Streptomycetes are Gram-positive bacteria of Actinomycetales. These organisms can produce many economically important secondary metabolites. With the development of molecular biology, gene sequencing technology and synthetic biology, people gained a better understanding of the Streptomyces family. The means to transform genome on the molecular level is also increasing. By simplifying the Streptomyces genome rationally and efficiently, it will improve the yield and quality of the metabolites as well as reduce the consumption of the substrates. Markerless knockout is an important way to carry out genetic modification. Here we describe novel genome modification techniques developed for Streptomyces in recent years with focus on the markerless knockout technologies.
Chromosomes, Bacterial ; genetics ; Gene Knockout Techniques ; methods ; Genes, Bacterial ; genetics ; Streptomyces ; genetics

In this study, we found that when Pseudomonas mendocina NK-01 accumulated intracellular carbon reserve, medium chain length poly (3-hydroxyalkanoates), it also synthesized extracellular saccharides, alginate oligosaccharides. The high carbon nitrogen ratio of culture medium facilitated alginate oligosaccharides production. We analyzed the structure of alginate oligosaccharide by Ultraviolet-Visible Spectrophotometry, Fourier Transform Infrared Spectroscopy, 1H and 13C of Nuclear Magnetic Resonance, and found that it was compounded in line from beta-D-mannuronic acids and alpha-L-gluronic acids via beta-(1-->4)/ alpha-(1-->4) bonds, which acetylated partly on the 2- and/or 3-hydroxy. In addition, we determined the weight-average molecular weight of alginate oligosaccharides by gel permeation chromatography to be 2054.
Alginates ; chemistry ; Glucuronic Acid ; biosynthesis ; chemistry ; genetics ; Hexuronic Acids ; chemistry ; Molecular Weight ; Oligosaccharides ; biosynthesis ; chemistry ; genetics ; Pseudomonas mendocina ; metabolism

Objective To investigate the characteristics of knee kinematics and ground reaction force (GRF), as well as the stress state of cartilage and meniscus in the process of lateral incisions at different cutting angles under expected conditions. Methods Kinematics and GRF data of 14 subjects at 45°, 90° and 135° cutting angle respectively under expected conditions were collected. The knee joint reaction force was obtained through the inverse dynamics calculation of Visual 3D. Based on three-dimensional (3D) finite element model of the knee joint, the contact process at 3 lateral cutting angles was simulated. ResultsUnder expected conditions, there were significant differences in knee joint kinematics characteristics at 3 cutting angles during contact process(P＜0.001), and the knee flexion increased with the cutting angle increasing; the vertical GRF decreased significantly with the cutting angle increasing (P＜0.001), while the horizontal GRF showed the opposite trend; for 3 cutting angles, the peak contact stress of patellar cartilage and femoral cartilage was larger at 90° cutting angle, the peak principal stress at anterior cruciate ligament (ACL) contact point was also larger at 90° cutting angle, and the following was at 135° and 45° cutting angle, respectively; the peak contact stress of lateral femoral cartilage was larger than that of medial femoral cartilage at 3 cutting angles. Conclusions The risk of knee joint injury is higher at 90° cutting angle, and the stress state of knee joint at 135° cutting angles is better than that at 90° cutting angle, and the risk of knee joint injury does not increase with the increase of cutting angle under expected conditions.