ABSTRACT
Efficient regulation of thermal radiation is an effective way to conserve energy consumption of buildings. Because windows are the least energy-efficient part of buildings, their thermal radiation regulation is highly demanded, especially in the changing environment, but is still a challenge. Here, by employing a kirigami structure, we design a variable-angle thermal reflector as a transparent envelope of windows for their thermal radiation modulation. The envelope can be easily switched between heating and cooling modes by loading different pre-stresses, which endow the envelope windows with the ability of temperature regulation, and the interior temperature of a building model can be reduced by ~3.3 °C under cooling mode and increased by ~3.9 °C under heating mode in the outdoor test. The improved thermal management of windows by the adaptive envelope provides an extra heating, ventilation, and air-conditioning energy savings percentage of 13% to 29% per year for buildings located in different climate zones around the world, making the kirigami envelope windows a promising way for energy-saving utilization.
ABSTRACT
Streptomyces produces many valuable and important biomolecules with clinical and pharmaceutical applications. The development of simple and highly efficient gene editing tools for genetic modification of Streptomyces is highly desirable. In this study, we developed a screening system for targeted gene knockout using a uracil auxotrophic host (ΔpyrF) resistant to the highly toxic uracil analog of 5-fluoroorotic acid (5-FOA) converted by PyrF, and a non-replicative vector pKC1132-pyrF carrying the complemented pyrF gene coding for orotidine-5'-phosphate decarboxylase. The pyrF gene acts as a positive selection and counterselection marker for recombinants during genetic modifications. Single-crossover homologous integration mutants were selected on minimal medium without uracil by reintroducing pyrF along with pKC1132-pyrF into the genome of the mutant ΔpyrF at the targeted locus. Double-crossover recombinants were generated, from which the pyrF gene, plasmid backbone, and targeted gene were excised through homologous recombination exchange. These recombinants were rapidly screened by the counterselection agent, 5-FOA. We demonstrated the feasibility and advantage of using this pyrF-based screening system through deleting the otcR gene, which encodes the cluster-situated regulator that directly activates oxytetracycline biosynthesis in Streptomyces rimosus M4018. This system provides a new genetic tool for investigating the genetic characteristics of Streptomyces species.