RESUMO
A freshwater dwelling cyanobacterium (strain MKW3) was isolated from a sample collected from a water logged sugarcane field located in Malkapur, Karad, Maharashtra, India, and was characterized using a polyphasic approach. In the 16S rRNA gene phylogenetic analysis, strain MKW3 clustered with two misidentified strains-Nostoc sp. CENA239 and Calothrix sp. NIES2100. The phylogenetically related members included strains identified as Nostoc, Aulosira, Calothrix, Tolypothrix, Camptylonemopsis and Microchaete. The phylogenetic and the morphological analysis of the strain MKW3 indicated that it does not belong to any of the above mentioned genera. Furthermore, the 16S-23S ITS secondary structure analysis provided clear evidence indicating that strain MKW3 is different from Nostoc sp. CENA239 and Calothrix sp. NIES2100. Based on the morphological, phylogenetic and 16S-23S ITS secondary structure analysis we describe our strain as Constrictifilum karadense gen. et sp. nov. in accordance with the International Code of Nomenclature for algae, fungi and plants.