Screening, identification and characterization of marine antimicrobial actinomycetes Y15

Abstract:

[Objective] This paper aims at screening marine actinomycetes with broad-spectrum and producing efficient antimicrobial active substance, to lay the foundation for the development of new antibiotics. [Methods] Using Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Listeria monocytogenes as indicator bacteria, target bacteria from sea mud samples was primarily screened with agar block method, and further screened with punching diffusion method; twenty indicator bacteria were used to examine the antimicrobial spectrum of the new isolates Y10, Y11, Y15, Y16 and Y21; taxonomic status of the strain Y15 was determined by morphologic observation and 16S rRNA gene sequence analysis; mode of action of antimicrobial active substance to Listeria monocytogenes was studied according to indicator bacteria OD600 value; the antimicrobial activity was used as an index to study the physical and chemical properties of antimicrobial active substances produced by Y15. [Results] A total of 12 strains showing antimicrobial activities to antagonistic strains were isolated; wherein Y15 had the widest spectrum, and could be against 18 of the 20 kinds of indicator strains, and on four media it could produce antimicrobial active substances. The 16S rRNA gene sequence analysis showed that Y15 had closest relationship with Micromonospora endolithica. Activity of Y15 antimicrobial metabolites reached a maximum of 480 AU/mL in 144 h, maintained 320 AU/mL from 168 h to 216 h. The action mode of Y15 antimicrobial active substance to Listeria monocytogenes was sterilization. Antimicrobial activity of Y15 antimicrobial active substances remained stable from ?20 °C to 60 °C, and gradually declined from 80 °C to 120 °C, but still retained 37.5% at 120 °C for 30 min; antimicrobial activity remained stable from pH 7.0 to 10.0, and from pH 2.0 to 6.0 and pH 11.0 to 12.0 antimicrobial activity declined; Y15 antimicrobial substances processed in the UV and four kinds of enzymes (Proteinase K, Trypsin, Papain and α-Amylase) were stable, there were non-protein and non-peptide antimicrobial substances. [Conclusion] The active substances produced by Y15 showed good antimicrobial spectrum and activity, and were relatively stable, indicating a high application value in the future.

Key words:Marine antimicrobial actinomycetes, Metabolites, Physicochemical properties, Antimicrobial spectrum, Micromonospora