| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Li, Yuanzi, et al.
(författare)
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Optimization of the l-tyrosine metabolic pathway in Saccharomyces cerevisiae by analyzing p-coumaric acid production
- 2020
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Ingår i: 3 Biotech. - : Springer Science and Business Media LLC. - 2190-572X .- 2190-5738. ; 10:6
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we applied a series of genetic modifications to wild-type S. cerevisiae strain BY4741 to address the bottlenecks in the l-tyrosine pathway. A tyrosine ammonia-lyase (TAL) gene from Rhodobacter capsulatus, which can catalyze conversion of l-tyrosine into p-coumaric acid, was overexpressed to facilitate the analysis of l-tyrosine and test the strain's capability to synthesize heterologous derivatives. First, we enhanced the supply of precursors by overexpressing transaldolase gene TAL1, enolase II gene ENO2, and pentafunctional enzyme gene ARO1 resulting in a 1.55-fold increase in p-coumaric acid production. Second, feedback inhibition of 3-deoxy-d-arabino-heptulosonate-7-phosphate synthase and chorismate mutase was relieved by overexpressing the mutated feedback-resistant ARO4(K229L) and ARO7(G141S), and a 3.61-fold improvement of p-coumaric acid production was obtained. Finally, formation of byproducts was decreased by deleting pyruvate decarboxylase gene PDC5 and phenylpyruvate decarboxylase gene ARO10, and p-coumaric acid production was increased 2.52-fold. The best producer-when TAL1, ENO2, ARO1, ARO4(K229L), ARO7(G141S), and TAL were overexpressed, and PDC5 and ARO10 were deleted-increased p-coumaric acid production by 14.08-fold (from 1.4 to 19.71 mg L-1). Our study provided a valuable insight into the optimization of l-tyrosine metabolic pathway.
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| 3. |
- Song, Yanling, et al.
(författare)
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Growth of winter wheat adapting to climate warming may face more low-temperature damage
- 2023
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 43:4, s. 1970-9
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Tidskriftsartikel (refereegranskat)abstract
- China's surface air temperature is increasing due to global warming, so it is interesting that how low temperatures would be changed during the growth period of winter wheat in future. We focused on the low temperatures of winter wheat from 2021 to 2050, using temperatures under the high emission scenario Representative Concentration Pathway 8.5 (RCP8.5) projected by the RegCM4.4 regional climate model. The results showed that the annual mean temperature was projected to increase by 0.42°C⋅decade−1 in the northern and by 0.35°C⋅decade−1 in the southern winter wheat region. Furthermore, the temperature was expected to increase rapidly in spring, which could advance the dates of flowering and the start of the grain-filling period. Using the genetic parameters determined by the calibration and validation of WOFOST and bias-corrected projected meteorological data, simulations of winter wheat growth were performed over the winter wheat region for 2021–2050. The simulated number of days to the flowering period of winter wheat for 2041–2050 was on average 6.5 days less than in 2021–2030, due to the spring warming. Because of the earlier start of the growing season, winter wheat could face negative effects by being subjected to low temperatures. Indeed, the number of low-temperature days was projected to increase by 110% from 2041 to 2050 compared to 2021–2030, and the number of killing degree days (KDDs) is projected to increase by 120% at the same time. If the number of days to flowering did not change, the number of low-temperature days and KDDs only changed slightly, showing that the negative influence of low temperature was mainly caused by the advancement of the flowering date. The effect of low temperature on growth was underestimated when the response of winter wheat growth to global warming was not considered.
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| 4. |
- Song, Yanling, et al.
(författare)
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Rain-season trends in precipitation and their effect in different climate regions of China during 1961–2008
- 2011
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 6:3, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Using high-quality precipitation data from 524 stations, the trends of a set of precipitation variables during the main rain season (May–September) from 1961 to 2008 for different climate regions in China were analysed. However, different characteristics were displayed in different regions of China. In most temperate monsoon regions (north-eastern China), total rain-season precipitation and precipitation days showed decreasing trends; positive tendencies in precipitation intensity were, however, noted for most stations in this region. It is suggested that the decrease in rain-season precipitation is mainly related to there being fewer rain days and a change towards drier conditions in north-eastern China, and as a result, the available water resources have been negatively affected in the temperate monsoon regions. In most subtropical and tropical monsoon climate regions (south-eastern China), the rain-season precipitation and precipitation days (11–50, with > 50 mm) showed slightly positive trends. However, precipitation days with ≤ 10 mm decreased in these regions. Changes towards wetter conditions in this area, together with more frequent heavy rainfall events causing floods, have a severe impact on peoples' lives and socio-economic development. In general, the rain-season precipitation, precipitation days and rain-season precipitation intensity had all increased in the temperate continental and plateau/mountain regions of western China. This increase in rain-season precipitation has been favourable to pasture growth.
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| 5. |
- Song, Yanling, et al.
(författare)
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The contributions of climate change and production area expansion to drought risk for maize in China over the last four decades
- 2021
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 41:S1
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 The Authors International Journal of Climatology published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society. Maize is one of China's most important crops and is profoundly sensitive to drought. Using weather and county-level maize yield data, the drought risk for maize in China was estimated for the period 1971–2010. The results show that drought risk has increased in China over the last 40 years, and that areas experiencing moderate to high drought risk have expanded, particularly in Northeast China. The main reasons for the observed changes are increased drought hazard associated with climate change, and increased exposure of maize to drought due to an expanded production area. Drought risk over all of China increased by 55% in the 2000s compared to the 1970s. While around 93% of the increase in drought risk in the maize production regions is due to increased drought exposure, 7% is attributable to climate change. In Northeast China alone, drought risk increased by 129% from the 1970s to the 2000s, which is the sum of an 86% increase caused by greater drought exposure, associated with expansion of the production area, and a 14% increase driven by climate change. The results indicate that the drought hazard has increased by around 13%, and drought risk has increased by 110% for each 1°C rise in annual mean temperature in Northeast China over the past 40 years. Maize yield losses have increased by around 4% per 1°C increase in annual mean temperature in this region. The sensitivity of maize to drought means that climate change is likely to have significant negative impact on future maize productivity, and China's export and import of maize is likely to be affected.
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| 6. |
- Song, Yanling, et al.
(författare)
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The relative contribution of climate and cultivar renewal to shaping rice yields in China since 1981
- 2015
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Ingår i: Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 120:1-2, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Rice is one of China’s most important staple food crops, where the yields are strongly influenced by climate and rice variety renewal. Using high-quality weather data, rice growth, and agricultural practice data, the contribution of climatic variation on rice yield increases was analyzed from 1981 to 2009 inWuchang, Northeast China. In this region, the annual mean surface air temperature increased by 0.6 °C/decade, and the accumulated temperature (>10 °C) increased by 120.1 °C/ decade from 1981 to 2009, mainly related to global warming. During the same period, rice yields increased by 2,095 kg/ ha*decade. To quantify the contribution of climate change to rice yield increases, a “climate similarity index” was devised, where the most important climate parameters for rice growth were compared among years. If the rice variety was changed between 2 years, while the climate conditions were similar, any yield changewould be attributed to a rice variety renewal effect. Conversely, changes in rice yields that were not associated with variety changes were attributed to climate change. Our results showed that over the analyzed period, the influence of climate on yields was estimated to 805 kg/ha per decade, while the increasing trend due to rice variety renewal was estimated to 1,290 kg/ha per decade. Thus, 38 % of the yield increases can be related to climatic variation and the remaining 62 % to changes in rice varieties. Furthermore, the effect of variety renewal on the rice yield increases wasmore pronounced before the 1990s, while afterward, the yield increases were mainly influenced by climatic variations in Northeast China.
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| 7. |
- Yang, Ya, et al.
(författare)
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Human exposure to phthalate esters via ingestion of municipal drinking water from automatic water purifiers : levels, sources, and risks
- 2022
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Ingår i: Environmental Science. - : Royal Society of Chemistry. - 2053-1400 .- 2053-1419. ; 8:12, s. 2843-2855
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Tidskriftsartikel (refereegranskat)abstract
- The presence of organic pollutants in drinking water is an environmental problem threatening public health. Water purifiers are commonly recognized as effective purification equipment for drinking water and are thus prevalent in the market, so there is a need to assess their true effects on drinking water. In this study, we have analyzed the distribution, potential sources, and health risks of phthalate esters (PAEs) in tap as well as purified water. 7 out of 22 target PAEs have been detected in a total of 75 drinking water samples, including tap water (TW), water vending machines (WVMs), and water boiling machines (WBMs). The total concentrations of 22 PAEs are N.D. to 447 ng L-1 in TW samples, 25.7 to 1.10 x 10(3) ng L-1 in WBM water, and N.D. to 841 ng L-1 in WVM water. The concentrations of PAEs in most WVM and WBM samples were comparable or slightly higher than those in TW samples. Meanwhile, the sigma PAE concentrations in the nearshore of the Yangtze Estuary area (northern and southern areas) were slightly higher than those from offshore areas (Pudong: PD, Fengxian and Minhang: FM), which may be attributed to the source water. Combining the results of principal component analysis and correlation analysis, certain PAEs, e.g., diisobutyl phthalate (DIBP), dibuthyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP), were more polluting than diethyl phthalate (DEP) and di-methyl phthalate (DMP) in WVM water than those in TW samples. This work suggests that the application of water purifiers may not remove certain PAEs efficiently from drinking water. In addition, the estimated daily intakes (EDIs) of sigma PAE via drinking water from automatic water purifiers were 2-3 times those from tap water under a high-exposure scenario, but all EDIs are well below current health regulatory guidelines for PAEs. This survey indicates that water purifiers made nearly no decrease to the PAE concentrations and possibly have negative effects on the quality of drinking water.
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