Cell Length Research Articles

Covalent labeling of the Arabidopsis plasma membrane H+-ATPase reveals 3D conformational changes involving the C-terminal regulatory domain.

The plasma membrane proton pump is the primary energy transducing, electrogenic ion pump of the plasma membrane in plants and fungi. Compared to its fungal counterpart, the plant plasma membrane proton pump's regulatory C-terminal domain (CTD) contains an additional regulatory segment that links multiple sensory pathways regulating plant cell length through phosphorylation and recruitment of regulatory 14-3-3 proteins. However, a complete structural model of a plant proton pump is lacking. Here, we performed covalent labeling with mass spectrometric analysis (CL-MS) on the Arabidopsis pump AHA2 to identify potential interactions between the CTD and the catalytic domains. Our results suggest that autoinhibition in the plant enzyme is much more structurally complex than in the fungal enzyme.

Contrasting strategies in morphological and physiological response to drought stress among temperate forest understory forbs and graminoids.

Drought stress can profoundly affect plant growth and physiological vitality, yet there is a notable scarcity of controlled drought experiments focused on herbaceous species of the forest understorey. In this study, we collected seeds from five forb and four graminoid species common in European temperate forests. Seeds were germinated under controlled glasshouse conditions and subjected to moderate drought stress for 5 weeks. We assessed biomass partitioning, stomatal and leaf morphology, leaf gas exchange, minimum leaf conductance (gmin), and chlorophyll fluorescence parameters. Comparison of the two ecological guilds revealed that graminoids had a higher R/S, improved WUE, greater carboxylation efficiency, and enhanced non-photochemical quenching under drought conditions compared to forbs. In contrast, forbs had significantly lower gmin, with higher total biomass and total leaf area. Despite these differences in morpho-physiological functional traits, both groups experienced a similar relative reduction in biomass after drought stress. Key predictors of biomass accumulation under drought included photochemical quenching, stomatal traits, total leaf area and gmin. A negative correlation between biomass and gmin suggests that plants with lower residual water loss after stomatal closure can accumulate more biomass under drought stress. Additionally, gmin was positively correlated with guard cell length, suggesting that larger stomata contribute to higher residual water loss. Contrasting strategies in morpho-physiological responses to drought define the differences between the two groups. In graminoids, drought resistance suggests greater emphasis on stress tolerance as a survival strategy. In contrast, forbs were able to maintain higher biomass and total leaf area, indicating a competitive strategy for maximizing resource acquisition.

Effects of ploidy level on leaf morphology, stomata, and anatomical structure of Hibiscus syriacus L.

BackgroundHibiscus syriacus L. is a deciduous shrub with a strong environmental resistance and wide application prospects. The genetic background and ploidy levels of Hibiscus cultivars are complex, and polyploid breeding has long been an important method for developing new Hibiscus cultivars. However, the relationship of ploidy levels with leaf morphology, stomatal characteristics, and leaf anatomy remains unclear.ResultsThis study analyzed three ploidy levels (triploid, tetraploid, and hexaploid) of Hibiscus syriacus. Flow cytometry confirmed the ploidy levels, and morphological traits were evaluated. Leaf length, leaf width, and petiole length decreased with increasing ploidy. Stomatal length, stomatal width, guard cell length, and guard cell width increased and stomatal number and density decreased with increasing ploidy. The hexaploids exhibited the highest midrib diameter and palisade tissue thickness values. Correlation analyses revealed that stomatal morphology served as a reliable marker for determining ploidy levels.ConclusionThis study highlights the impact of varying ploidy levels on the leaf and stomatal morphologies and leaf anatomy of Hibiscus syriacus. These findings can provide theoretical guidance for improving Hibiscus cultivars in terms of stress resistance, adaptability, and ornamental traits, and for developing new cultivars with enhanced characteristics. Future research should focus on utilizing these morphological markers to optimize breeding strategies for Hibiscus cultivars.

Transcription factor AP-4 reactivates telomerase reverse transcriptase independently of genome alteration in non-HBV associated hepatocellular carcinoma

Recurrent genome alterations have been identified in the telomerase reverse transcriptase (TERT) promoter region, a common occurrence in various types of cancer. In addition to epigenetic alterations at the TERT promoter region, the recruitment of transcription factors to this region, which potentially drives the reactivation of TERT gene transcription in human hepatocellular carcinoma (HCC) remains unknown. In this study, using in-silico DNA binding sequence analysis at the TERT promoter and with confirmation with dual luciferase reporter and chromatin immunoprecipitation assays, we found that Transcription Factor AP-4 (TFAP4) physically interacted with the TERT promoter, driving telomerase reactivation. Furthermore, TFAP4 mRNA is upregulated in human HCCs and positively correlates with TERT mRNA expression, according to TCGA-LIHC database, our in-house clinical samples, and HCC cell lines. Interestingly, the knockdown of TFAP4 only suppressed TERT expression levels and telomere length in HCC cells which are not associated with HBV infection. Additionally, we identified that the CCCTC-binding factor (CTCF) physically interacted with the TFAP4 promoter, leading to induced TFAP4 gene transcription in HCC. Clinically, TFAP4 mRNA expression significantly correlated with TERT mRNA expression in alcohol-related HCCs, but not in HBV-associated HCCs, according to TCGA-LIHC cohort. Consistently, ethanol enhanced both TFAP4 and TERT mRNA expression in non-HBV-associated HCC cells but not HBV-associated HCC cells. In conclusion, our findings demonstrate that TFAP4 directly regulates TERT gene transcription via CTCF in non-HBV-associated HCCs. However, its role in regulating telomerase expression or activity through HBV DNA integration in HBV-associated cells might be limited.

Variation in the Morphological Characters of the Hill and Plain Populations of Indian Honey Bee, Apis cerana indica (Fab.) in Tamil Nadu, India

The present study investigates the morphological differences between the hill and plain populations of the Indian honey bee, Apis cerana indica Fabricius, collected from six different locations in Tamil Nadu, India: Coimbatore, Karumandhurai, Coonoor, Madurai, Dindigul, and Chidambaram during 2023-2024. Significant differences were found between the two populations based on a comprehensive morphometric analysis of 29 characters. The hill populations from TNAU Insectary (Marudhamalai hills), Karumandhurai (Kalvarayan hills), and Coonoor (Nilgiri hills), the mean altitude of the locations being 1207 m a.s.l. exhibited significantly higher values in several morphometric traits than the plain populations from Madurai, Dindigul, and Chidambaram, with a mean altitude of 124 m above MSL (P<0.05). Component loading analysis highlighted the key morphometric characters contributing to the first and second components of both ecotypes. In the plain population, breadth of the radial cell, breadth of the forewing, and length of the radial cell demonstrated strong positive correlations with the first principal component, explaining 16.4% of the variance. The second principal component, influenced by characters such as the length of the femur and breadth of the metatarsus, showed 12.2% of the variance. In the hill population, the length of the radial cell, length of vein R.L., and length of the hindwing were the most influential traits for the first principal component, explaining 28.0% of the variance. In contrast, the second component, which included the breadth of the forewing and length of vein I.L., explained 12.3% of the variance. Further, the cubital index, a critical morphometric parameter, also showed a statistically significant difference, with the hill population (3.55) showing a higher value than the plain population (3.29). The significant morphometric differences observed between the hill and plain populations of A. cerana indica may suggest that they have undergone morphological divergence, likely due to adaptations to their specific environmental conditions.

Regulation of cochlear hair cell function by intracellular calcium stores

IntroductionMammalian hearing depends on the dual mechanosensory and motor functions of cochlear hair cells. Both these functions may be regulated by Ca2+ release from intracellular stores. However, it is still unclear how exactly intracellular Ca2+ release may affect either hair cell mechano-electrical transduction (MET) or prestin-dependent electromotility in outer hair cells (OHCs).MethodsHere, we used photo-activatable (caged) compounds to generate fast increases of either Ca2+ or inositol-3-phosphate (IP3) in the cytosol of young postnatal rodent auditory hair cells, thereby stimulating either Ca2+- or IP3- induced releases of Ca2+ from intracellular stores. Fast Ca2+ imaging was used to monitor propagation of Ca2+ signals along the length of a hair cell. To access potential physiological role(s) of intracellular Ca2+ releases, we used whole cell patch clamp to record: i) OHC voltage-dependent capacitance, a known electrical correlate of prestin-based electromotility, and ii) MET currents evoked by stereocilia bundle deflections with fluid-jet. In the latter experiments, changes of mechanical stiffness of the hair bundles were also quantified from video recordings of stereocilia movements.ResultsCa2+ uncaging at the OHC apex initiated Ca2+ wave propagating to the base of the cell with subsequent Ca2+ build-up there. Ca2+ uncaging at the OHC base generated long-lasting and apparently self-sustained Ca2+ responses, further confirming Ca2+-induced Ca2+ release in the OHC basal region. Photoactivated IP3 initiated a slow increase of cytosolic Ca2+ ([Ca2+]i) throughout the whole OHC, confirming the presence of slow-activated IP3-gated Ca2+ stores in OHCs. Interestingly, Ca2+ uncaging produced no effects on OHC voltage-dependent capacitance. In an OHC, the rise of [Ca2+]i is known to decrease axial stiffness of the cell and may modulate the stiffness of mechanosensory stereocilia bundles. To separate these two phenomena, we explored the potential effects of intracellular Ca2+ release on mechanical properties of stereocilia bundles in cochlear inner hair cells (IHCs). Ca2+ uncaging at the apex of an IHC caused a long-lasting increase in mechanical stiffness of stereocilia bundle without any changes in the amplitude or deflection sensitivity of the MET current.DiscussionWe concluded that the most likely physiological role of IP3-gated Ca2+ release at the apex of the cell is the regulation of hair bundle stiffness. In contrast, Ca2+-induced Ca2+ release at the base of OHCs seems to regulate axial stiffness of the cells and its hyperpolarization in response to efferent stimuli, without direct effects on the OHC prestin-based membrane motors.

Detailed thermo-hydraulic investigation of 3D octet lattice structure integrated heat sink

The present research work examined the thermo-fluidic characteristics of a heat sink packed with octet-structured periodic metal foam having varying porosity (0.83–0.93) and unit cell lengths (UCL) of 2.5–5 mm for electronic cooling application. AlSi10Mg material is considered for the octet lattice structure with water as the cooling medium, with the inlet velocity ranging from 0.02 to 0.05 m/s and a steady heat flux of 10 W/cm2 applied at base of the substrate. The effect of the porosity, unit cell length, and inlet velocity on pressure gradient, friction factor, Nusselt number, wall temperature, heat transfer coefficient, and thermo-hydraulic performance parameter is analyzed. Larger pressure gradients are observed for lower values of porosity and unit cell length, with a maximum value of approximately 5000 Pa/m for the thermal system having 0.83 porosity, 2.5 mm UCL, and 0.05 m/s inlet velocity. The wall temperature drops with a rise in inlet velocity and a reduction in porosity and UCL, with the lowest value of 311 K for the case of 0.83 porosity, 2.5 mm UCL, and 0.05 m/s inlet velocity. The case of 0.83 porosity, 5 mm UCL, and 0.02 m/s velocity was determined as optimum design based on thermo-hydraulic performance parameter.

The Effects of Dexamethasone on Human Lens Epithelial Cells and the Analysis of Related Pathways with Transcriptome Sequencing.

The goal of this study was to investigate the effects of dexamethasone on human lens epithelial cells (HLECs) and the potential mechanisms. HLECs (HLE-B3) were cultured in vitro to assess the effects of dexamethasone on cell size at different concentrations. Immunofluorescence staining was used to detect specific protein expression in HLE-B3 cells. The cell size was observed using phase-contrast microscopy, and the length and area were quantitatively measured with ImageJ software for statistical analysis. Flow cytometry was used to verify these outcomes. The means of three groups were statistically analyzed using one-way analysis of variance, whereas the means of two groups were statistically analyzed with the parametric Student's t-test. Additionally, high-throughput transcriptome sequencing was performed to compare messenger RNA (mRNA) expression levels between different concentrations of dexamethasone treatment groups and the control group, to identify potential signaling pathways. Subsequently, we performed quantitative Polymerase Chain Reaction (qPCR), immunofluorescence staining, and molecular docking experiments on the key differentially expressed genes. Dexamethasone affected the size of HLE-B3 cells. Both 0.25 and 0.5 μmol/L dexamethasone increased cell length and area, exhibiting no significant difference between the two treatment groups. Flow cytometry showed that dexamethasone increased cell size and granularity, with 0.25 μmol/L dexamethasone leading to larger cell areas and higher intracellular granularity. High-throughput transcriptome sequencing revealed significant upregulation of lysophosphatidic acid receptor 1 (LPAR1) and the pathways related to the glucocorticoid (GC) receptor. Certain concentrations of dexamethasone impact the morphology and biological functions of HLECs. As a subtype of G protein-coupled receptors, LPAR1 on the cell membrane may interact with dexamethasone, affecting cell size and inhibiting autophagy via the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway. These discoveries offer crucial biological insights into how dexamethasone influences the morphology and function of HLECs and the pathogenesis of GC-induced cataracts, offering potential molecular targets for future therapeutic strategies.

Comparative Analysis of Mesocotyl Elongation Ability among Maize Inbred Lines.

Mesocotyl plays a key role in the seedling emergence of maize; however, the mechanism of mesocotyl elongation is still unclear. Moreover, different maize inbred lines and cultivars have varied mesocotyl lengths positively correlated with deep sowing tolerance. In this study, we selected one inbred line with long mesocotyl (LM) and two maize inbred lines with short mesocotyl (SM1 and SM2) from more than 400 maize inbred lines. The mesocotyl length of the LM line was about three-fold longer than those of the SM1 and SM2 lines. Microstructure observation showed that the reason for short mesocotyl in the SM1 and SM2 lines was few cell numbers and short cell length, respectively. Subsequently, we used RNA-seq to investigate the mechanism of mesocotyl elongation by regulating cell number and cell length at the transcriptome level. Compared with the LM line, the SM1 line displayed stronger downregulation of Cytochrome P450 and peroxidase genes than the SM2 line. Moreover, plant hormone signal transduction plays a vital role in mesocotyl elongation. Taken together, we propose a model for mesocotyl elongation of maize inbred lines with different cell lengths and cell numbers, which provide new insights into mesocotyl elongation in maize.

Effects of particulate air pollution on BPDE-DNA adducts, telomere length, and mitochondrial DNA copy number in human exhaled breath condensate and BEAS-2B cells

Traffic-related particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) have been linked to respiratory diseases and cancer risk in humans. Genomic damage, including benzo[a]pyrene diolepoxide (BPDE)-DNA adducts as well as alterations in telomere length (TL) and mitochondrial DNA copy number (mtDNA-CN) are associated with respiratory diseases. This study aimed to investigate the association between exposure to traffic-related particulate pollutants and genomic damage in exhaled breath condensate (EBC) in human subjects and a bronchial epithelial cell line (BEAS-2B). Among the 60 healthy recruited subjects, residents living in high-traffic-congested areas were exposed to higher concentrations of PM2.5 (1.66-fold, p < 0.01), UFPs (1.79-fold, p < 0.01), PM2.5-PAHs (1.50-fold, p < 0.01), and UFPs-PAHs (1.35-fold, p < 0.05), than those in low-traffic-congested areas. In line with increased exposure to particulate air pollution, the high-traffic-exposed group had significantly increased BPDE-DNA adducts (1.40-fold, p < 0.05), TL shortening (1.24-fold, p < 0.05), and lower mtDNA-CN (1.38-fold, p < 0.05) in EBC. The observations in the human study linking exposure to PM2.5, UFPs, PM2.5-PAHs, and UFPs-PAHs with the aforementioned biological effects were confirmed by an in vitro cell-based study, in which BEAS-2B cells were treated with diesel exhaust particulate matter (DEP) containing fine and ultrafine PM and PAHs. Increased BPDE-DNA adducts levels, shortened TL, and decreased mtDNA-CN were also found in treated BEAS-2B cells. The shortened TL and decreased mtDNA-CN were in part mediated by decreased transcript levels of hTERT, and SIRT1, which are involved in telomerase activity and mitochondrial biogenesis, respectively. These results suggest that exposure to traffic-related particulate pollutants can cause genomic instability in respiratory cells, which may increase the health risk of respiratory diseases and the development of cancer.

Anatomical-Foliar Diversity of Agave salmiana subsp. salmiana (Asparagaceae) in Three Populations of the Teotihuacán Region (Mexico).

Agave salmiana Otto ex Salm-Dyck is an endemic Mexican plant distributed from 1230 to 2460 m above sea level, native to the arid zones of central and southern Mexico. It is a traditionally used species, with morphotypes ranging from wild to cultivated, with an ample cultural and management history. The species is important because it generates employment, and its products are used for self-consumption and are marketed as raw materials; however, little is known about its leaf anatomical description or studies that report the variation in its characters in terms of its level of management and its altitudinal gradient. To address this, we collected leaf samples from three localities of the Teotihuacan region in the State of Mexico (Mexico) and obtained anatomical leaf sections; with these, we also obtained thirty-eight parameters to quantitatively describe leaf anatomy. Thus, in this study, the general anatomical description of the leaf of Agave salmiana subsp. salmiana is presented. Unique leaf characters and others shared with the species of the genus were identified for the leaf of A. salmiana subsp. salmiana. In addition, significant variation was observed when comparing the three sampled localities (78.95%). From the analysis of anatomical characters, abaxial outer periclinal wall length, length of adaxial palisade parenchyma cells, fiber length, surface area of abaxial epidermal cells, width of abaxial palisade parenchyma cells, and total length of parenchyma in adaxial palisade were found to distinguish individuals from the three localities analyzed and the differences are related to management and altitude gradients.

OsABT Negatively Regulates the Abscisic Acid Signal Transduction Pathway in Rice Seedling Roots

Rice (Oryza sativa L.) is a main food crop in China and is crucial for the maintenance of national food security. The growth of rice seedling roots is regulated by a variety of genes and is closely related to abscisic acid (ABA) metabolism and ABA signaling pathways. In this study, we found that OsABT could increase the length of rice root tip meristem cells and upregulate root development-related genes, thereby alleviating ABA’s inhibitory effects on rice root growth and seed germination. The overexpression of OsABT reduced the ABA content by downregulating ABA synthesis genes (OsNCED3 and OsNCED5) and upregulating the ABA catabolic gene (OsABA8ox2). In addition, OsABT interacted with OsPYL4, OsPYL10, and OsABIL2 via the ABA signal transduction pathway. By inhibiting the expression of positive regulatory genes (OsPYL9 and Rab16a) and increasing the expression of a negative regulatory gene (OsABIL1), OsABT negatively regulates the ABA signal transduction pathway. Transcriptome analysis revealed that OsABT inhibited the activity of Gene Ontology entries in response to ABA. Thus, OsABT increased the length of the rice root meristem, reduced the accumulation of ABA in the roots, and negatively regulated the ABA signal transduction pathway by interacting with key proteins in this pathway, ultimately relieving the inhibitory effect of ABA on rice root length and seed germination.

N6-Methyladenosine Regulates Cilia Elongation in Cancer Cells by Modulating HDAC6 Expression.

Primary cilia are microtubule-based organelles that function as cellular antennae to address multiple metabolic and extracellular cues. The past decade has seen significant advances in understanding the pro-tumorigenic role of N6-methyladenosine (m6A) modification in tumorigenesis. Nevertheless, whether m6A modification modulates the cilia dynamics during cancer progression remains unclear. Here, the results show that m6A methyltransferase METTL3regulates cilia length in cancer cells via HDAC6-dependent deacetylation of axonemal α-tubulin, thereby controlling cancer development. Mechanically, METTL3 positively regulates the translation of HDAC6 in an m6A-dependent manner, while m6A methylation of A3678 in the coding sequence (CDS) of HDAC6 ameliorates its translation efficiency via facilitating the binding with YTHDF3. The upregulation of HDAC6 induced by METTL3 over-expression is capable of inhibitingcilia elongation and acetylation of α-tubulin, thereby shortening cilia length and accelerating the progression of cervical cancer both in vitro and in vivo. Collectively, depletion of METTL3-mediated m6A modification leads to abnormally elongated cilia via suppressing HDAC6-dependent deacetylation of axonemal α-tubulin, ultimately attenuating cell growth and cervical cancer development.

Modeling of intermodulation in a loaded-line phase shifter based on a polynomial varactor model

Abstract This paper investigates if there is an optimum design of loaded-line phase shifters with respect to phase shift/loss figure of merit (FOM) and linearity. The investigation was performed by comparing six loaded-line phase shifters that were implemented in printed circuit board (PCB)technology with shunt-loaded hyperabrupt varactor-diodes. It was demonstrated that the hyperabrupt varactor’s C-V characteristics must be modeled with high accuracy to predict the nonlinear behavior. A polynomial varactor model was employed and experimentally validated. To extend the range of investigated parameter values, the extracted model was scaled and evaluated further in a circuit simulator. The investigation reveals that for a given varactor-capacitance, the phase shift/loss FOM is improved if the varactor-capacitance is evenly distributed and the unit cell length is much shorter than a quarter wavelength. The study demonstrates that the phase shift/loss depends mainly on the distribution of varactor-capacitance and Q factor. The intermodulation (IM) distortion is primarily proportional to the total varactor-capacitance per unit cell. The study also revealed that an increase in the varactor’s Q factor results in higher IM. Therefore, it is a trade-off between low loss and low IM.

Measuring Cell Dimensions in Fission Yeast Using Machine Learning.

In fission yeast (Schizosaccharomyces pombe), cell length is a crucial indicator of cell cycle progression. Microscopy screens that examine the effect of agents or genotypes suspected of altering genomic or metabolic stability and thus cell size are crucial for studying disruptions to cell cycle dynamics. This method is based on using an automated cell segmentation algorithm to measure S. pombe cells imaged by brightfield (BF) microscopy methods. PhotoPhenosizer (PP) is a machine learning-based tool designed for automated cell measuring and dimensional analysis of morphology frequency distributions. Integration of this method into large-scale pipelines for tracking cell dimension change streamlines morphological measurements, which facilitates the examination of cellular responses to genomic and metabolic stresses. In this protocol, we use PP to observe the effect of genomic instability on cell size dynamics over a 12-day chronological lifespan assay. Our results show that relative to wild-type cells, a replication stress mutant shows larger cells during chronological aging in excess glucose media. Our results are consistent with activation of checkpoints that regulate cell morphology in response to DNA damage. This method's application highlights the relevance of its incorporation in experimental routines that require large-scale image processing and its adoption by users with routine needs in S. pombe molecular research projects.

High-Throughput Measurement of Single-Fission Yeast Cell Volume Using Fluorescence Exclusion.

Cell volume is a critical parameter for the biology of living species and has an impact on virtually all cellular functions. In Schizosaccharomyces pombe, the regulation of cell size has been the focus of intense investigation, and mechanisms that couple size control with cell cycle progression have been identified. In fission yeast, cell length at division is generally used as a proxy for determining cell size. However, it only allows for an inaccurate evaluation of this critical parameter and neglects potential changes in cell morphology and diameter, which can strongly impact cell volume. Until recently, one of the major obstacles for studying the complexity of cell size regulation in fission yeast has been the lack of a robust method for high-throughput, direct measurement of single-cell volume. Here, we provide a comprehensive protocol for S. pombe cell volume determination based on the Fluorescence eXclusion method and microfluidics technologies. This approach makes it possible to reliably describe cell volume and its distribution in populations of fission yeast cells.

A Rapidly Inducible DNA Double-Strand Break to Monitor Telomere Formation, DNA Repair, and Checkpoint Activation.

The study of processes that govern genome integrity has been augmented by the ability to create a precise DNA double-strand break (DSB) in a short period of time that allows the kinetics of DNA metabolism and protein recruitment to be followed. Defined DSBs are made by expressing endonucleases with long recognition sites that are rare or absent in the genome, and require that the endonuclease is only active when induced. Research in this area in Schizosaccharomyces pombe was limited because rapidly inducible promoters were not available until around 2005, and several rapidly inducible DSB systems are now available. Here, we describe a system to rapidly induce a modified I-SceI endonuclease that can generate a DSB 20min after induction. I-SceI has no recognition sites in the S. pombe genome, allowing the introduction of complex substrates to monitor the effects of a new DSB in real time. This chapter describes how I-SceI can be most efficiently induced and a simple cell length measurement assay to monitor cell cycle checkpoint activation from a single DSB.

Novel Populations of Mycobacterium smegmatis Under Hypoxia and Starvation: Some Insights on Cell Viability and Morphological Changes.

The general features of the shift to a dormant state in mycobacterial species include several phenotypic changes, reduced metabolic activities, and increased resistance to host and environmental stress conditions. In this study, we aimed to provide novel insights into the viability state and morphological changes in dormant M. smegmatis that contribute to its long-term survival under starvation or hypoxia. To this end, we conducted assays to evaluate cell viability, morphological changes and gene expression. During starvation, M. smegmatis exhibited a reduction in cell length, the presence of viable but non-culturable (VBNC) cells and the formation of anucleated small cells, potentially due to a phenomenon known as reductive cell division. Under hypoxia, a novel population of pleomorphic mycobacteria with a rough surface before the cells reached nonreplicating persistence 1 (NRP1) was identified. This population exhibited VBNC-like behaviour, with a loss of cell wall rigidity and the presence of lipid-body-like structures. Based on dosR and hspX expression, we suggest that M. smegmatis encounters reductive stress conditions during starvation, while lipid storage may induce oxidative stress during hypoxia. These insights into the heterogeneous populations presented here could offer valuable opportunities for developing new therapeutic strategies to control dormant mycobacterial populations.

Progressive decline in old pole gene expression signal enhances phenotypic heterogeneity in bacteria.

Cell growth and gene expression are heterogeneous processes at the single-cell level, leading to the emergence of multiple physiological states within bacterial populations. Aging is a known deterministic driver of growth asymmetry; however, its role in gene expression heterogeneity remains elusive. Here, we show that aging mother cells undergo a progressive decline in old pole activity, generating asymmetry in protein partitioning, gene expression, and cell morphology. We demonstrate that mother cells, when compared to their daughters, exhibit lower product inheritance and gene expression rates independently of promoter dynamics. The declining activity of maternal old poles generates gene expression gradients that manifest as mother-daughter asymmetry upon division, showing that asymmetry is progressively built over time within the maternal intracellular environment. Moreover, old pole aging correlates with a gradual increase in cell length, leading to morphological asymmetry. These findings provide further evidence for aging as a mechanism to enhance phenotypic heterogeneity in bacterial populations, with possible consequences for stress response and survival.

Blast resistance analysis of butterfly-like reentrant circular honeycomb sandwich structure

Negative Poisson honeycomb has great potential in the field of protection against explosive shock due to its unique tensile expansion characteristics and excellent energy absorption capacity. However, there are limitations in the types and performance enhancement of the current negative Poisson honeycomb sandwich structure (HSS), so to further improve the blast resistance of conventional HSS and reduce the mass of the structures, a butterfly-type reentrant circular HSS is designed in this paper. In this analysis, the JC constitutive model related to the mechanical properties of AL-6XN304 alloy steel was used for simulation, and the explosion load was applied to the sandwich structure using the CONWEP loading mode in ABAQUS, and its explosion process was analyzed numerically in detail. Explosive simulation of square-core HSS is first performed, and the precision of the numerical model is verified by comparing it with the experimental result in the existing literature. Secondly, the dynamic response of the imitation butterfly-type HSS under air loading was investigated, and the blast resistance performance of this structure was compared with that of four HSSs under the same air loading. The effects of explosive mass, cell thickness, cell wall radius, and cell length parameters on the blast resistance of imitation butterfly-type reentrant circular sandwich structure were also explored. Findings indicate that the dynamic response of the butterfly-like reentrant circular HSS is divisible into three distinct phases: core compression, overall deformation, and equilibrium vibration. Compared with the square, circular, reentrant hexagonal, and star HSSs, the center displacement of the front panel of the structure is 22.4, 20.2, 8.8, and 23.0% lower, respectively, and the center displacement of the rear panel is 24.4, 20.6, 7.1, and 8.2% lower, respectively. In addition, the central area of the structure is also the lowest deflection. Therefore, the butterfly-like reentrant circular HSS has the best explosion resistance. The butterfly-like reentrant circular HSS of the front and rear panel deflection and the displacement at the center point escalates as the explosive mass grows, diminishes with the thickening of the cell wall, lessens as the radius of the cell wall shrinks, and lessens as the cell length shortens, the blast resistance of the structure can be further improved.