Spatiotemporal characteristics of ozone and the formation sensitivity over the Fenwei Plain.

High surface ozone (O3) levels affect human and environmental health. The Fenwei Plain (FWP), one of the critical regions for China's "Blue Sky Protection Campaign", has reported severe O3 pollution. This study investigates the spatiotemporal properties and the causes of O3 pollution over the FWP using high-resolution data from the TROPOspheric Monitoring Instrument (TROPOMI) from 2019 to 2021. This study characterizes spatial and temporal variations in O3 concentration by linking O3 columns and surface monitoring using a trained deep forest machine learning model. O3 concentrations in summer were 2-3 times higher than those found in winter due to higher temperatures and greater solar irradiation. The spatial distributions of O3 correlate with the solar radiation showing decreased trends from the northeastern to the southwestern FWP, with the highest O3 values in Shanxi Province and the lowest in Shaanxi Province. For urban areas, croplands and grasslands, the O3 photochemistry in summer is NOx-limited or in the transitional regime, while it is VOC-limited in winter and other seasons. Reducing NOx emissions would be effective for decreasing O3 levels in summer, while VOC reductions are necessary for winter. The annual cycle in vegetated areas included both NOx-limited and transitional regimes, indicating the importance of NOx controls to protect ecosystems. The O3 response to limiting precursors shown here is of importance for optimizing control strategies and is illustrated by emission changes during the 2020 COVID-19 outbreak.

[Cloning and expression of Streptomyces lividans promoters].

BamHI restriction fragments from Streptomyces lividans TK24 chromosome DNA have been cloned into BamHI site of promoter probe plasmid pIJ486. Transformants were selected on the medium containing 5 micrograms/ml of neomycin. Four recombinant plasmids pMG1(10.6 kb), pMG40(7.6 kb), pMG50(10.8 kb) and pMG88(7.92 kb), were found and designated respectively. The inserted fragments in pMG40 and pMG50 were reduced to 0.78kb and 2.2 kb by BglII digestion and rejoining. The different levels of neomycin and kanamycin resistance of these recombinant plasmids were determined. The results revealed that pMG50-25 showed a high level of neomycin resistance (90 micrograms/ml) and kanamycin resistance (500 micrograms/ml).

[Subcloning and sequencing of the Streptomyces griseus DNA fragment with promoter activity in E. coli].

A 410-bp DNA fragment of Streptomyces griseus No.45 with in vivo promoter activity in E. coli has been isolated by subcloning the cloning strain E. coli No.8-1. The result of sequencing shows that the promoter fragment contains 50.5% G + C bases. It has some repeat sequences. It shows good homology to the E. coli promoter consensus sequences in -10 and -35 regions. There are 18 bp between the two regions. It has two regions that are similar to SD sequence in E. coli and consensus sequence in SEP (Streptomyces-E.coli-type promoter) of Streptomyces lividans respectively. There is 1 Alu I site, 1 Cla I site, 2 Mbo I sites, 3 NlaIII sites and 1 PvuII site in the promoter fragment.

[Cloning and expression of E. coli glucose isomerase gene in Streptomyces lividans].

E. coli glucose isomerase gene was cloned into Streptomyces lividans using shuttle plasmid vector pSE-3. First plasmid pXI203 was constructed in E. coli using plasmids pXI200 (containing 1.6 kb glucose isomerase gene) and pGEM-3 digested with EcoR1. Then, recombinant plasmid pSEX100 was also constructed in E. coli using plasmids pXI203 and pSE-3 digested with HindIII. When the pSEX100 was transformed into Streptomyces lividans protoplasts, recombinants were obtained on R5YE medium containing 50 micrograms/ml neomycin and 50 micrograms/ml thiostrepton. The results showed that the E. coli glucose isomerase gene cloned and expressed in Streptomyces lividans via the analysis of restriction enzyme digestion as well as the detection of the glucose isomerase activity.