The terrestrial cyanobacterium Nostoc commune has a marked capacity against desiccation and can adapt to UV radiation stress as well as oxidative stress caused by UV radiation. The mechanism of adaptation to extreme conditions by this cyanobacterial species is thought to involve multiple processes and ability to produce mycosporine-like amino acids (MAAs) appears to be a required factor. In this study, three genotypes of N. commune colonies were studied and structurally novel MAAs were characterized. The genotype A of N. commune colony produces the pentose-bound porphyra-334 (478 Da), the hexose-bound porphyra-334 (508 Da) and the pentose-bound shinorine (464 Da). The genotype B of N. commune colony produces two types of hybrid-MAAs (880 Da and 1050 Da) linked to 2-O-(β-xylopyranosyl)-β-galactopyranoside. The genotype D of N. commune colony produces the hexose-bound palythine-threonine derivatives (450 Da and 612 Da) and the hexose-bound porphyra-334 (508 Da). Interestingly, all characterized MAAs are glycosylated and these glycosylated MAAs have radical scavenging activities in vitro. This glycosylation is unique to the terrestrial cyanobacterium N. commune. The glycosylation of porphyra-334, shinorine,palythine-threonine and hybrid-MAAs in N. commune suggests a unique adaptation for terrestrial environments that are drastically fluctuating in comparison to stable aquatic environments.
