Antibacterial Compounds and Draft Genome Sequence of Streptomyces sp. PA5.6 Isolated from Deciduous Dipterocarp Forest Soils, University of Phayao, Thailand

Abstract

Antibiotic resistance is a major problem in the control of infectious diseases. To overcome this obstacle, a common approach is to search for novel antimicrobial drugs from natural sources, especially microorganisms such as Streptomyces. Streptomyces has long been demonstrated to produce bioactive secondary metabolites with antimicrobial activities. The objectives of this research were to isolate and characterize Streptomyces strains from the deciduous dipterocarp forest soils in the University of Phayao, and to evaluate their metabolites for antibacterial activities. The results show that the morphological and physiological characteristics of PA5.6 are consistent with those of the genus Streptomyces. Furthermore, a comparative analysis of the whole genome sequence verified that PA5.6 represents a novel species within the genus Streptomyces. The genome sequence analysis of Streptomyces sp. PA5.6 revealed a total length of 9,146,340 bp, a G + C content of 71.1 %, and an N50 scaffold of 320,345 bp. The antiSMASH analysis revealed putative secondary metabolite Biosynthetic Gene Clusters (BGCs) involved in the biosynthesis of antimicrobial metabolites, including terpene, Type I PKS, NRPS and lassopeptide gene clusters. Functional prediction of these gene clusters indicates that they are involved in the biosynthesis of several antimicrobial-associated metabolites, such as albaflavenone, monensin and citrulassin D. Streptomyces sp. PA5.6 culture supernatant and its crude ethyl acetate extract exhibited antibacterial activity against several drug-resistant, bacterial pathogens, including S. aureus, E. faecalis, E. coli, P. aeruginosa, A. baumannii, MRSA, VREF, ESBL-E. coli and CRPA. The GC-MS analysis of the crude ethyl acetate extracts revealed benzeneacetic acid, benzeneacetic acid, 4-hydroxy and benzeneacetamide as major active compounds metabolites. In conclusion, Streptomyces sp. PA5.6 exhibited promising potential for producing bioactive compounds against bacterial pathogens. HIGHLIGHTSThe Streptomyces sp. PA5.6 isolated from the soil in the deciduous dipterocarp forest and was identified as a new species within the genus Streptomyces by comparative analysis of the whole genome sequence. The crude ethyl acetate extract of Streptomyces sp. PA5.6 exhibited antibacterial activity against bacterial pathogens. GC-MS analysis of crude ethyl acetate extract showed major and minor compounds that exhibit antimicrobial activity. GRAPHICAL ABSTRACT