Genome Mining Of Ribosomal Peptides In The Salt-tolerant Strain Streptomyces Thermolilacinus SPC6

Today,the bacterial drug resistance is more and heavier.Novel drugs needed to be developed to defeat this condition.Microbial natural products are the source of drug development,although it is more and more difficult to find new natural products with good activity from the microorganism of the traditional environment.The scientist tries to discover new natural products from microorganism of the extreme environment,besides this new technology also be exploited for natural products discovery.Streptomyces thermolilacinus SPC6(hereinafter referred to as SPC6)is a strain of Streptomyces isolated from the Badain Jaran Desert.It can grow rapidly in a medium with 1M NaCl that exhibits salt tolerance.Because of its special ecological adaptability,it is speculated that this strain has unique metabolic pathways to biosynthesize special small molecular compounds even macromolecules.We performed genomic sequencing of SPC6 and analyze of its secondary metabolism-related genes and gene clusters,about 19 typical natural product biosynthetic gene clusters were discovered,indicating that SPC6 has a strong biosynthetic ability of natural products.To date,there have been few reports on natural products produced by this strain,with the main reason that most of its biosynthetic gene clusters are silent or their production is trace.It is difficult to find and identify these natural products by traditional chemical separation strategy.To overcome this bottleneck,we exploited a creative approach using the combination of genome mining and metabolic engineering to unveil these natural products in SPC6.The S2C8 gene cluster as the specific research object in study,and S2C8 is a typical ribosomal biosynthetic gene cluster.Ribosomal peptides are a class of compounds which are ribosomally synthesized and posttranslationally modified peptides.Many of them have definite biological activities,especially the lanthipeptides have good antimicrobial activity.We found the gene cluster named S2C8 in the SPC6 genome encoding a novel ribosomal peptide synthetase next to upstream polyketide synthase and downstream non-ribosomal peptide synthetase.This unique genetic logic indicated that S2C8 likely biosynthesize a novel polypeptide compound.We disrupted the gene cluster S2C8 by the in-frame knockout approach and performed fermentation of mutant strain with the wild-type strain as a control.Compared to the extract of fermentation of wildtype strain,the extract of fermentation of the mutant showed a significant activity disappeared,indicating that the S2C8 gene cluster is responsible for biosynthesis of some putative natural products with good activity.These putative compounds will be identified by large-scale fermentation,separation and structure elucidation and they will be provided as candidates for drug screening.