Four chemotypes of the terrestrial cyanobacterium Nostoc commune characterized by differences in the mycosporine-like amino acids

The cyanobacterium Nostoc commune is adapted to terrestrial environments and has a cosmopolitan distribution. Four genotypes of N. commune can be identified based on differences in their 16S rRNA genes, and these genotypes are distributed throughout Japan without regional specificity. Mycosporine-like amino acids (MAAs) are UV-absorbing pigments, and novel glycosylated MAA derivatives with radical scavenging activities have been identified in N. commune. In this study, we investigated the consistency of the relationship between MAA compositions and N. commune genotypes. The MAA compositions were different in a genotype-specific manner, suggesting that the types of MAA derivatives can feasibly be used as chemotaxonomic markers to characterize N. commune. The novel 756-Da MAA, which was identified as an aglycone of the 1050-Da MAA and named nostoc-756, occurred in genotype C of N. commune. Nostoc-756 functioned as a radical scavenger in vitro. In conclusion, N. commune is classified into four groups representing genetically different chemotypes, namely, the arabinose-bound porphyra-334 producer (chemotype A), the glycosylated nostoc-756 producer (chemotype B), the nostoc-756 producer (chemotype C) and the glycosylated palythine-threonine producer (chemotype D). Either the molecular taxonomical method or chemical analysis of a characteristic secondary metabolite is sufficient to identify the types of N. commune; however, there are no obvious ecophysiological differences that allow us to distinguish them.