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

Influence of the molecular structure of phenylamine antioxidants on anti-migration and anti-aging behavior of high-performance nitrile rubber composites

The structure of antioxidants significantly affects the anti-migration and thermal-oxidative aging properties of nitrile butadiene rubber (NBR) composites, which are crucial for applications in aerospace, biomedical, and fuel cell stack sealing industries. The findings reveal that the migration rate of N-(4-anilino phenyl) maleic imide (MC), with a reactive double bond, is only 15.6%, exhibiting the best extraction resistance. 2,4,6-Tris-(N-1,4-dimethylpentyl-p-phenylenediamino)-1,3,5-triazine (TMPPD), with a greater weight and dendritic structure, follows at 47.7%, while N-isopropyl-N′-phenyl-p-phenylenediamine (4010NA) performs the worst, with 77.8%. Furthermore, after thermal-oxidative exposure, the cross-link density of NBR composites increases, generating oxygenated substances, such as ethers, aldehydes, and acids. The addition of antioxidants in the composites improves the thermal-oxidative aging properties compared to those without any antioxidants. Moreover, antioxidants 4010NA and TMPPD display superior resistance to thermal-oxidative aging properties compared to antioxidant MC

Study on the life maintenance mechanism of Eisenia fetida under low-density polyethylene stress: Based on path analysis and canonical correlation analysis

The widespread use but low recovery rate of agricultural films has led to microplastic accumulation in farmlands, which poses a serious threat to the health of the soil ecosystem. There is an urgent need for early warning and monitoring of soil microplastics pollution, as well as the performance of bioremediation research. In this study, earthworms were used as test organisms to carry out toxicological tests under low-density polyethylene (LDPE) stress. A canonical correlation analysis model (CCA) was established to analyze the relationship between oxidative stress and microbial community. A path analysis model (PA) was also constructed to examine the detoxification mechanism of earthworms under LDPE stress. The results showed that low concentrations (100 and 500 mg/kg) of LDPE did not cause oxidative damage to earthworms but stimulated their physiological metabolism. Meanwhile, 1000 mg/kg LDPE concentrations caused oxidative damage to earthworms and altered their internal microbial community structure. Furthermore, at 1500 mg/kg LDPE concentrations, the oxidative stress to the earthworms is aggravated, and their physiological responses work in conjunction with the microbial community to cope with the adverse condition. Lastly, treatment with 2000 mg/kg LDPE induced the appearance of LDPE tolerant populations in the microbial community in vivo. Taken together, our results provide a theoretical basis for revealing the physiological response of earthworms when challenged in a polluted environment and provide a model for pollution remediation and ecological security monitoring of soil ecosystems