Abstract
Recently, the green synthesis of nanoparticles has gained considerable attention due to its benefits such as cost efficiency, simplicity, eco-friendly nature, biocompatibility and broad applications over conventional chemical and physical techniques. In this context twenty actinobacteria were isolated from the rhizospheric soil of wild carrot and screened for their pigment producing ability. These isolates belong to the genus Streptomyces (58%), followed by Streptosporangium sp. (19%), Nocardia sp. (11%), Actinomadura sp. (8%), and Micromonospora sp. (4%). The most promising isolate (NS-05) producing the pink pigment has been taken for the synthesis of silver nanoparticles. The isolate NS-05 was identified as Streptomyces sp. based on cultural characteristics and 16S rDNA sequence analysis. It was most closely related with type strain Streptomyces fulvissimus DSM 40593T, S. microflavus NBRC13062T, S. setonii NRRL ISP-5322T, S. anulatus RRL B-2000T with a sequence similarity of 95.6% which shows that it may belong to novel species of Streptomyces. The bio-pigment assisted synthesized nanoparticles were characterized using UV-Vis, FTIR and Scanning electron microscopy studies. The average size of synthesized silver nanoparticles was 42.5nm and has λ max at 433 nm. The synthesized nanoparticles showed promising activity against major pathogens like Staphylococcus aureus MTCC 2940, Bacillus subtilis MTCC 441 Salmonella typhi, Proteus vulgaris MTCC 6380, Escherichia coli MTCC 739. The findings of present research are promising, and this pigment can also be used for the green synthesis of other nanoparticles.
Highlights
Actinobacteria are Gram-positive, filamentous bacteria widely distributed in water, soil, and other natural ecosystems
The isolate NS-05 was identified as Streptomyces sp. based on cultural characteristics and 16S rDNA sequence analysis. It was most closely related with type strain Streptomyces fulvissimus DSM 40593T, S. microflavus NBRC13062T, S. setonii NRRL ISP-5322T, S. anulatus RRL B-2000T with a sequence similarity of 95.6% which shows that it may belong to novel species of Streptomyces
The findings of present research are promising, and this pigment can be used for the green synthesis of other nanoparticles
Summary
Actinobacteria are Gram-positive, filamentous bacteria widely distributed in water, soil, and other natural ecosystems. Antibiotics produced by the actinobacteria make 80% of the known antibiotics (Waksman, 1961). The red pigment synthesized by certain bacteria including actinobacteria, Serratia marsences and Streptomyces and this pigment belong to the family called prodigosin (Khanafari et al, 2006). The presence of active chemicals in the extracted pigment and cells are responsible for the complex bio-reduction reaction process (Sadeghi et al, 2015; Baraka et al, 2017; John et al, 2020). Many researchers have synthesized nanoparticles based on chemical, physical and biological method (San Diego et al, 2020). In this context, we undertook the present study to isolate the pigment-producing actinobacteria and synthesis of pigment assisted nanoparticles and study its biological activity
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