Molecular approaches towards assessment of cyanobacterial biodiversity

Abstract

Cyanobacteria, a diverse group of photosynthetic prokaryotes, often play central roles in carbon and nitrogen assimilation which makes their environment productive. Despite their significant agronomic values, biodiversity assessment and conservation of these important microbes have not been given much attention by researchers. This review tries to bring together the important aspects of molecular approaches being used for cyanobacterial biodiversity assessment. Molecular approaches have been divided into 2 classes: PCR independent and PCR based approaches. While the former includes guanine plus cytosine (G+C) content, nucleic acid re-association and hybridization and DNA microarrays, the latter basically uses DNA cloning and sequencing, DGGE (denaturing gradient gel electrophoresis), TGGE (temperature gradient gel electrophoresis), SSCP (single strand conformation polymorphism), RFLP (restriction fragment length polymorphism), ARDRA (amplified ribosomal DNA restriction analysis), T-RFLP (terminal restriction fragment length polymorphism), RISA (ribosomal intergenic spacer analysis), ARISA (automated ribosomal intergenic spacer analysis) and RAPD (random amplified polymorphic DNA). Molecular assessment of cyanobacterial biodiversity frequently uses markers like 16S rDNA, phycocyanin locus, nif gene, rpo gene, ITS region etc. This article examines and compares various conventional and modern methods and their short comings, if any. It attempts to provide a general overview of biodiversity assessment, molecular techniques and markers used for biodiversity assessment and also recommends combinatorial approach with different molecular markers. It is likely to improve the degree of resolution and provide as possible the broadest picture and indepth information about biodiversity documentation. Key words: Cyanobacteria, biodiversity, molecular approaches, molecular markers, DGGE, TGGE, SSCP, RFLP, ARDRA, T-RFLP, RISA, ARISA, RAPD, 16S rDNA, phycocyanin locus, nif gene, rpo gene.