ORIGINAL ARTICLE Phylogenetic comparison among the heterocystous cyanobacteria based on a polyphasic approach Arun Kumar Mishra & Ekta Shukla & Satya Shila Singh Received: 5 November 2011 / Accepted: 3 January 2012 # Springer-Verlag 2012 Abstract Phylogenetic comparison has been done among the selected heterocystous cyanobacteria belonging to the sections IVand V. The hierarchical cluster analysis based on antibiotics sensitivity showed a distant relationship between the members of Nostocales and Stigonematales. Thus, multiple antibiotic resistance pattern used as marker provide easy, fast, and reliable method for strain discrimination and genetic variabil- ity. However, morphological, physiological (both based on principal component analysis) and biochemical analysis grouped true branching cyanobacteria along with the mem- bers of section IV. Molecular analysis based on 16S rRNA gene sequences revealed that Hapalosiphon welwitschii and Westiellopsis sp. were grouped in cluster I whereas Scytonema bohnerii, a false branching genera showed a close proximity with Calothrix brevissima in cluster II. Cluster III of clade 2 included Nostoc calcicola and Anabaena oryzae which proved the heterogeneity at the generic level. Cluster IV the largest group of clade 2 based on 16S rRNA gene sequences includes six strains of the genera Nostoc, Anabaena, and Cylindrospermum showing ambiguous evolutionary relation- ship. In cluster IV, Anabaena sp. and Anabaena doliolum were phylogenetically linked by sharing 99% sequence similarity. Probably, they were of the same genetic makeup but appear differently under the diverse physiological conditions. Section IV showed polyphyletic origin whereas section V showed monophyletic origin. Results suggested that either morpho- logical or physiological or biochemical or molecular attribute is not sufficient to provide true diversity and phylogeny of the cyanobacteria at the generic level and thus, a polyphasic approach would be more appropriate and reliable. Keywords Cyanobacteria . Heterocyst . Polyphasic approach . Protein profiling . 16S rRNA Introduction Cyanobacteria, the oxygenic photosynthetic prokaryotes, occur both in free-living and symbiotic conditions. They show remarkable degree of morphological, developmental, and physiological diversity. Traditionally, the taxonomy of the cyanobacteria has been formulated under the Interna- tional Code of Botanical Nomenclature based on phenotypic characters such as morphology of the filament, vegetative cells, heterocyst and akinetes, form of the colony, shape of the terminal cells, presence or absence of sheath, gas vesicles, and other characters which lead to misidentifica- tion of phylogenetically coherent taxa (Desikachary 1959; Komárek and Anagnostidis 1989). Nowadays, cyanobacte- rial taxonomy based on morphology has been the matter of debate because there is always a possibility that different forms of single species may carry different specific epithets or strains of the same morphophyte and which may be distinguished by the different name as a consequence of Handling Editor: Peter Nick A. K. Mishra (*) : E. Shukla Laboratory of Microbial genetics, Department of Botany, Banaras Hindu University, Varanasi 221005, India e-mail: akmishraau@rediffmail.com A. K. Mishra e-mail: akmishraau@hotmail.com Present Address: S. S. Singh Guru Ghasidas Vishwavidyalaya, Bilaspur, Chhattisgarh, India Protoplasma DOI 10.1007/s00709-012-0375-9