Journal of Applied Biology & Biotechnology Vol. 8(04), pp. 1-6, July-Aug, 2020 Available online at http://www.jabonline.in DOI: 10.7324/JABB.2020.80401 Efficacy of antibiotic sensitivity and antimicrobial activity of Streptomyces cinereoruber RSA-14 isolated from rhizosphere soil of Alternanthera sessilis (L.) R. Br. ex DC Sreenivasa Nayaka * , Halaswamy Hiremath, Bidhayak Chakraborty, Pallavi Sathyanarayan Swamy, Dhanyakumara Shivapoojar Basavarajappa, Shashiraj Kareyallappa Nagaraja, Muthuraj Rudrappa, Meghashyama Prabhakara Bhat, Dattatraya Airodagi, Meenakshi Shivanandagouda Murigennavar P.G. Department of Studies in Botany, Karnatak University, Dharwad, Karnataka 580003, India. ARTICLE INFO Article history: Received on: January 05, 2020 Accepted on: March 28, 2020 Available online: July 30, 2020 Key words: Alternanthera sessilis, rhizosphere soil, antibiotic, Streptomyces cinereoruber. ABSTRACT The search for novel antibiotics is of immense importance in research areas around the world for agricultural, pharmaceutical, and industrial applications. The Streptomyces species are widely used as an important biological tool for the production of a wide range of novel secondary metabolites. In the present study, isolated strain RSA-14 from rhizosphere soil of Alternanthera sessilis was subjected to morphological, physiological, biochemical and 16S rRNA gene sequence analysis. The isolated RSA-14 was analyzed for antimicrobial activities by cross streak method and exhibited a broad spectrum of antimicrobial activity against test pathogens. The isolate was tested for the ability to grow in the presence of antibiotics, such as penicillin, streptomycin, chloramphenicol, gentamycin, and tetracycline and resistant to only two antibiotics, and sensitive to others. The 16S ribosomal RNA gene sequencing and analysis of the phylogenetic tree showed 100% sequence similarity with Streptomyces cinereoruber strain P.B.373. 1. INTRODUCTION Actinomycetes are the most widely dispersed group of microorganisms in nature and widely distributed in soil, water, and affiliation with plants. Actinomycetes are Gram-positive microorganism allotted shape of branching hyphae with high G+C content material in their genes along with severe metabolic possibilities [1,2]. Actinomycetes preserve a distinguished purpose applications range in screening programs due to their diversity in the production of novel antibiotics of pharmaceutical interest. The rhizosphere is the narrow region influenced by plant roots and is a hot spot for numerous organisms, such as bacteria, fungi, and algae. Rhizosphere organisms that have been well studied for their really helpful effects on plant increase and health are the nitrogen- fixing bacteria, mycorrhizal fungi, plant growth-promoting rhizobacteria, bio-control microorganisms, mycoparasitic fungi, and protozoa [3]. Actinomycetes are current appreciably in the plant rhizosphere soil and produce a sturdy antimicrobial potential of pathogenic microorganisms, saprophytic in nature of plant amplify promoters and quite a number of agro-active compounds [4]. The best- known Actinomycetes in the soil are the genus Streptomyces, although others like Norcardia, Microbispora, Micromonospora, Actinoplanes, and Streptosporangium have additionally been isolated from soil [5]. Streptomyces is the biggest genus of Actinobacteria, out of 500 species; the Streptomyces species are aerobic, spore formers with DNA affluent and large branching substrate, aerial mycelia, and widely dispersed in soil [6]. They have been diagnosed as a prolific supply of bioactive microbial metabolites as they produce 75% of biotic active compounds. One of the first antibiotics used was streptomycin produced through the ability of Streptomyces griseus [7]. Nocardia species are a part of the soil microflora and play a feature in the turnover of organic matter; there is moreover proof that some strains produce secondary metabolites of attainable industrial purpose [8]. *Corresponding Author Sreenivasa Nayaka, P.G. Department of Studies in Botany, Karnatak University, Dharwad, Karnataka 580003, India. E-mail: sreenivasankud @ gmail.com © 2020 Nayaka, et al. This is an open access article distributed under the terms of the Creative Commons Attribution License -NonCommercial-ShareAlike Unported License (http://creativecommons.org/licenses/by-nc-sa/3.0/).