Taxonomic diversity, antimicrobial potential and metabolite profiling of aquatic actinobacteria from Kallar Kahar Lake, Pakistan

As the discovery of novel antibiotics and other biotechnologically useful compounds has been exhausted so molecular characterization of actinomycetes from less explored habitats may be an alternate solution to this challenge. The aim of this study was to explore the actinobacterial diversity of the saline lake, situated in the salt range, Punjab, Pakistan and to screen them for antagonistic activities against multi drug resistant pathogens and to characterize the bioactive metabolites produced by them. A total of seventy strains of actinomycetes were isolated from lake samples, out of them only forty bioactive strains were selected for further characterization on the basis of their preliminary antimicrobial activities. The isolated actinobacterial strains showed an optimum growth at alkaline pH (9.0-9.5). The taxonomic analysis revealed that these isolates were closely affiliated with the genus Streptomyces (62.5%), Lentzae (6.25%), Pseudonocardia (6.25%), Lechevalieria (6.25%) and Nocardiopsis (12.5%). Most of the isolated strains exhibited strong inhibition against a broad range of pathogenic test organisms. The partial purification and metabolite profiling using ultra performance liquid chomatography and mass spectrometric (UPLC-MS) analysis suggested the presence of a variety of bioactive compounds including totarol, kifunensine, talaromycin and clausine F. These results indicated that Kallar Kahar Lake harbors a significant diversity of actinobacterial strains which are able to produce a diverse range of biotechnologically and pharmaceutically potent compounds. Further studies related to the structure elucidation of secondary metabolites can lead to the discovery of new and useful drug candidates.