Isolation, Screening, and Identification of Novel Isolates of Actinomycetes from India for Antimicrobial Applications

Abstract

The search for novel bioactive compounds from the natural environment has rapidly been gaining momentum with the increase in multi-drug resistant (MDR) pathogens. In the present study, the antimicrobial potential of novel actinomycetes has been evaluated by initial screening of six soil samples. Primary and secondary screening was performed against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Candida albicans, Candida tropicalis, Trichophyton rubrum, and other MDR bacterial and fungal test strains, thirteen active isolates were selected for further study. Microbial strains were identified on the basis of growth conditions and other biochemical characters. Five most active microbial strains were identified using 16S rRNA sequence homology and designated as Streptomyces xanthophaeus MTCC 11938, Streptomyces variabilis MTCC 12266, Streptomyces xanthochromogenes MTCC 11937, Streptomyces levis EU 124569, and Streptomyces sp. NCIM 5500. Four antibacterial and three antifungal compounds isolated from the above five isolates were purified and partially characterized using UV absorption and IR spectra. Two antibacterial metabolites, belong to chromone and peptide antibiotic, respectively. The antifungal compounds were found to be of non-polyene nature. In conclusion, we study the isolation of novel bacterial strains of actinomycetes for producing novel compounds having antibacterial and antifungal activities from the unexplored agro-ecological niches of India. Also, this study paves the way for further characterization of these isolates of Streptomyces sp. for their optimum utilization for antimicrobial purposes.

Screening of Actinomycetes from Turmeric (Curcuma longa L.) and Ginger (Zingiber officinale) Rhizosphere for Antifungal Activity

“…1. Contrary to most studies [27][28][29] where Streptomyces were mostly reported as the dominant actinomycetes isolated, in this study the most dominant strains were non-Streptomyces (66.67%). The abundance of rare actinomycetes in this study might be attributed to the creativity of supplementing the isolation media with CaCO 3 .…”

Isolation and screening of antibiotic producing actinomycetes from rhizosphere and agricultural soils

“…The differences in the ability to produce the clear zone were presumably dependent on the secondary metabolites that were produced by test isolates. This assumption was supported by Dharmawan et al (2009) and Singh et al (2016) The resistance test isolates were S. aureus ATCC25923, E. coli ATCC25922, P. aeruginosa ATCC25853, S. pneumoniae ATCC49619, S. typhi ATCC 6539 and S. boydii (clinical isolate) that were resistant to one of the antagonistic isolates. The most sensitive one was S. aureus (clinical isolate) that was inhibited by all isolates crude extract; they vary in inhibition zone diameter.…”

“…In recent years, new resistant strains emerge more quickly while the rate of discovery of new antibiotics is slowing down (Oskay et al, 2004;Parungao et al, 2007). This necessitates the screening of microorganisms for antimicrobial activity for the production of new and novel drugs (Singh et al, 2016). Hence, intensive search for new antibiotics has become imperative worldwide especially from new actinomycetes (Oskay et al, 2004;Parungao et al, 2007).…”

Antibacterial and Antifungal Property of Actinomycetes Isolates from Soil and Water of Nepal

“…Similarly, MIC was 2.5mg/ml against VRE, Shigella dysenteriae and Klebsella pneumoniae. 17 In contrast, Satish and Kokati(2017) reported low MIC value of 1mg/ml for MDRSA. 18 MIC value is affected by many parameters including susceptibility of organisms, type of microorganism, concentration and type of bioactive metabolites, composition of cultural medium, incubation temperature and time.…”