AUTHOR=Dholakiya Riddhi N. , Kumar Raghawendra , Mishra Avinash , Mody Kalpana H. , Jha Bhavanath 

TITLE=Antibacterial and Antioxidant Activities of Novel Actinobacteria Strain Isolated from Gulf of Khambhat, Gujarat

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.02420

DOI=10.3389/fmicb.2017.02420

ISSN=1664-302X

ABSTRACT=<p>Bacterial secondary metabolites possess a wide range of biologically active compounds including antibacterial and antioxidants. In this study, a Gram-positive novel marine <italic>Actinobacteria</italic> was isolated from sea sediment which showed 84% 16S rRNA gene sequence (KT588655) similarity with <italic>Streptomyces variabilis</italic> (EU841661) and designated as <italic>Streptomyces variabilis</italic> RD-5. The genus <italic>Streptomyces</italic> is considered as a promising source of bioactive secondary metabolites. The isolated novel bacterial strain was characterized by antibacterial characteristics and antioxidant activities. The BIOLOG based analysis suggested that <italic>S. variabilis</italic> RD-5 utilized a wide range of substrates compared to the reference strain. The result is further supported by statistical analysis such as AWCD (average well color development), heat-map and PCA (principal component analysis). The whole cell fatty acid profiling showed the dominance of iso/anteiso branched C15–C17 long chain fatty acids. The identified strain <italic>S. variabilis</italic> RD-5 exhibited a broad spectrum of antibacterial activities for the Gram-negative bacteria (<italic>Escherichia coli</italic> NCIM 2065, <italic>Shigella boydii</italic> NCIM, <italic>Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas</italic> sp. NCIM 2200 and <italic>Salmonella enteritidis</italic> NCIM), and Gram-positive bacteria (<italic>Bacillus subtilis</italic> NCIM 2920 and <italic>Staphylococcus aureus</italic> MTCC 96). Extract of <italic>S. variabilis</italic> strain RD-5 showed 82.86 and 89% of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and metal chelating activity, respectively, at 5.0 mg/mL. While H<sub>2</sub>O<sub>2</sub> scavenging activity was 74.5% at 0.05 mg/mL concentration. Furthermore, polyketide synthases (PKSs types I and II), an enzyme complex that produces polyketides, the encoding gene(s) detected in the strain RD-5 which may probably involve for the synthesis of antibacterial compound(s). In conclusion, a novel bacterial strain of <italic>Actinobacteria</italic>, isolated from the unexplored sea sediment of Alang, Gulf of Khambhat (Gujarat), India showed promising antibacterial activities. However, fractionation and further characterization of active compounds from <italic>S. variabilis</italic> RD-5 are needed for their optimum utilization toward antibacterial purposes.</p>