Screening of Thiopeptide-Producing Streptomycetes Isolated From the Rhizosphere Soil of Juniperus excelsa

Abstract

The identifcation of an increasing number of drug-resistant pathogens has stimulated the development of new therapeutic agents to combat them. Microbial natural products are among the most important elements when it comes to drug discovery. Today, thiopeptide antibiotics are receiving increasing research attention due to their potent activity against Gram-positive bacteria. In this study, we demonstrated the successful use of a whole-cell microbial biosensor (Streptomyces lividans TK24 pMO16) for the specifc detection of thiopeptide antibiotics among the native actinomycete strains isolated from the rhizosphere soil of Juniperus excelsa (Bieb.). Among the native strains, two strains of Streptomyces, namely sp. Je 1–79 and Je 1–613, were identifed that were capable of producing thiopeptide antibiotics. A multilocus sequence analysis of fve housekeeping genes (gyrB, atpD, recA, rpoB, and trpB) classifed them as representatives of two diferent species of the genus Streptomyces. The thiopeptide antibiotics berninamycin A and B were identifed in the extracts of the two strains by means of a dereplication analysis. The berninamycin biosynthetic gene cluster was also detected in the genome of the Streptomyces sp. Je 1–79 strain and showed a high level of similarity (93%) with the ber cluster from S. bernensis. Thus, the use of this whole-cell biosensor during the frst stage of the screening process could serve to accelerate the specifc detection of thiopeptide antibiotics.