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.