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Abstract

We determined the patterns of occurrence of carotenoids and mycosporine-like amino acid compounds among 21 cyanobacterial isolates, variously ascribed to the genus Microcoleus, and used them as chemotaxonomical markers. All strains fitting the morphological and ecological description of M. chthonoplastes had a remarkably similar pattern of carotenoids and mycosporine-like amino acids (MAAs), regardless of their geographical origin. This supports the notion that these isolates represent a phylogenetically coherent group. However, small variations in the sugar moiety of their myxoxanthophylls and the occurrence of novel mycosporine-like amino acid compounds indicate some degree of either biogeographical or ecotypic diversification. The M. chthonoplastes-group of strains could easily be differentiated on the basis of the presence of the carotenoids echinenone, isozeaxanthin, zeaxanthin and various MAAs from all other isolates fitting the morphological and ecological descriptions of M. sociatus, M. paludosus, and M. lacustris, as well as other strains of uncertain affiliation, which have been assigned to Microcoleus in the literature. Our study demonstrates the applicability of the chemotaxonomy with carotenoids and mycosporines in solving problematic questions in low-rank cyanobacterial systematics.