Isolation, classification, phylogenetic analysis and scanning electron microscopy of halophilic, halotolerant and alkaliphilic actinomycetes isolated from hypersaline soil

Abstract

Actinomycetes were isolated by plating of serially diluted samples onto humic acid-vitamin agar prepared with or without NaCl and characterized by physiological and phylogenetical studies. A total of 16 strains were isolated from hypersaline soil in Mongolia. All strains showed alkaliphilic characteristics and were able to abundantly grow in media with pH 9.0. Six strains were halotolerant actinomycetes (0 to 12.0% NaCl) and 10 strains were moderately halophiles (3.0 to 12.0% NaCl). Most strains required moderately high salt (5.0 to 10.0%) for optimal growth but were able to grow at lower NaCl concentrations. Among the 16 strains, 5 were able to grow at 45°C. Among the group of moderate halophilic actinomycetes, 9 strains were phylogenetically detected under the genus Nocardiopsis in the family Nocardiopsaceae. Results of scanning electron microscopic study demonstrated that most of the moderately halophilic strains under the genus Nocardiopsis, produce synnemata structure. Overall phylogenetic analysis based on 16S rRNA gene sequences analysis revealed that all the 16 strains fell into 4 different genera: Nocardiopsis (9 strains), Isoptericola, (2 strains), Nesterenkonia (2 strains), Streptomyces (3 strains). This preliminary study demonstrated that the genus Nocardiopsis is abundant and a recoverable actinomycetes group in Mongolian saline soil. Based on the position in phylogenetic tree of 16 isolates, there were new clusters which supposed to be novel species under the genera Nocardiopsis (possible new species 1) and Isoptericola (possible new species 1) in the family Nocardiopsaceae and Promicromonosporaceae, respectively.

Screening of Antibiotic producing Actinomycetes for Antibiosis from soil of Sunsari, Nepal

“…multi-drug resistant pathogens (Isoken et al, 2010) like Shigella dysenteriae, Methicillin-Resistant Staphylococcus aureus (MRSA), Vancomycin-Resistant Enterococci, Klebsiella spp., and Pseudomonas aeruginosa, among others (Bhatnagar & Kim, 2010;Saadoun et al, 1999;Selvameenal et al, 2009;Servin et al, 2008).…”

“…Though not entirely, bacteria are the main source of the majority of antibiotics used today in clinical treatment (Russell, 2004). Actinomycetes are gram positive, rod shaped slow growing bacteria (Holt et al, 1994;Isoken et al, 2010;Oskay et al, 2004a). They have high G+C content (>55%) in their DNA and are the best common sources of antibiotics (Roitch et al, 2017).…”

“…They have high G+C content (>55%) in their DNA and are the best common sources of antibiotics (Roitch et al, 2017). They are widely distributed in both natural and man-made settings, including soil, freshwater, lakes, compost dust, plant wastes, and food products (Isoken et al, 2010). For many years, researchers have been experimenting with various microbes to develop novel antibiotics (Oskay et al, 2004b).…”