Development of a synthetic oxytetracycline-inducible expression system for streptomycetes using de novo characterized genetic parts

Precise control of gene expression using exogenous factors is of great significance. To develop ideal inducible expression systems for streptomycetes, new genetic parts, oxytetracycline responsive repressor OtrR, operator otrO, and promoter otrBp from Streptomyces rimosus, were selected de novo and characterized in vivo and in vitro. OtrR showed strong affinity to otrO (KD = 1.7 × 10–10 M) and oxytetracycline induced dissociation of the OtrR/DNA complex in a concentration-dependent manner. On the basis of these genetic parts, a synthetic inducible expression system Potr* was optimized. Induction of Potr* with 0.01–4 μM of oxytetracycline triggered a wide-range expression level of gfp reporter gene in different Streptomyces species. Benchmarking Potr* against the widely used constitutive promoters ermE* and kasOp* revealed greatly enhanced levels of expression when Potr* was fully induced. Finally, Potr* was used as a tool to activate and optimize the expression of the silent jadomycin biosynthetic gene cluster in Streptomyces venezuelae. Altogether, the synthetic Potr* presents a new versatile tool for fine-tuning gene expression in streptomycetes

A Novel Delay Linear Coupling Logistics Map Model for Color Image Encryption

With the popularity of the Internet, the transmission of images has become more frequent. It is of great significance to study efficient and secure image encryption algorithms. Based on traditional Logistic maps and consideration of delay, we propose a new one-dimensional (1D) delay and linearly coupled Logistic chaotic map (DLCL) in this paper. Time delay is a common phenomenon in various complex systems in nature, and it will greatly change the dynamic characteristics of the system. The map is analyzed in terms of trajectory, Lyapunov exponent (LE) and Permutation entropy (PE). The results show that this map has wide chaotic range, better ergodicity and larger maximum LE in comparison with some existing chaotic maps. A new method of color image encryption is put forward based on DLCL. In proposed encryption algorithm, after various analysis, it has good encryption performance, and the key used for scrambling is related to the original image. It is illustrated by simulation results that the ciphered images have good pseudo randomness through our method. The proposed encryption algorithm has large key space and can effectively resist differential attack and chosen plaintext attack

A Nonlinearly Modulated Logistic Map with Delay for Image Encryption

Considering that a majority of the traditional one-dimensional discrete chaotic maps have disadvantages including a relatively narrow chaotic range, smaller Lyapunov exponents, and excessive periodic windows, a new nonlinearly modulated Logistic map with delay model (NMLD) is proposed. Accordingly, a chaotic map called a first-order Feigenbaum-Logistic NMLD (FL-NMLD) is proposed. Simulation results demonstrate that FL-NMLD has a considerably wider chaotic range, larger Lyapunov exponents, and superior ergodicity compared with existing chaotic maps. Based on FL-NMLD, we propose a new image encryption algorithm that joins the pixel plane and bit-plane shuffle (JPB). The simulation and test results confirm that JPB has higher security than simple pixel-plane encryption and is faster than simple bit-plane encryption. Moreover, it can resist the majority of attacks including statistical and differential attacks

MOESM5 of Genome-wide identification and evaluation of constitutive promoters in streptomycetes

Additional file 5: Table S2. The 500-bp regions upstream of the 166 genes with constant expression profiles

MOESM3 of Genome-wide identification and evaluation of constitutive promoters in streptomycetes

Additional file 3: Dataset S2. Genes eliminated in each rational selection step