Abstract
The taxonomic position of a filamentous, non-heterocystous, benthic cyanobacterium isolated from an industrial waste canal, Helwan district, Egypt was investigated using a polyphasic approach. The isolate possessed unique ultrastructural features including heavily-granulated cells except for the dome-shaped apical cell. There is also an observed longitudinal partitioning within the cell caused by membrane-like structure, thus dividing the cell into unequal sections. Also the presence of elemental sulfur globules, the presence of refractile stacked gas vesicle-like structures and convoluted irregularly-arranged thylakoids. Analysis of the ssu rDNA gene showed that the isolate was < 91% similar to other cyanobacteria sequences. The phylogenetic analysis showed the co-clustering of this isolate with other Phormidium isolates, thus implying its close phylogenetic relationship to this genus. To investigate other descriptive features of the isolate, fatty acid Composition was used as a chemotaxonomic marker. Saturated arachidic fatty acid was found in abundance followed by polyunsaturated fatty acids. Finally, the antimicrobial screening revealed the effectiveness of methanolic fractions against some pathogens. Collectively, the study shows that morphological similarities can mask internal heterogenieties and that the correct identification of organisms with unique characteristics gives us an insight into their metabolic features and would offer opportunities for future biotechnological exploitation.