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

Bilayer-favored intercalation induced efficient and selective liquid phase production of bilayer graphene

Bilayer graphene (BLG) is gaining increasing attention as one of the most promising candidate materials for post-silicon nanoelectronics. It is still a tremendous challenge to selectively and efficiently produce BLG at low cost and under mild conditions. Herein, a novel strategy of bilayer-favored intercalation (BFI) induced liquid phase exfoliation of BLG under mild conditions was developed. This simple approach can effectively exfoliate graphite to give BLG with a high yield of 52.3%, and selectivity as high as 86.5%. The obtained twisted BLG not only maintains the structural integrity and low surface oxidation of graphene, but also demonstrates great electron mobility. With careful experimental design and use of DFT calculations, such efficient production of BLG is proved to originate from the formation of a stage-two graphite intercalation compound via the bilayer-favored intercalation of chromyl chloride (CrO2Cl2) into graphite flakes driven by the electrostatic interactions between CrO2Cl2 and graphene sheets. The BFI-induced liquid phase exfoliation strategy shows great potential for the industrial scale production of high-quality BLG

Bilayer-favored intercalation induced efficient and selective liquid phase production of bilayer graphene

Bilayer graphene (BLG) is gaining increasing attention as one of the most promising candidate materials for post-silicon nanoelectronics. It is still a tremendous challenge to selectively and efficiently produce BLG at low cost and under mild conditions. Herein, a novel strategy of bilayer-favored intercalation (BFI) induced liquid phase exfoliation of BLG under mild conditions was developed. This simple approach can effectively exfoliate graphite to give BLG with a high yield of 52.3%, and selectivity as high as 86.5%. The obtained twisted BLG not only maintains the structural integrity and low surface oxidation of graphene, but also demonstrates great electron mobility. With careful experimental design and use of DFT calculations, such efficient production of BLG is proved to originate from the formation of a stage-two graphite intercalation compound via the bilayer-favored intercalation of chromyl chloride (CrO2Cl2) into graphite flakes driven by the electrostatic interactions between CrO2Cl2 and graphene sheets. The BFI-induced liquid phase exfoliation strategy shows great potential for the industrial scale production of high-quality BLG

New insights into the evolution and functional divergence of the SWEET family in Saccharum based on comparative genomics

Abstract Background The SWEET (Sugars Will Eventually be Exported Transporters) gene family is a recently identified group of sugar transporters that play an indispensable role in sugar efflux, phloem loading, plant-pathogen interaction, nectar secretion, and reproductive tissue development. However, little information on Saccharum SWEET is available for this crop with a complex genetic background. Results In this study, 22 SWEET genes were identified from Saccharum spontaneum Bacterial Artificial Chromosome libraries sequences. Phylogenetic analyses of SWEETs from 11 representative plant species showed that gene expansions of the SWEET family were mainly caused by the recent gene duplication in dicot plants, while these gene expansions were attributed to the ancient whole genome duplication (WGD) in monocot plant species. Gene expression profiles were obtained from RNA-seq analysis. SWEET1a and SWEET2s had higher expression levels in the transitional zone and maturing zone than in the other analyzed zones. SWEET1b was mainly expressed in the leaf tissues and the mature zone of the leaf of both S. spontaneum and S. officinarum, and displayed a peak in the morning and was undetectable in both sclerenchyma and parenchyma cells from the mature stalks of S. officinarum. SsSWEET4a\4b had higher expression levels than SWEET4c and were mainly expressed in the stems of seedlings and mature plants. SWEET13s are recently duplicated genes, and the expression of SWEET13s dramatically increased from the maturing to mature zones. SWEET16b’s expression was not detected in S. officinarum, but displayed a rhythmic diurnal expression pattern. Conclusions Our study revealed the gene evolutionary history of SWEETs in Saccharum and SWEET1b was found to be a sucrose starvation-induced gene involved in the sugar transportation in the high photosynthetic zones. SWEET13c was identified as the key player in the efflux of sugar transportation in mature photosynthetic tissues. SWEET4a\4b were found to be mainly involved in sugar transportation in the stalk. SWEET1a\2a\4a\4b\13a\16b were suggested to be the genes contributing to the differences in sugar contents between S. spontaneum and S. officinarum. Our results are valuable for further functional analysis of SWEET genes and utilization of the SWEET genes for genetic improvement of Saccharum for biofuel production

A robust and tunable Luttinger liquid in correlated edge of transition-metal second-order topological insulator Ta2Pd3Te5

Abstract The interplay between topology and interaction always plays an important role in condensed matter physics and induces many exotic quantum phases, while rare transition metal layered material (TMLM) has been proved to possess both. Here we report a TMLM Ta2Pd3Te5 has the two-dimensional second-order topology (also a quadrupole topological insulator) with correlated edge states - Luttinger liquid. It is ascribed to the unconventional nature of the mismatch between charge- and atomic- centers induced by a remarkable double-band inversion. This one-dimensional protected edge state preserves the Luttinger liquid behavior with robustness and universality in scale from micro- to macro- size, leading to a significant anisotropic electrical transport through two-dimensional sides of bulk materials. Moreover, the bulk gap can be modulated by the thickness, resulting in an extensive-range phase diagram for Luttinger liquid. These provide an attractive model to study the interaction and quantum phases in correlated topological systems

The evolutionary origin and domestication history of goldfish (Carassius auratus)

Goldfish have been subjected to over 1,000 y of intensive domestication and selective breeding. In this report, we describe a high-quality goldfish genome (2n = 100), anchoring 95.75% of contigs into 50 pseudochromosomes. Comparative genomics enabled us to disentangle the two subgenomes that resulted from an ancient hybridization event. Resequencing 185 representative goldfish variants and 16 wild crucian carp revealed the origin of goldfish and identified genomic regions that have been shaped by selective sweeps linked to its domestication. Our comprehensive collection of goldfish varieties enabled us to associate genetic variations with a number of well-known anatomical features, including features that distinguish traditional goldfish clades. Additionally, we identified a tyrosine-protein kinase receptor as a candidate causal gene for the first well-known case of Mendelian inheritance in goldfish-the transparent mutant. The goldfish genome and diversity data offer unique resources to make goldfish a promising model for functional genomics, as well as domestication