenous amino acids on production of microcystin variants in Microcystis aeruginosa

•Leu and Phe clearly inhibited the growth and MCs production in M. aeruginosa.•Leu and Phe increased the abundance of MCs variants with relevant structures.•Quotas of Chl-a, PC, and APC in M. aeruginosa reduced when exposed to amino acids.•The expression of pipX was upregulated while mcyD was downre...

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Published in:Aquatic toxicology Vol. 259; p. 106525
Main Authors: Guo, Yaxin, Zhao, Xiating, Yao, Zongcheng, Qian, Zongyao, Wang, Yuting, Xian, Qiming
Format: Journal Article
Language:English
Published: Netherlands Elsevier B.V 01-06-2023
Subjects:
Amino acids
Amino Acids - metabolism
Arginine - metabolism
Chlorophyll A - metabolism
Glutamic Acid - metabolism
Leucine - pharmacology
MCs variants
Microcystins - toxicity
Microcystis
Microcystis aeruginosa
Nitrates - pharmacology
Nitrogen - metabolism
Phenylalanine - metabolism
Phenylalanine - pharmacology
Water Pollutants, Chemical - toxicity
Amino acids
Microcystis aeruginosa
Nitrogen metabolism
MCs variants
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Summary:•Leu and Phe clearly inhibited the growth and MCs production in M. aeruginosa.•Leu and Phe increased the abundance of MCs variants with relevant structures.•Quotas of Chl-a, PC, and APC in M. aeruginosa reduced when exposed to amino acids.•The expression of pipX was upregulated while mcyD was downregulated when exposed to amino acids. Dissolved free amino acids are a significant component of dissolved organic nitrogen (DON) in natural waterbodies. The effects of four amino acids (glutamic acid, phenylalanine, leucine, and arginine) on the growth and microcystins (MCs) production of Microcystis aeruginosa were studied in batch culture. The profiles of five MCs variants and the expression levels of target genes involved in MCs biosynthesis and nitrogen metabolism were measured. When amino acids were used as the sole nitrogen source instead of nitrate at different levels (0.5, 2.0 and 8.0 mg/L based on N) in BG-11 medium, algal cell growth and intracellular MCs quotas were inhibited slightly by the treatments with glutamic acid and arginine. The treatments with phenylalanine and leucine, on the other hand, had a strong inhibitory effect on algal cell growth and MCs production. Moreover, the concentrations of Chlorophyll a, phycocyanin and allophycocyanin in cells cultured in glutamic acid, leucine and phenylalanine were lower than those in the control group with nitrate as nitrogen source. The existence of leucine or phenylalanine can lead to a significant increase in the relative abundance of MCs variants structured with the corresponding amino acids. The expression of microcystin-producing gene mcyD was downregulated while the gene pipX associated with nitrogen metabolism was upregulated during the cultivation of M. aeruginosa with amino acids as sole nitrogen source. M. aeruginosa undergoes significant alterations due to exogenous amino acids and exhibits advanced strategies for MCs production.
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content type line 23
ISSN:0166-445X
1879-1514
DOI:10.1016/j.aquatox.2023.106525