Non-ribosomal peptides produced by Planktothrix agardhii from Siemianówka Dam Reservoir SDR (northeast Poland)

Abstract

Planktothtrix agardhii (Oscillatoriales) is a filamentous cyanobacterium, which frequently forms blooms in shallow, polymictic and eutrophicated waters. This species is also a rich source of unique linear and cyclic peptides. In the current study, the profile of the peptides in samples from the P. agardhii-dominated Siemianówka Dam Reservoir (SDR) (northeast Poland) was analyzed for four subsequent years (2009-2012). The LC-MS/MS analyses revealed the presence of 33 peptides. Twelve of the most abundant ones, including five microcystins, five anabaenopeptins, one aeruginosin and one planktocyclin, were present in all field samples collected during the study. The detection of different peptides in two P. agardhii isolates indicated that the SDR population was composed of several chemotypes, characterized by different peptide patterns. The total concentration of microcystins (MCs) positively correlated with the biomass of P. agardhii. Between subsequent years, the changes in the ratio of the total MCs concentration to the biomass of P. agardhii were noticed, but they were less than threefold. This is the first study on the production of different classes of non-ribosomal peptides by freshwater cyanobacteria in Poland.

Fig. 1

Chemical structure and enhanced ion product mass spectrum of anabaenopeptin A ([Phe-MeAla-HTyr-Val-Lys]CO-Tyr), with [M + H] ion at m/z 844, produced by Planktothrix agardhii from the SDR. The mass signals were assigned to the following fragments: 826 [M + H − H₂O], 816 [M + H − CO], 798 [M + H − H₂O − CO], 745 [M + H − Val], 681 [M + H − Tyr], 667 [M + H − Hty], 635 cyclo[Lys-Val-Hty-MeAla-Phe − H], 569 [M + H − (Hty − Val)], 551 [M + H − (Hty − Val) − H₂O], 405 [Htyr-Val-Lys + 2H], 362 [Ile-Hty-MeAla + H], 320 [(Lys-CO-Phe) + H], 136 Tyr-immonium ion, 107 [CH₂PhOH], 84 Lys-immonium ion, 58 MeAla-immonium ion

Fig. 2

Chemical structure and enhanced ion product mass spectrum of aeruginosin (Cl-Pla-Leu-(Xyl)Choi-Aeap), with [M + H] ion at 749, produced by Planktothrix agardhii from the SDR. The mass signals were assigned to the following fragments: 713 [M + H − Cl], 707 [M + H − CH₂N₂], 671 [M + H − CH₂N₂ − Cl], 593 [M + H − Cl − Pla fragment], 581 [M + H − Cl − Xyl], 461 [M + H − Cl − Pla fragment – Xyl], 454 [(Xyl)Choi-Aeap + 2H], 322 [Choi-Aeap + 2H], 305 [Choi-Aeap + H − NH₂], 280 [Choi-Aeap + 2H − CH₂N₂], 140 Choi-immonium ion, 122 Choi-immonium − H₂O