Identification and antimicrobial activities of Streptomyces, Micromonospora, and Kitasatospora strains from rhizosphere soils

Rhizosphere soils are the major habitat of various bacteria, especially the actinobacteria. In this study, 17 actinomyceteswere isolated from rhizosphere soil samples collected from the plants, including Barringtonia racemosa, Albizziaodoratissima, Spondia spinnata, and Azadirachta indica. On the basis of 16S rRNA gene analysis (99.0%–100%similarity), the isolates were belonged to genera Streptomyces (10 isolates), Micromonospora (5 isolates), andKitasatospora (2 isolates). They were identified as Streptomyces sioyaensis (2 isolates), Streptomyces vietnamensis(2 isolates), Streptomyces bungoensis (2 isolates), each of Streptomyces psammoticus, Streptomyces purpurascens,Streptomyces hydrogenans, Streptomyces lucensis; Micromonospora schwarzwaldensis, Micromonospora chersina,Micromonospora terminalae, Micromonospora chaiyaphumensis, Micromonospora rhizosphaerae and two isolatesas Kitasatospora putterlickiae. On the results of antimicrobial activities, three isolates presented the good activitiesagainst Candida albicans ATCC 10231, and Escherichia coli ATCC 25922, while 10 isolates exhibited the goodactivities against Staphylococcus aureus ATCC 25923 and 11 isolates exhibited activities against Bacillus subtilisATCC 6633. Among them, JA03 showed 98.95% similarity of 16S rRNA gene sequence to S. psammoticus NBRC13971T, this isolate might be the novel species of actinomycetes

Distribution and antimicrobial activity of Thai marine actinomycetes

A total of 41 actinomycetes were isolated from marine samples collected in Thailand. On the basis of morphology,chemotaxonomy, and 16S rRNA gene sequence analysis, they were identified as Salinispora (13 isolates),Micromonospora (11 isolates), Nocardia (1 isolate), Verrucosispora (2 isolates), and Streptomyces (14 isolates).The antimicrobial activity screening revealed that two Micromonospora isolates, 12 Salinispora isolates and 10Streptomyces isolates showed activity against Staphylococcus aureus ATCC 25923, Kocuria rhizophila ATCC 9341,Bacillus subtilis ATCC 6633, Escherichia coli NIHJ KC213, Candida albicans KF1, and Mucor racemosus IFO 4581.Based on this study, the production media and strains were the main factors that influenced the antimicrobial activity