Isolation and Characterization of Marine and Terrestrial Actinomycetes Using a Medium Supplemented with NaCl

Abstract

Actinomycetes isolated from marine sediments in neritic zone in the sea around Japan were compared with terrestrial isolates. Among actinomycetes that are macroscopically Streptomyces and Micromonospora, marine isolates of both genera were found to have higher NaCl tolerance than terrestrial ones. Around 37% of Streptomyces and 26% of Micromonospora that were isolated from the marine environment could tolerate up to 12% and 5% NaCl, respectively. However, no terrestrial isolates could tolerate NaCl at these concentrations. The results of the 16S rRNA gene sequence analysis of 10 strains with high NaCl tolerance among these marine isolates showed that they had a close phylogenetic relationship with terrestrial strains isolated previously. The isolation of actinomycetes from marine sediments and terrestrial soils in the presence or absence of 6% NaCl in media revealed that the selective pressure of NaCl demonstrated no clear difference between both isolates. Terrestrial strains isolated by using a medium supplemented with 6% NaCl exhibited a high frequency (95%) of NaCl tolerance up to 9%. The highly NaCl tolerant strains isolated from terrestrial soils were frequently found to produce antimicrobial substances in the presence of seawater. Almost 75% of strains tested showed antimicrobial activities against Bacillus subtilis PCI 219 and 40% against Candida albicans 3147. It was suggested that the frequency of microorganisms with antimicrobial properties was increased in the medium supplemented with seawater.