Cyanobacterial biofilms occurring on the exterior of three stone monuments at Santiniketan, India were analyzed. Species of Scytonema and Tolypothrix were the major components of these biofilms. Identification was obtained by morphometric procedures and 16S rRNA gene sequencing. Biofilms cultured for prolonged periods revealed the presence of several other cyanobacteria belonging to 14 different genera. Cyanobacteria on stone in the tropical environment of India formed a distinct cluster that was quite different from that of cyanobacteria reported for a similar substratum in temperate regions. Absorption spectra of the organisms from Santiniketan showed a high quantity of scytonemin, mycosporine-like amino acids, and carotenoids. All of the organisms survived in a desiccated state and rapidly revived after wetting. The organisms were heterocystous and nitrogenase activity was reactivated within 24 h of wetting by which time heterocysts in their filaments had also appeared.
Four strains of two species of Nostoc, N. commune (VB512188 and VB516200) and N. punctiforme (VB511286 and VB512190), isolated from the exterior of stone monuments and maintained in culture, showed very similar morphological features. Analysis of partial 16S rRNA gene sequences of these taxa with N. commune and N. punctiforme sequences from GenBank gave confusing results. Nostoc commune VB516200 and N. punctiforme VB511286 grouped together while the other two strains were placed in other clades. Phylogenetic analysis of an alignment including sequences of Nostoc and Desmonostoc species (N. commune, N. punctiforme and D. muscorum) from GenBank along with these four taxa, N. commune (VB512188 and VB516200) and N. punctiforme (VB511286) formed a distinct clade. However, the other strain of N. punctiforme (VB512190) clustered with sequences from Nostoc sp. from Spain and Australia and was quite distant from the other Indian samples. These results showed that identification of cyanobacterial species requires both morphological analysis in culture, and the use of molecular techniques.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.