Abstract
Actinobacteria are the major source of bioactive natural products that find their value in research and drug discovery programmes. Antimicrobial resistance and the resulting high demand for novel antibiotics underscore the need for exploring novel sources of these bacteria endowed with biosynthetic potential. Intertidal ecosystems endure regular periods of immersion and emersion, and represent an untapped source of Actinobacteria. In this study, we studied the diversity and biosynthetic potential of cultivable Actinobacteria from intertidal sediments of Diu Island in the Arabian Sea. A total of 148 Actinobacteria were selectively isolated using a stamping method with eight isolation media. Isolates were grouped into OTUs based on their 16S rRNA gene sequence, and categorized within actinobacterial families such as Glycomycetaceae, Micromonosporaceae, Nocardiaceae, Nocardiopsaceae, Pseudonocardiaceae, Streptomycetaceae, and Thermomonosporaceae. The biosynthetic potential of the Actinobacteria, necessary for secondary metabolite biosynthesis, was screened and confirmed by extensive fingerprinting approaches based on genes coding for polyketide synthases and nonribosomal peptide synthetases. The observed biosynthetic potential was correlated with the antibacterial activity exhibited by these isolates in laboratory conditions. Ultimately, the results demonstrate that intertidal sediment is a rich source of diverse cultivable Actinobacteria with high potential to synthesize novel bioactive compounds in their genomes.
Highlights
Infectious diseases and multidrug resistance of clinically relevant pathogens are threatening global human healthcare systems[1]
Most of the actinobacterial colonies were visible by the second week of incubation; some took as long as 5 weeks to appear on isolation agar
Marine Actinobacteria have remarkable ability to produce a wealth of metabolites with substantial structural complexity and exceptional biological activity
Summary
Infectious diseases and multidrug resistance of clinically relevant pathogens are threatening global human healthcare systems[1]. Marine Actinobacteria evolved with unique physiological, chemical, and structural features that enable them to survive under the varying pressure, salinity, and temperature occurring in marine ecosystems[24,25,26] Such marine organisms are further endowed with the ability to produce novel molecules with interesting therapeutic applications not observed in their terrestrial counterparts, which is evident from various findings reporting the production of diverse bioactive compounds[20,21,22,23,24,25,26,27]. Diu (20.71°N 70.98°E) is a small island in the Arabian Sea near the Saurashtra Peninsula of Gujarat (India) covering an area of 38.8 km[2] Intertidal regions of this island would be a potential source of unique and diverse microorganisms; there is no report on the isolation and characterization of Actinobacteria from this region. The results illustrate the high levels of diversity and biosynthetic potential dictated in terms of genomic fingerprints
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