Screening of novel glycopeptide compounds in actinomycetes genomes by using genetic tools

Microbial natural products, from actinomycetes in particular, have been the sources of the most important antimicrobial drug classes, including the β-lactams, tetracyclines, macrolides, aminoglycosides, rifamycins and glycopeptides. The discovery of new antibiotics has been accomplished by chemically or genetically screening methods from organisms that have potential for production. One of the most current methods used in novel antibiotic screening studies is to search the conserved biosynthetic genes in the antibiotic biosynthetic gene clusters of microorganisms. Glycopeptide antibiotics (GPA) are natural products from the actinomycetes have long served as drugs of last resort for the treatment of antibiotic-resistant Gram-positive bacterial infections. The chemical diversity of the GPA class is achieved through glycosylation, halogenation, methylation, and acylation of the core. These modifications are improved the solubility, stability and activity of the molecule. Cross-linking of aromatic side chains by monooxygenases is another necessary modification in GPA biosynthesis. In order to assess the presence of the GPA biosynthetic systems in 8 local Streptomyces strains, it was used the degenerate primers for amplification of a monooxygenase gene, oxyC. PCR products were cloned and sequenced. Translated protein sequences were compared with those in databases through the NCBI (National Center for Biotechnology Information, US) using BLASTx program. Sequences were aligned using multiple sequence alignment tools from Clustal W in MEGA 6.0 package. According to the bioinformatic analysis, different monooxygenase genes belong to both glycopeptide or other antibiotics were determined. The phylogenetic analysis showed that the genes obtained in this study were most closely related to oxyA (CA19, CA17, AS36 and CA18) and oxyB (CS38) genes of the GPA complestatin from Streptomyces lavendulae. The Streptomyces isolates used in this study are promising candidates to look for novel GPA and other natural products.