Underestimated biodiversity as a major explanation for the perceived rich secondary metabolite capacity of the cyanobacterial genus Lyngbya.

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Marine cyanobacteria are prolific producers of bioactive secondary metabolites responsible for harmful algal blooms as well as rich sources of promising biomedical lead compounds. The current study focused on obtaining a clearer understanding of the remarkable chemical richness of the cyanobacterial genus Lyngbya. Specimens of Lyngbya from various environmental habitats around Curaçao were analysed for their capacity to produce secondary metabolites by genetic screening of their biosynthetic pathways. The presence of biosynthetic pathways was compared with the production of corresponding metabolites by LC-ESI-MS² and MALDI-TOF-MS. The comparison of biosynthetic capacity and actual metabolite production revealed no evidence of genetic silencing in response to environmental conditions. On a cellular level, the metabolic origin of the detected metabolites was pinpointed to the cyanobacteria, rather than the sheath-associated heterotrophic bacteria, by MALDI-TOF-MS and multiple displacement amplification of single cells. Finally, the traditional morphology-based taxonomic identifications of these Lyngbya populations were combined with their phylogenetic relationships. As a result, polyphyly of morphologically similar cyanobacteria was identified as the major explanation for the perceived chemical richness of the genus Lyngbya, a result which further underscores the need to revise the taxonomy of this group of biomedically important cyanobacteria.