Description of Aliinostoc alkaliphilum sp. nov. (Nostocales, Cyanobacteria), a New Bioactive Metabolite-Producing Strain from Salina Verde (Pantanal, Brazil) and Taxonomic Distribution of Bioactive Metabolites in Nostoc and Nostoc-like Genera

Cyanobacteria are a group of oxygenic photosynthetic prokaryotes found in almost all habitats on earth including those characterized as extreme environments. It has been observed that the number of studies dealing with the biodiversity of extremophilic cyanobacteria is limited while studies exploring their bioactive potential are even scarcer. The taxonomy of three Nostoc-like cyanobacterial strains isolated from a shallow lake in Brazil was studied by applying a polyphasic approach. The bioactive potential of the strains was also evaluated using antimicrobial susceptibility testing. The metabolites present in the bioactive HPLC fractions were identified by UPLC/ESI/Q-TOF. Based on our phylogenetic inferences in combination with morphological and ecological information, we describe Aliinostoc alkaliphilum sp. nov., exhibiting antibacterial and antifungal activities. The main bioactive metabolite in all three strains was nocuolin A, which represents the first report of this metabolite in Aliinostoc. Our phylogenetic studies also revealed that many bioactive metabolite-producting strains that are currently assigned to Nostoc belong to other distinct evolutionary lineages. These findings highlight the importance of polyphasic approach studies in both cyanobacterial taxonomy and natural product discovery programs.