LAUSR

Abstract Actinomycetes are Gram-positive, filamentous bacteria with high guanine and cytosine content. They are facultative anaerobes, known for their ability to produce secondary metabolites. In this study, actinomycetes were isolated from saline and alkaline soils of the Rann of Kutch (RoK), Gujarat, India. The isolates were characterized based on their colony morphology, staining reactions, enzymatic activities, and molecular features. Specific analyses included melanin pigment production, nitrate reductase activity, and antibiotic potential. Additionally, the influence of pH, temperature, and nutrient media on their growth was evaluated. Soil samples were collected from 10 different sites, six in the Little Rann of Kutch and four in the Great Rann of Kutch. A total of 26 distinct actinomycete isolates were obtained, with 13 isolates from each subregion. Among them, 16 isolates (61.5%) showed positive lipase activity on tributyrin agar, and 13 isolates (50%) produced melanin pigments. Optimal growth temperature was 30 °C for 18 isolates (69.2%), and 40 °C for 8 isolates (30.8%). All isolates tolerated pH 7–9, with optimal growth observed at pH 8 (50%) and pH 9 (50%). Salt tolerance ranged from 0% to 10% NaCl, confirming their halotolerant and alkaliphilic nature. Antimicrobial screening revealed that 23 isolates (88.5%) exhibited activity against at least one test pathogen, and 4 isolates (15.4%) showed anti-MRSA activity. The most potent isolate, GR-ADE-1, exhibited inhibition zones up to 40 mm against B. subtilis and 30 mm against E. coli. Three highly active strains were identified by 16S rRNA sequencing as Nocardiopsis alba, Streptomyces tendae, and Streptomyces rochei. This study highlights the antimicrobial potential and physiological resilience of actinobacteria from an extreme desert ecosystem and supports their application in bioprospecting for novel therapeutics.