Abstract:[Background] Secondary metabolites from mangrove actinomycetes are an important source for the discovery of small molecule drugs. [Objective] To isolate and identify the antibacterial secondary metabolites from mangrove actinomycetes. [Methods] The mangrove actinomycete strains were separated and purified using dilution plate method, and antibacterial activity of the strains were assayed by agar block and filter disk methods. The 16S rRNA gene sequence of an actinomycete strain was used for species analysis and construction of the phylogenetic tree. The fermentation broth of the actinomycete strain was analyzed by high performance liquid chromatography (HPLC), and the antibacterial compounds were purified by silica gel column chromatography and HPLC combining with activity-tracking method. The structures of the antibacterial compounds were elucidated by high resolution electrospray ionization mass spectroscopy (HR-ESI-MS) and nuclear magnetic resonance (NMR). [Results] An actinomycetes strain ZFSM1-146 with strong antibacterial activity was obtained from mangrove soil. Species and phylogenetic tree analysis showed that the strain belongs to Streptomyces antibioticus. Strain ZFSM1-146 could produce antibacterial compounds 1-3, which were identified as actinomycin XOβ, X2 and D, respectively. After preliminary medium optimization, the yield of actinomycin X2, which showed the strongest antibacterial activity among the 3 compounds, was almost twice as the original yield. [Conclusion] S. antibioticus ZFSM1-146 was obtained from mangrove soil and could produce antibacterial compound actinomycins. This study provided a valuable strain for improving the yield of actinomycins as well as producing new analogs through genetic manipulation.
