The Effects of Cyanobacterial Bloom Extracts on the Biomass, Chl-a, MC and Other Oligopeptides Contents in a Natural Planktothrix agardhii Population

Abstract

Blooms of the cyanobacterium Planktothrix agardhii are common in shallow, eutrophic freshwaters. P. agardhii may produce hepatotoxic microcystins (MCs) and many other bioactive secondary metabolites belonging mostly to non-ribosomal oligopeptides. The aim of this work was to study the effects of two extracts (Pa-A and Pa-B) of P. agardhii-predominated bloom samples with different oligopeptide profiles and high concentration of biogenic compounds on another natural P. agardhii population. We hypothesised that the P. agardhii biomass and content of oligopeptides in P. agardhii is shaped in a different manner by diverse mixtures of metabolites of different P. agardhii-dominated cyanobacterial assemblages. For this purpose, the biomass, chlorophyll a and oligopeptides content in the treated P. agardhii were measured. Seven-day microcosm experiments with four concentrations of the extracts Pa-A and Pa-B were carried out. Generally, aeruginosins (AERs), cyanopeptolins (CPs) and anabaenopeptins (APs) were the most numerous peptides; however, only 16% of them were common for both extracts. The addition of the extracts resulted in similar effects on P. agardhii: an increase in biomass, Chl-a and MC content in the exposed P. agardhii as well as changes in its oligopeptide profile were observed. MCs present in the extracts did not inhibit accumulation of P. agardhii biomass, and did not have any negative effect on MC and Chl-a content. No evidence for bioaccumulation of dissolved peptides in the P. agardhii exposed was found. As the two tested extracts differed considerably in oligopeptide composition, but contained similar high concentrations of nutrients, it seems that biogenic compounds, not oligopeptides themselves, positively influenced the mixed natural P. agardhii population.

Competitive interactions as a mechanism for chemical diversity maintenance in Nodularia spumigena

“…Therefore, the correlations between NRPs from different classes, particularly with NODs, cannot be related to the interlinked metabolic pathways. These correlations indicate that some NRPs may have complementary functions in the cyanobacterium, as previously suggested 31 , 52 . Further studies on the mechanisms behind the synchronized dynamics of such NRPs are needed.…”

“…M. aeruginosa PCC 7806 and PCC 9432) 31 , 51 . Also, Planktothrix agardhii exposed to two distinct cell extracts of bloom samples predominated by P. agardii (95% total biomass) had its NRPs levels both higher or lower than in the controls (monocultures), depending on the cell extract 52 . It is important to note that each cell extract consists of P. agardii strains of several chemotypes of different NRP profiles 52 , 53 .…”

“…Also, Planktothrix agardhii exposed to two distinct cell extracts of bloom samples predominated by P. agardii (95% total biomass) had its NRPs levels both higher or lower than in the controls (monocultures), depending on the cell extract 52 . It is important to note that each cell extract consists of P. agardii strains of several chemotypes of different NRP profiles 52 , 53 . Therefore, it can be concluded that cyanobacteria intraspecific interactions promote a more chemical diverse population; co-existing strains of more distinct chemotypes produce more NRPs than co-existing strains of similar chemotypes.…”

Interplay of Nutrients, Temperature, and Competition of Native and Alien Cyanobacteria Species Growth and Cyanotoxin Production in Temperate Lakes

“…A high variety of the MCs and bioactive non-ribosomal peptides was detected in scum samples of P. agardhii [ 48 ]. The current experimental study demonstrated that the toxic P. agardhii strain was able to produce three different variants of the MCs, and the shift in the proportion of MCs variants under varied nutrient conditions was not observed.…”

Revealing Cryptic Changes of Cyanobacterial Community Structure in Two Eutrophic Lakes Using eDNA Sequencing

“…In subtropical and temperate lakes, Dolichospermum and Aphanizomenon usually become dominant when the abundance of Microcystis decreases in winter and spring [ 12 , 13 , 14 ]. However, Raphidiopsis forms perennial blooms in many tropical and subtropical lakes [ 15 ], whereas Planktothrix can be exclusively dominant in temperate lakes with relatively low water temperatures [ 16 , 17 ]. Therefore, temperature is a critical factor affecting the composition of the cyanobacterial community.…”