Antibacterial and Antifungal Activities of Cyanobacterial Strains Isolated from Hot Springs in Oman

Abstract

In this study, cyanobacterial microbial mats from five hot springs in Oman, namely Al Kasfah Rustaq, Al Thwara Nakhl, Al–Ali Hammam, Gala and Bowsher, were characterized using direct microscopy. Nine monoclonal cyanobacterial cultures were obtained and their extracts in butanol, dichloromethane (DCM) and hexane were screened for antibacterial and antifungal activities. Direct microscopy revealed the presence of 12 different unicellular and filamentous morphotypes, with different distribution in the various mats. Temperature seems to be one of the most important parameters that accounts for the differences in cyanobacterial composition of the mats. Cells of the nine isolates and their aqueous supernatants were subsequently extracted with butanol, DCM and hexane. Dried extracts were tested against nine bacterial (i.e. gram +ve Staphylococcus aureus, Bacillus subtilis and gram –ve, Escherichia coli, Klebsiella pneumoniae, Salmonella choleraesuis, S. enterica, Psuedomonas aeruginosa, Providencia stuartii, and Acinetobacter calcoaceticus) and two fungal pathogens (Rhizoctonia solani and Pythium sp.). All isolates exhibited antibacterial and antifungal activities, which depended mainly on the type of cyanobacterial culture, type of solvent used and the pathogen tested. The highest antibacterial activity was observed in Phormidium species, and butanol was found to be the most appropriate solvent to extract bioactivity from these cyanobacterial species. The results of this study suggest that thermal springs in Oman harbor diverse types of cyanobacteria, which may constitute an important source of antibacterial and antifungal compounds. Further investigation is needed to purify these compounds and find their chemical compositions and modes of action.

Hot Springs Cyanobacteria Endowed with Biological Activities for Cosmetic Applications: Evaluation of On-Site Collected Communities and Isolated Strains

“…Additionally, inhibition of quorum sensing was observed in extracts from three of the springs, whereas anti-diatom activity from all four suggested the production of metabolites to regulate interactions among different microbial groups. In contrast to what was observed in our work, cyanobacterial strains isolated from the four hot springs showed a wider and more potent antibacterial activity compared to microbial mats, besides showing antifungal activity [63]. Antimicrobial properties of strains isolated from hot springs, also for nonphotosynthetic microorganisms, have been reported.…”

Sub-Aerial Cyanobacteria: A Survey of Research with Antimicrobial Properties for Pharmaceutical Approaches

“…Literature stresses isolation and identification of Cyanobacteria from a diverse environment with bioactivities, but only few research has focused on a variety of bioactive compounds produced by Cyanobacteria after analysis of a great number of marines [41][42][43], freshwater [44][45][46], terrestrial [47,48], and hot spring [49,50]. Cyanobacterial natural products still seem to prevail followed at much lesser proportions by alkaloids, aromatic compounds, cyclic depsipeptides, cyclic peptides, cyclic peptide, cyclophane, fatty acids, linear peptides, lipopeptides, nucleosides, phenols, macrolides, polyketides, polyphenyl ethers, porphinoids and terpenoids [51].…”