Chemically mediated interactions between Microcystis and Planktothrix: impact on their growth, morphology and metabolic profiles

Abstract

Summary Freshwater cyanobacteria are known for their ability to produce bioactive compounds, some of which have been described as allelochemicals. Using a combined approach of co‐cultures and analyses of metabolic profiles, we investigated chemically mediated interactions between two cyanobacterial strains, Microcystis aeruginosa PCC 7806 and Planktothrix agardhii PCC 7805. More precisely, we evaluated changes in growth, morphology and metabolite production and release by both interacting species. Co‐culture of Microcystis with Planktothrix resulted in a reduction of the growth of Planktothrix together with a decrease of its trichome size and alterations in the morphology of its cells. The production of intracellular compounds by Planktothrix showed a slight decrease between monoculture and co‐culture conditions. Concerning Microcystis, the number of intracellular compounds was higher under co‐culture condition than under monoculture. Overall, Microcystis produced a lower number of intracellular compounds under monoculture than Planktothrix, and a higher number of intracellular compounds than Planktothrix under co‐culture condition. Our investigation did not allow us to identify specifically the compounds causing the observed physiological and morphological changes of Planktothrix cells. However, altogether, these results suggest that co‐culture induces specific compounds as a response by Microcystis to the presence of Planktothrix. Further studies should be undertaken for identification of such potential allelochemicals.

Insights into the Diversity of Secondary Metabolites of Planktothrix Using a Biphasic Approach Combining Global Genomics and Metabolomics

“…Other components of these molecular clusters correspond to ions presenting a mass match with other variants of aeruginosin previously described [41], and up to 58% of all these compounds may represent potential new aeruginosin variants. Interestingly, we noticed that several aeruginosin variants of the PCC 7805 (shown in dark green in Figure 4A) show characteristic isotopic pattern of mono- or di-chlorination, as recently illustrated for this strain by Briand and co-workers [53]. These observations are in agreement with genomic analysis that detects a non-heme iron O 2 -dependent halogenase, potentially involved in the halogenation of biosynthetic products in the aer cluster of this strain (Table 1).…”

The genetic and ecophysiological diversity of Microcystis

“…Large gaps in knowledge also remain on the functions of other secondary metabolites in Microcystis, but substantial evidence supports the hypothesis that they enhance its competitiveness through allelopathic interactions (Briand et al, 2016(Briand et al, , 2019Chia et al, 2018). These compounds can inhibit the photosynthetic capacity, growth, and regulatory processes of competitors or predators (Huisman et al, 2005;Chia et al, 2018).…”

Daphnia magna Exudates Impact Physiological and Metabolic Changes in Microcystis aeruginosa

“…Most reported studies on MC production explore how abiotic factors influence toxin production, while only a few studies aim to understand the impact of biotic factors (mainly phytoplankton competition and zooplankton grazing) as MCs triggers in Microcystis [26,35,36,37]. The role of cyanobacterial metabolites could be a defense mechanism against predators [38], where toxic species have a higher chance of survival compared to nontoxic species [1,39].…”