A molecular approach to cyanobacterial diversity in a rock-pool community involving gelatinous lichens and free-living Nostoc colonies

The cyanobacterial symbionts of Collema multipartitum and free-living Nostoc strains were studied by using the nucleotide sequence of the cyanobacterial tRNALeu(UAA) intron as a genetic marker. Biological specimens were collected from a series of interconnected depressions on a limestone pavement in western Ireland. In this material, free-living and lichenised Nostoc strains could be distinguished on the basis of the first variable region of the tRNALeu(UAA) intron. All the variable stem-loops had a similar heptanucleotide repeat motif, but lichenised and free-living strains differed in the number of repeats and in the presence/absence of additional sequences interrupting a single repeat. The results indicate that some filamentous cyanobacteria in rock-pool communities can be rapidly identified by using this molecular marker. The method could prove useful in ecological and environmental studies.