Project description:The gram-positive bacterium, Streptomyces avermitilis holds industrial importance, which produces widely used anthelmintic agent, avermectin. Furthermore, S. avermitilis is generally considered as a prominent heterologous gene expression host for diverse secondary metabolites biosynthesis. However, despite of its industrial importance, it largely remains unknown how its genome is organized and regulated for timely gene expression. Here, we determined 1,601 transcription units (TU) encoded in its genome using the integrated analysis of high-throughput sequencing data including dRNA-Seq, Term-Seq, RNA-Seq, and Ribo-Seq. In addition to TU cataloguing, these information-rich results also revealed the presence of diverse regulatory elements for the transcriptional and translational control of individual TU, such as promoters, 5¢-UTRs, terminators, 3¢-UTRs, and riboswitches. The conserved promoter sequences for transcription initiation were identified from 2,361 transcription start sites as 5¢-TANNNT and 5¢-TGAC for -10 and -35 elements, respectively. Interestingly, the -35 element and spacer length between them were critical for transcriptional regulation of functionally distinct genes. Total 2,017 transcription termination sites were detected from Term-Seq analysis, revealing that stem structure formation is a prerequisite for transcription termination and that Rho-independent termination prevails in S. avermitilis. Lastly, the TU architecture suggests the presence of novel small RNAs and cis-regulatory elements in the genome. Our findings will serve as invaluable resources for comprehensive understanding on regulatory features of S. avermitilis. Moreover, it is anticipated the elevation of its potential as the heterologous expression host for diverse secondary metabolite biosynthesis.
Project description:Background: During the lifetime of a fermenter culture, the soil bacterium S. coelicolor undergoes a major metabolic switch from exponential growth to antibiotic production. We have studied gene expression patterns during this switch, using a specifically designed Affymetrix genechip and a high-resolution time-series of fermenter-grown samples. Results: Surprisingly, we find that the metabolic switch actually consists of multiple finely orchestrated switching events. Strongly coherent clusters of genes show drastic changes in gene expression already many hours before the classically defined transition phase where the switch from primary to secondary metabolism was expected. The main switch in gene expression takes only 2 hours, and changes in antibiotic biosynthesis genes are delayed relative to the metabolic rearrangements. Furthermore, global variation in morphogenesis genes indicates an involvement of cell differentiation pathways in the decision phase leading up to the commitment to antibiotic biosynthesis. Conclusions: Our study provides the first detailed insights into the complex sequence of early regulatory events during and preceding the major metabolic switch in S. coelicolor, which will form the starting point for future attempts at engineering antibiotic production in a biotechnological setting. Keywords: time course
Project description:Here, we address the transcriptional response to both novobiocin-induced rapid chromosome relaxation or long-term topological imbalance, both increased and decreased supercoiling, in environmental antibiotic-producing bacteria belonging to the Streptomyces genus.