The marine environment harbour diverse microbial communities. Isolation of actinobacteria from such habitats would facilitate the exploration of new bioactive compounds with novel molecular structures. The diversity of seaweed associated actinobacteria and their metabolites are relatively less explored. Hence, the present study is an attempt to cultivate and characterize the actinobacteria population associated with seaweeds, Codium dwarkense and Sargassum cinereum, collected from the Veraval coastal area, Gujarat, India. For the cultivation, various growth media, including the International Streptomyces Project (ISP) media, Nutrient agar (NA), Starch agar (SA), Starch casein agar (SCA), Actinomycetes isolation agar (AIA) were prepared using artificial seawater. The seaweed sample Sargassum cinereum showed the highest colony forming units (CFU) count on SA, ISP 6, and ISP 1 media plates, while the least CFU was observed on ISP 5, ISP 3, and AIA media plates. The seaweed sample, Codium dwarkense, yielded the highest CFU count on ISP 4, ISP 2, and ISP 7 media followed by ISP6, ISP3, and NA media. In comparison, from the seawater sample, the highest CFU count was observed in NA, ISP 6, and SA media. To adjust the high colony-forming units, various dilution strategies were applied. The plates with 0.1 dilutions resulted in crowded growth while very little or no growth was observed with 0.001 dilutions. Various actino morphotypes were observed associated with both the seaweeds as both seaweeds contain different carbon and nitrogen sources. The majority of morphotypes displayed a chalky appearance with varying pigments. Microscopic observation of morphotypes revealed Gram positive nature with filamentous morphology. Thus, the study highlights the isolation strategies and characterization of cultivable actinobacteria associated with seaweed and seawater from the Veraval coastline. 

Seaweeds, marine actinobacteria, pigmentation, diversity, distribution