Harmful algal bloom species Microcystis aeruginosa releases thiamin antivitamins to suppress competitors

ABSTRACT: In environmental ecosystems, vitamin concentrations are often exceedingly low and auxotrophy, or reliance on exogenous vitamin or vitamin precursors, is widespread. We show here that the widespread harmful algal bloom (HAB) species Microcystis aeruginosa, threatening freshwater aquatic ecosystems globally, releases a complex mixture of thiamin antivitamins, including bacimethrin and methoxythiamin, which induce thiamin deficiency in the model green alga Chlamydomonas reinhardtii. Putative biosynthetic genes for bacimethrin were upregulated in M. aeruginosa when grown in co-culture resulting in greater production of bacimethrin. Bacimethrin, methoxythiamin, oxidized forms of thiamin and methoxythiamin, and a novel structural homolog of bacimethrin were all found at elevated levels in the co-culture exometabolome extracts and were all inhibitory to the growth of C. reinhardtii individually at very low concentrations and as a mixture in culture medium extracts. The thiamin-requiring mutant C. reinhardtii, CC-25, was much more sensitive to bacimethrin and methoxythiamin than the wildtype. Thiamin addition largely rescued the inhibitory effects of exposure to antivitamins in both the wildtype and mutant strain. Finally, we determined that bacimethrin is present in aquatic environments and is elevated during Microcystis blooms. Thus, allelopathic suppression of competitors, particularly those that are auxotrophic for thiamin, by M. aeruginosa via the production of antivitamins in environments where thiamin availability is low, could help this species to become dominant and form blooms

INSTRUMENT(S): X500R QTOF

ORGANISM(S): Chlamydomonas Reinhardtii (ncbitaxon:3055) Microcystis Aeruginosa Niva-cya 118/2 (ncbitaxon:59621)

SUBMITTER: Beth Ahner  

PROVIDER: MSV000098018 | MassIVE | Wed May 28 10:12:00 BST 2025

REPOSITORIES: MassIVE