Microbial transformation of neomycin by a mutant of neomycin-producing Streptomyces fradiae

Utilizing a mutant of neomycin-producing Streptomyces fradiae mutagenized with neutron radiation, biotransformation of neomycin into modified compounds was studied. The biotransformation products were isolated by ion exchange chromatography and monitored by thin layer chromatography bioautography (TLCB). Antibacterial activity of biotransformation products against ten species of bacteria including four plant pathogens was tested qualitatively by TLCB and detected quantitatively by Oxford cup method. The minimal inhibitory concentration (MIC) of biotransformation products was tested by agar diffusion method. Three isolated transformation products had obvious antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Proteus vulgaris and Pseudomonas solanacarum. At the concentration of 50 μg/ml, the transformation product X had a similar antibacterial effect with neomycin but the transformation product Y and Z showed a decreased effect compared to neomycin except for P. vulgaris and P. solanacarum. However, the results from MIC analysis demonstrated that only the transformation product X maintained the same inhibitory effect with neomycin.Key words: Neomycin, biotransformation, Streptomyces fradiae, mutant, neutron radiation

Exogenous trehalose improves growth under limiting nitrogen through upregulation of nitrogen metabolism

The trehalose (Tre) pathway has strong effects on growth and development in plants through regulation of carbon metabolism. Altering either Tre or trehalose 6-phosphate (T6P) can improve growth and productivity of plants as observed under different water availability. As yet, there are no reports of the effects of modification of Tre orT6P on plant performance under limiting nutrition. Here we report that nitrogen (N) metabolism is positively affected by exogenous application of Tre in nitrogen-deficient growing conditions. Spraying foliage of tobacco (Nicotiana tabacum) with trehalose partially alleviated symptoms of nitrogen deficiency through upregulation of nitrate and ammonia assimilation and increasing activities of nitrate reductase (NR), glycolate oxidase (GO), glutamine synthetase (GS) and glutamine oxoglutarate aminotransferase (GOGAT) with concomitant changes in ammonium (NH4 +) and nitrate (NO3 −) concentrations, glutamine and amino acids. Chlorophyll and total nitrogen content of leaves and rates of photosynthesis were increased compared to nitrogen-deficient plants without applied Tre. Total plant biomass accumulation was also higher in Tre -fed nitrogen-deficient plants, with a smaller proportion of dry weight partitioned to roots, compared to nitrogen-deficient plants without applied Tre. Consistent with higher nitrogen assimilation and growth, Tre application reduced foliar starch. Minimal effects of Tre feeding were observed on nitrogen-sufficient plants. The data show, for the first time, significant stimulatory effects of exogenous Tre on nitrogen metabolism and growth in plants growing under deficient nitrogen. Under such adverse conditions metabolism is regulated for survival rather than productivity. Application of Tre can alter this regulation towards maintenance of productive functions under low nitrogen. This has implications for considering approaches to modifying the Tre pathway for to improve crop nitrogen-use efficiency and production

A specific mapping between topological superconductors and topological insulators

An interesting mapping between topological insulators (TI) and topological superconductors (TS) is presented. We show that if a Hamiltonian of a TI is purely imaginary, there is a corresponding TS with the Hamiltonian in the same form, but under a Majorana basis. Starting from the well-known TI in different dimensions, we perform the mapping explicitly. New TS systems and new understanding of the known TS are obtained. The result provides a natural way to construct topological nontrivial gapped Majorana systems, which may be engineered in the experimental setups with Majorana quasiparticles as the low-energy excitations

Is proximal tibial tubercle osteotomy superior to distal tibial tubercle osteotomy for medial compartmental osteoarthritis? A meta-analysis

Abstract Background Open-wedge high tibial osteotomy (OWHTO) is commonly performed for the treatment of medial compartment knee osteoarthritis (KOA), and is classified into proximal tibial tubercle osteotomy (PTO) and distal tibial tubercle osteotomy (DTO). The PTO osteotomy point is generally located about 3–4 cm below the joint of the proximal tibia, and the osteotomy line points to the upper part of the proximal tibiofibular joint. The DTO osteotomy point is generally located about 0.5–1.0 cm below the tibial tubercle, and the osteotomy line points to the contralateral cortex. However, there is currently no consensus on which surgical technique is superior. The purpose of our study was to investigate which among the two is superior for medial KOA, with respect to knee joint parameters, clinical function, and complications. Methods This study was conducted as per the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The Cochrane Central Library, MEDLINE, Embase, PubMed, CNKI, and WanFang databases were systematically searched for trials comparing PTO and DTO in patients with medial compartment KOA, from inception until March 2022. The meta-analysis was conducted using RevMan 5.2 software. The Cochrane risk-of-bias tool was used to assess methodological quality. Statistical analysis was performed with Stata 12.0. Outcomes of interest included the Insall-Salvati index (ISI), Caton-Deschamps index (CDI), Blackburne-Peel index (BPI), posterior tibial slope (PTS), and the Hospital for Special Surgery (HSS) knee-rating scale. Results A total of 15 retrospective studies (910 knees) were included. There were no significant differences in the age or sex of included patients. There was a significant difference in the ISI, CDI, BPI, and PTS between the two groups (all p ≤ 0.05). Further, DTO was associated with a significantly greater number of postoperative complications (p  0.05). Conclusions Compared with DTO, PTO is associated with a greater incidence of postoperative patella baja and increased PTS, whereas DTO is associated with more postoperative complications. Nevertheless, both can significantly correct knee varus deformity and improve knee function; their early knee function scores are also similar. Trial Registration. Prospective Register of Systematic Reviews (PROSPERO) registration number CRD42021284443

Effect of PBAT Biodegradable Mulch Film Extract on Seed Germination and Seedlings Metabolism of Tobacco

Poly(butylene adipate-co-terephthalate) biodegradable mulch film (PBAT-BMF) is gradually applied in agricultural production, but its potential ecological risks have not been studied so far. In this paper, methyl tert-butyl ether (MTBE) was used to extract organic compounds from PBAT-BMF to evaluate its effects on tobacco seed germination and seedling metabolism. The results showed that six organic compounds were found in the extract of PBAT-BMF, among which the content of diisopropylphenyl isocyanate was the highest at 557.27 μg g−1. A germination test showed that the extract scan inhibited the germination of tobacco seeds. The germination time was 1 d later than the control(CK), and the germination percentage and germination energy were non-significantly decreased by 2.50% and 1.00%. In contrast, the extracts significantly affected the root length, and seedlings height (p < 0.01), decreased by 0.24 cm and 0.28 cm, respectively. A metabolic analysis revealed that the extracts have a certain stress effect on tobacco seedlings and showed an up-regulating effect on soluble sugar, critical organic acid, biogenic amine, and down-regulating alkaloid, which indicated that the carbon and nitrogen metabolism pathway of the tricarboxylic acid cycle and alkaloid synthesis were disturbed. These results indicated that organic compounds extracted from PBAT-BMF had stress effects on germination and the growth of tobacco seeds, which significantly changed the metabolism pathway. This study can provide a theoretical basis for the development and application of PBAT-BMF

Effect of PBAT Biodegradable Mulch Film Extract on Seed Germination and Seedlings Metabolism of Tobacco

Poly(butylene adipate-co-terephthalate) biodegradable mulch film (PBAT-BMF) is gradually applied in agricultural production, but its potential ecological risks have not been studied so far. In this paper, methyl tert-butyl ether (MTBE) was used to extract organic compounds from PBAT-BMF to evaluate its effects on tobacco seed germination and seedling metabolism. The results showed that six organic compounds were found in the extract of PBAT-BMF, among which the content of diisopropylphenyl isocyanate was the highest at 557.27 μg g−1. A germination test showed that the extract scan inhibited the germination of tobacco seeds. The germination time was 1 d later than the control(CK), and the germination percentage and germination energy were non-significantly decreased by 2.50% and 1.00%. In contrast, the extracts significantly affected the root length, and seedlings height (p < 0.01), decreased by 0.24 cm and 0.28 cm, respectively. A metabolic analysis revealed that the extracts have a certain stress effect on tobacco seedlings and showed an up-regulating effect on soluble sugar, critical organic acid, biogenic amine, and down-regulating alkaloid, which indicated that the carbon and nitrogen metabolism pathway of the tricarboxylic acid cycle and alkaloid synthesis were disturbed. These results indicated that organic compounds extracted from PBAT-BMF had stress effects on germination and the growth of tobacco seeds, which significantly changed the metabolism pathway. This study can provide a theoretical basis for the development and application of PBAT-BMF

Determination of Residual Diisocyanates and Related Diamines in Biodegradable Mulch Films Using N-Ethoxycarbonylation Derivatization and GC-MS

Diisocyanates are highly reactive compounds with two functional isocyanate groups. The exposure of diisocyanates is associated with severely adverse health effects, such as asthma, inflammation in the respiratory tract, and cancer. The hydrolysis product from diisocyanates to related diamines is also a potential carcinogen. Here, we developed an effective, accurate, and precise method for simultaneous determination of residual diisocyanates and related diamines in biodegradable mulch films, based on N-ethoxycarbonylation derivatization and gas chromatography-mass spectrometry. The method development included the optimization of ultrasonic hydrolysis and extraction, screening of N-ethoxycarbonylation conditions with ethyl chloroformate, evaluation of the diamines degradation, and analysis of the fragmentation mechanisms. Under the optimum experimental conditions, good linearity was observed with R2 &gt; 0.999. The extraction recoveries were found in the range of 93.9&ndash;101.2% with repeatabilities and reproducibilities in 0.89&ndash;8.12% and 2.12&ndash;10.56%, respectively. The limits of detection ranged from 0.0025 to 0.057 &micro;g/mL. The developed method was applied to commercial polybutylene adipate co-terephthalate (PBAT) biodegradable mulch film samples for analysis of the diverse residual diisocyanates and related diamine additives. The components varied greatly among the sample from different origin. Overall, this study provides a reliable method for assessing safety in biodegradable mulch films