Changes in secondary metabolic profiles of Microcystis aeruginosa strains in response to intraspecific interactions

The cyanobacteria Microcystis proliferate in freshwater ecosystems and produce bioactive compounds including the harmful toxins microcystins (MC). These secondary metabolites play an important role in shaping community composition through biotic interactions although their role and mode of regulation are poorly understood. As natural cyanobacterial populations include producing and non-producing strains, we tested if the production of a range of peptides by coexisting cells could be regulated through intraspecific interactions. With an innovative co-culturing chamber together with advanced mass spectrometry (MS) techniques, we monitored the growth and compared the metabolic profiles of a MC-producing as well as two non-MC-producing Microcystis strains under mono- and co-culture conditions. In monocultures, these strains grew comparably; however, the non-MC-producing mutant produced higher concentrations of cyanopeptolins, aerucyclamides and aeruginosins than the wild type. Physiological responses to co-culturing were reflected in a quantitative change in the production of the major peptides. Using a MS/MS-based molecular networking approach, we identified new analogues of known classes of peptides as well as new compounds. This work provides new insights into the factors that regulate the production of MC and other secondary metabolites in cyanobacteria, and suggests interchangeable or complementary functions allowing bloom-forming cyanobacteria to efficiently colonize and dominate in fluctuating aquatic environments.

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Fig. S1. Identification of Cl2-aeruginosin 684. The WT and MT strains produced an aeruginosin with a mass of m/z 685 Da. This compound presented an isotopic pattern corresponding to ...
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Fig. S2. Identification of three new structural related compounds (P 612, 646 and 680). Partial mass spectrum of NT strain showing three molecular ion peaks (m/z 613, 647 and 681) with...
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Fig. S3. Identification of cyanopeptolins variants produced by WT and MT strains. MS/MS data of each variants: (A) Cya A, (B) Cya B, (C) Cya C, (D) Cya 895 and (E) Cya...
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Fig. S4. Identification of cyanopeptolins variants produced by NT strain. MS/MS data of each variant: (A) Cya 914, (B) Cya 948, (C) Cya 962, (D) Cya 964 and (E) Cya 978....
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Fig. S5. Relative concentrations given as a fold change over WT in monoculture of selected intracellular compounds for WT, MT and MT with MC-LR under mono- (WT/WT, MT/MT) and ...
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Fig. S6. Correlation between the relative concentrations of major compounds produced in the WT/MT experiment determined by the addition of internal standard and by the spectral ...
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Fig. S7. Over time diffusion of MC-LR through a 0.45 μm membrane in co-culture chambers.
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Briand Enora, Bormans Myriam, Gugger Muriel, Dorrestein Pieter C., Gerwick William H. (2016). Changes in secondary metabolic profiles of Microcystis aeruginosa strains in response to intraspecific interactions. Environmental Microbiology. 18 (2). 384-400.,

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