Robust estimation of bacterial cell count from optical density

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

The Effect of Forest Growth Rate on Climate Change Impacts of Logging Residue Utilization

Biofuel is encouraged because of its low impact on climate change. A new framework was developed to accurately assess the climate change impacts (CCI) of biofuel by integrating the atmospheric carbon cycle model and vegetation carbon dynamic models. Forests with different growth rates (fast, medium, slow) and three collection intensities (71%, 52%, 32%) of logging residues were presumed to test the performance of this framework. The CCI of biofuel was analyzed under two functional units: 1 GJ of biofuels and 1 ha of forests to supply biofuels. According to this study, increasing the forest growth rate could decrease the CCI in both functional units. Increasing the collection intensity could decrease the CCI of 1 GJ of biofuel but increase the CCI of 1 ha of forest land (unless the impacts were negative in fast-growth forests with high and medium collection intensities). Producing bioethanol resulted in a lower CCI (−3.1–67.7 kg CO2 eq/GJ) compared to bio-diesel (29.3–94.7 kg CO2 eq/GJ). Hence, collecting all available logging residues (without inhibiting forest regrowth) to produce low CCI biofuels such as bioethanol was found to be the optimal option for achieving high mitigation effects

Simulation of solar radiation on ground surfaces based on 1 km grid-cells

Multivariate nonlinear regression model was established to simulate the solar radiation on level surface of 1 km grid-cells in China. The validation shows the prediction accuracy is 96.63 percent. Based on digital elevation model (DEM), the direct radiation ratios of slope to level and the sky view factors of slope were calculated respectively to modify direct and diffuse solar radiation which aimed to get the actual solar radiation on 1 km ground surfaces. The results indicated that great difference of solar radiation between slope and level surfaces existed in hill and mountainous regions, and the maximum difference might reach 67 percent in China. The simulated radiation could be used in extensive fields of agricultural practices and researches, such as assessment of agricultural potential productivity, agricultural zoning, distribution of crops, and returning farmland into forest and grassland

Extracellular vesicles derived from human umbilical cord mesenchymal stem cells alleviate osteoarthritis of the knee in mice model by interacting with METTL3 to reduce m6A of NLRP3 in macrophage

Abstract Background Osteoarthritis (OA) is a prevalent degenerative joint disease that not only significantly impairs the quality of life of middle-aged and elderly individuals but also imposes a significant financial burden on patients and society. Due to their significant biological properties, extracellular vesicles (EVs) have steadily received great attention in OA treatment. This study aimed to investigate the influence of EVs on chondrocyte proliferation, migration, and apoptosis and their protective efficacy against OA in mice. Methods The protective impact of EVs derived from human umbilical cord mesenchymal stem cells (hucMSCs-EVs) on OA in mice was investigated by establishing a mouse OA model by surgically destabilizing the medial meniscus (DMM). Human chondrocytes were isolated from the cartilage of patients undergoing total knee arthroplasty (TKA) and cultured with THP-1 cells to mimic the in vivo inflammatory environment. Levels of inflammatory factors were then determined in different groups, and the impacts of EVs on chondrocyte proliferation, migration, apoptosis, and cartilage extracellular matrix (ECM) metabolism were explored. N6-methyladenosine (m6A) level of mRNA and methyltransferase-like 3 (METTL3) protein expression in the cells was also measured in addition to microRNA analysis to elucidate the molecular mechanism of exosomal therapy. Results The results indicated that hucMSCs-EVs slowed OA progression, decreased osteophyte production, increased COL2A1 and Aggrecan expression, and inhibited ADAMTS5 and MMP13 overexpression in the knee joint of mice via decreasing pro-inflammatory factor secretion. The in vitro cell line analysis revealed that EVs enhanced chondrocyte proliferation and migration while inhibiting apoptosis. METTL3 is responsible for these protective effects. Further investigations revealed that EVs decreased the m6A level of NLRP3 mRNA following miR-1208 targeted binding to METTL3, resulting in decreased inflammatory factor release and preventing OA progression. Conclusion This study concluded that hucMSCs-EVs inhibited the secretion of pro-inflammatory factors and the degradation of cartilage ECM after lowering the m6A level of NLRP3 mRNA with miR-1208 targeting combined with METTL3, thereby alleviating OA progression in mice and providing a novel therapy for clinical OA treatment