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

Bidirectional associations between e-cigarette use and alcohol use across adolescence

•E-cigarette use was positively associated with subsequent alcohol initiation.•The association of e-cigarette use with subsequent alcohol initiation was stronger for males.•Alcohol use was positively associated with subsequent e-cigarette initiation. Evidence on prospective bidirectional associations between e-cigarette and alcohol use among adolescents can inform prevention and policy but is largely absent from the literature. Data were drawn from a prospective cohort of students attending 10 Los Angeles high schools (N = 3396; baseline mean age = 14.1, SD = 0.4). Students completed surveys every 6-months from 2013 to 2017; 8 total waves. Analyses were restricted to (a) individuals who were never users of alcohol (N = 2394) or (b) individuals who were never users of e-cigarettes (N = 2704) at baseline. Repeated-measures, generalized linear mixed models were used to estimate the adjusted odds of past 6-month alcohol and e-cigarette initiation, in separate models. Among alcohol never-users at baseline, 15.7 % (N = 375) initiated alcohol use over the study period. Compared to never-users of e-cigarettes, those who reported use of e-cigarettes had 3.5 times the odds of subsequently initiating alcohol use in the following wave (OR = 3.54; 95 % CI: 2.81, 4.47). Stronger associations were observed for males (OR = 4.94; 95 % CI: 3.78, 6.45) than for females (OR = 3.21; 95 % CI: 2.33, 4.41; pinteraction = 0.04). Among e-cigarette never-users at baseline, 26.3 % (N = 709) initiated e-cigarette use over the study period. Compared to never-users of alcohol, those who reported use of alcohol had 3.2 times the odds of subsequently initiating e-cigarette use in the following wave (OR = 3.23; 95 % CI: 2.68, 3.89). This association did not differ by gender. E-cigarette and alcohol use can be markers to identify youth at risk for future alcohol and e-cigarette use, respectively. Research examining mechanisms underlying these associations is needed to infer causality

A mouse model of Zhu-Tokita-Takenouchi-Kim syndrome reveals indispensable SON functions in organ development and hematopoiesis

Rare diseases are underrepresented in biomedical research, leading to insufficient awareness. Zhu-Tokita-Takenouchi-Kim (ZTTK) syndrome is a rare disease caused by genetic alterations that result in heterozygous loss of function of SON. While patients with ZTTK syndrome live with numerous symptoms, the lack of model organisms hampers our understanding of SON and this complex syndrome. Here, we developed Son haploinsufficiency (Son+/–) mice as a model of ZTTK syndrome and identified the indispensable roles of Son in organ development and hematopoiesis. Son+/– mice recapitulated clinical symptoms of ZTTK syndrome, including growth retardation, cognitive impairment, skeletal abnormalities, and kidney agenesis. Furthermore, we identified hematopoietic abnormalities in Son+/– mice, including leukopenia and immunoglobulin deficiency, similar to those observed in human patients. Surface marker analyses and single-cell transcriptome profiling of hematopoietic stem and progenitor cells revealed that Son haploinsufficiency shifted cell fate more toward the myeloid lineage but compromised lymphoid lineage development by reducing genes required for lymphoid and B cell lineage specification. Additionally, Son haploinsufficiency caused inappropriate activation of erythroid genes and impaired erythropoiesis. These findings highlight the importance of the full gene expression of Son in multiple organs. Our model serves as an invaluable research tool for this rare disease and related disorders associated with SON dysfunction