bluuebunny/crossref_metadata_2025 huggingface dataset:
Differences in Changes of Mobility Patterns Across the Globe—Evidence From a Natural Experiment
Authors: Kamińska Joanna A. , Kazak Jan K.
Published: October 2024

The impact of population mobility and transportation choices on the environment is significant. Sustainable mobility policies require an understanding of evolving mobility patterns. This study examines global mobility variations across countries using COVID‐19 Community Mobility Reports. Employing the k‐medoids algorithm and Dynamic Time Warping, we analyzed mobility dynamics. Results reveal diverse changes in population mobility. Around 52 Global North countries exhibit approximately 10% reduction in professional activity‐related traffic post‐COVID‐19. Regarding urban green space mobility, only 29 countries exhibit strong seasonality, with summer traffic in the northern hemisphere peaking at about 150% higher than winter traffic. Three groups of countries are identified concerning public transport mobility: returning to pre‐pandemic levels, experiencing a 25% increase, and nearly doubling from pre‐pandemic levels. This underscores the key determinants for sustainable mobility policy implementation. Fifteen highly developed countries share similar mobility patterns across six areas studied, facilitating the exchange of sustainable mobility solutions and best practices. This research underscores the importance of understanding and addressing evolving mobility patterns for effective environmental policy planning.
SHORT‐ROOT specifically functions in the chalazal region to modulate assimilate partitioning into seeds
Authors: Li Meng , Li Qianfang , Li Shuang , Niu Xufang , Xu Huimin , Li Pengxue , Bian Xinxin , Chen Zhichang , Liu Qian , Zhang Hongxiang , Liu Yunqi , Wu Shuang
Published: October 2024

Nourishing the embryo with endosperm and enclosing both embryo and endosperm in the seed coat are two important evolutionary innovations. Seed coat is conventionally viewed as a protective layer that functions after the seed has matured. Here, we challenge this notion by showing that a subregion of the seed coat, termed the chalazal seed coat (CZSC), is geared to gate seed nutrition loading in developing seeds. The CZSC develops the coordinative system comprising the apoplastic isolation, mediated by the restricted suberization, and the active transport, mediated by the specific expression of a variety of transporters, at as early as the globular embryo stage in both Arabidopsis and soybean seeds. This coordinated system in the CZSC disrupts the vascular continuum to the maternal tissues and forces the nutrient transport into selective and active absorption. We further reveal that the precision of the spatiotemporal suberin deposition and transporter expression is controlled by the regulatory hierarchy of SHR‐MYBs cascades. Our results provide a mechanistic insight into the assimilate accumulation in dicot seeds.
Myosin‐binding protein 13 mediates primary seed dormancy via abscisic acid biosynthesis and signaling in Arabidopsis
Authors: Hao Cui‐Hong , Pang Chen , Yang Li‐Na , Xiong Feng , Li Sha
Published: October 2024

Dormancy is an essential characteristic that enables seeds to survive in unfavorable conditions while germinating when conditions are favorable. Myosin‐binding proteins (MyoBs) assist in the movement of organelles along actin microfilaments by attaching to both organelles and myosins. In contrast to studies on yeast and metazoans, research on plant MyoBs is still in its early stages and primarily focuses on tip‐growing cells. In this study, we found that Arabidopsis MyoB13 is highly expressed in dry mature seeds. The myob13 mutant, created using CRISPR/Cas9, exhibits a preharvest sprouting phenotype, which can be mitigated by after‐ripening treatment, indicating that MyoB13 plays a positive role in primary seed dormancy. Furthermore, we show that MyoB13 negatively regulates ABA biosynthesis and signaling pathways. Notably, the expression of MyoB13 orthologs from maize and soybean can completely restore the phenotype of the Arabidopsis myob13 mutant, suggesting that the function of MyoB13 in ABA‐induced seed dormancy is evolutionarily conserved. Therefore, the functional characterization of MyoB13 offers an additional genetic resource to help prevent vivipary in crop species.
Improved Prediction of Pump Performance Through the Rotation–Curvature Correction—An Experimental and Numerical Study of a Low-Specific-Speed Helico-Axial Compression Cell in Series
Authors: Gundersen Ted Ø. S. , Torbergsen Erik A. , Balakin Boris , Arntzen Bjørn J. , Hoffmann Alex C.
Published: October 2024

Within turbomachines, turbulence production and redistribution are affected by system rotation and streamline curvature. However, the most frequently used turbulence models do not account for these effects. In the present paper, we calibrate a rotation–curvature correction to the shear stress transport (SST) turbulence model to improve the accuracy of pump performance predictions through computational fluid dynamics (CFD) for a wide range of relative flow rates. The new formulation was achieved through comparison of experimental and numerical results obtained for a low-specific-speed (nondimensional specific speed ≈ 0.7) helico-axial compression cell in series. CFD results revealed secondary flows and strong rotor–stator interactions. Steady-state simulations with the standard SST turbulence model were unable to accurately predict pump performance because of such inherently unsteady features. Unsteady simulations improved the predicted performance, but the head coefficient was up to 10% higher than test results at part-load operation. Through calibration of a rotation–curvature correction, the error in the predicted head coefficient was essentially eliminated for relative flow rates above 50% relative flow. Below 47% relative flow, a rotating stall-phenomenon was identified. The stall cell propagated at a rate of 0.4 times the impeller angular frequency, and we identified a propagation mechanism related to a circumferential variation in impeller tip leakage flow (TLF) rate. The presented turbulence model formulation can improve performance predictions in turbomachinery applications where leakage flows are significant, and forms a basis for future work on extended modeling of increasingly complex operating conditions.
Effects of Training Volume in the Bench-Press Exercise Performed With Interrepetition Rest Periods on Strength Gains and Neuromuscular Adaptations
Authors: Páez-Maldonado José A. , Cano Claro , Cornejo-Daza Pedro J. , Sánchez-Valdepeñas Juan , Rodiles-Guerrero Luis , Wernbom Mathias , Ortega-Becerra Manuel , Pareja-Blanco Fernando
Published: October 2024

Purpose: To investigate the effects of 3 training volumes in the bench-press exercise performed with interrepetition rest periods, matched for fatigue, on strength gains and neuromuscular adaptations. Methods: Forty-three resistance-trained men were randomized into 3 groups: low (LOW), moderate (MOD), and high (HIG) volume. The intensities increased from 70% to 85% of 1-repetition maximum (1RM) over the 8-week training period. Each session consisted of only 1 set with short interrepetition rest periods. LOW performed only 3 repetitions per session (8-wk total: 48 repetitions); MOD completed 15, 12, 10, and 8 repetitions per session with 70%, 75%, 80%, and 85% 1RM, respectively (8-wk total: 180); and HIG performed 24, 21, 18, and 15 repetitions per session with 70%, 75%, 80%, and 85% 1RM, respectively (8-wk total: 312). Progressive loading and fatigue tests were conducted in the bench-press exercise before and after the training period. Electromyography (EMG) signals from the triceps brachii were registered during these tests. Results: HIG and MOD showed higher velocity loss than LOW (16% vs 12%). No significant group × time interaction was observed for any variable. All groups improved significantly in all strength-related variables, except for maximal unloaded velocity, where only MOD obtained significant gains. Only LOW and MOD induced significant improvements in EMG. MOD obtained the greatest effect sizes in almost all strength variables. Conclusions: No significant differences were found in the performance gains obtained by each group despite the wide differences in the total volume accumulated by each group.
Normative Extensor Hallucis Brevis Muscle Activity During Locomotion Following the Development of a Novel Ultrasound-Guided Fine-Wire Electromyography Protocol
Authors: Robb Kelly A. , Sutherland Keara , Perry Stephen D.
Published: October 2024

Fine-wire electromyography (EMG) is a traditional laboratory technique to estimate muscle activity of the small foot muscles, however, recordings have not been reported from extensor hallucis brevis (EHB). As an extensor of the great toe, EHB is an important muscle when studying physiological changes associated with foot pathologies such as hallux valgus. The purpose of this study was to develop an ultrasound-guided fine-wire EMG protocol to record EHB muscle activity and report normative EMG profiles of healthy young adults during locomotion. Sixteen asymptomatic young adults completed 20 walking trials at a self-selected velocity. Ensemble averages were calculated from the time normalized linear envelopes and represented from 0% to 100% of the single stance phase of gait. EHB muscle bursts were observed between 0% and 20% of the stance phase of gait in all participants. A second burst of EMG was observed between 80% and 100% of stance in 50% of the participants. This study introduces a novel ultrasound-guided EMG protocol and normative data from EHB recordings suggest a synergistic role to anterior compartment musculature at contact. These results provide preliminary insights into understanding the functional role of EHB and may help elucidate the biomechanical factors exacerbating the progression of hallux pathologies.
Results From the First Para Report Card on Physical Activity for Children and Adolescents With Disabilities in Chile
Authors: Aguilar-Farias Nicolas , Miranda-Marquez Sebastian , Toledo-Vargas Marcelo , Sadarangani Kabir P. , Ibarra-Mora Jessica , Martino-Fuentealba Pia , Rodriguez-Rodriguez Fernando , Cristi-Montero Carlos , Henríquez Matías , Cortinez-O’Ryan Andrea
Published: October 2024

Background: Global initiatives have been put in place to attain a thorough understanding of worldwide variations in physical activity (PA) among children and adolescents. Yet, there is limited knowledge about PA-related indicators, specifically for children and adolescents with disabilities (CAWD). To bridge this data gap, the Global Matrix of Para Report Cards (PRCs) of CAWD initiative was established to address the scarcity of information on PA for this population globally. The purpose of this manuscript is to summarize the results of Chile’s First PRC on PA for CAWD. Methods: Chile’s PRC included 10 core PA indicators common to the Global Matrix of PRCs. Evidence from scientific articles, reports, and databases available or released from 2018 to January 2022 was included for each indicator. A scientific committee collected and analyzed the data, assigning letter grades (A–F) based on benchmarks. Results: The grades assigned were as follows: Overall PA, D−; Organized Sports and Physical Activity Participation, C−; Active Play, INCOMPLETE; Active Transportation, D−; Sedentary Behavior, F; Physical Fitness, INCOMPLETE; Family and Peers, D+; School, C+; Community and Environment, D+; Government, B−. Conclusions: Chile scored low in most indicators. Although some efforts have been made in the last decade in terms of policies, these have not been reflected in PA and related behaviors in CAWD. The results underscore that maintaining the current situation is inadequate for addressing the widespread problem of physical inactivity among CAWD in Chile, emphasizing the urgency for substantial changes and a comprehensive approach to effectively combat this crisis.
Social Comparison, Social Indispensability, or Both? On the Psychological Mechanisms Underlying Effort Gains in Swimming Relays
Authors: Torka Ann-Kathrin , Hüffmeier Joachim , Fischer Sebastian , Braun Claudia
Published: October 2024

Members of swimming relays often show effort gains in relays (i.e., more effort and faster swimming times in the relay vs. the individual competition). The weakest relay members typically exhibit the most pronounced effort gains. However, the underlying psychological processes are unclear. Prior research suggests social comparisons with stronger fellow relay members, perceived social indispensability, or a combination of both processes as plausible mediators. In Study 1, using linear mixed model and regression analyses on N = 239 observations from 222 elite U.S. college swimmers, we found empirical support only for the social indispensability hypothesis. Study 2, a survey among N = 46 German national team swimmers, substantiated the results, because the athletes most often mentioned processes related to social indispensability as motivating them. Our findings offer theoretical conclusions for expectancy × value models on team member effort expenditure and practical implications for coaching and selecting the weakest members for swimming relays.
Asymptomatic bacteriuria screening for developing countries using a modified water quality test kit
Authors: Stocki Jolie A. , Fleck Rachel C. , Nguyen Ivy B. , Walde Ryan , Mobley Harry L. T. , Shea Allyson E.
Published: October 2024

Between 2% and 15% of pregnant women unknowingly experience asymptomatic bacteriuria (ASB), defined as ≥10
5
CFU per milliliter of urine in the absence of symptoms. ASB increases the risk of adverse pregnancy outcomes including pyelonephritis, preterm labor, and low-birth weight infants. While pregnant women in the United States are routinely screened for ASB, those in developing countries with limited resources and funding lack an accurate mechanism for ASB screening. Aquagenx water quality test kits detect
Escherichia coli
, the most common causative agent of ASB, and total coliform bacteria in drinking water via colorimetric and fluorescent indicators. We found that the Aquagenx system is compatible with human urine and then proceeded to develop an ASB screening protocol using disposable inoculating loops. Our protocol diagnosed artificial ASB
−
samples (10
4
CFU/mL
E. coli
) with a false positive (FP) rate of 33% (
n
= 18) and ASB
+
(10
5
CFU/mL
E. coli
) with a false negative (FN) rate of 5.6% (
n
= 18). Clinical sample testing with our protocol revealed a FP rate of 0% in ASB
−
samples (
n
= 28) and a FN rate of 0% in ASB
+
samples caused by coliforms (
n
= 13). Aquagenx did not detect ASB in nine clinical samples with non-coliform etiological agents due to the limitations of the technology. However, with very high accuracy for detection of
E. coli
and other causative agents that collectively account for 90.1% of ASB cases, these kits could be used as a diagnostic ASB screening tool in developing countries in which there is currently no alternative to urine culture.

IMPORTANCE

Asymptomatic bacteriuria (ASB) affects 2%–15% of pregnant women and can result in adverse maternal and fetal outcomes if left undetected and untreated. In the United States and other developed nations, pregnant women are regularly screened for ASB via urine culture. However, in low-resource countries where bacterial culture is not available, dipstick testing is used. Although accurate in cases of symptomatic bacteriuria, dipstick detection is ineffective for detecting ASB. Here, we made use of an existing water quality field test for ASB urine screening, which would be readily deployable in low-resource settings. We optimized a dilution protocol for sampling patient urine within the detection limits of the Aquagenx kit technology. Overall, we were able to detect ASB samples with Gram-negative pathogens that collectively account for 90% of all ASB cases. Utilization of this repurposed technology for proactive medical screening may help prevent adverse pregnancy and birth outcomes due to ASB.
A framework for training graduate students and campus communities in inclusive teaching
Authors: Batterton Berit E. , Neill C. Melman , Biggs Christopher R. , Rempel Hannah S.
Published: October 2024

While graduate student teaching assistants (TAs) contribute significantly to university education, many graduate programs across diverse disciplines offer limited formal pedagogical training. In turn, many researchers informally develop teaching and mentoring skills as they advance to faculty positions or related careers. This can perpetuate a lag in the implementation of inclusive educational environments despite the clear benefits demonstrated by recent pedagogical research. For instance, the integration of inclusive teaching strategies like universal design for learning, growth mindset feedback, and the use of relatable role models in curricula may help increase the persistence, success, and self-efficacy of traditionally underrepresented groups in the sciences. Additionally, research indicates that training graduate TAs in evidence-based practices may have benefits beyond teaching efficacy, such as greater confidence in research preparedness and science communication—skills applicable to any scientific field or career path. Here, we developed and implemented an inclusive teaching series for a marine science department that included: (i) campus-wide pedagogical journal article discussions and knowledge-sharing, (ii) expert-led interactive workshops on evidence-based teaching strategies, and (iii) a graduate TA professional development module on inclusive lesson planning with opportunities to teach and receive feedback. Based on our experiences, we share a framework and resources to facilitate a broader adoption of formalized TA training in inclusive teaching practices within graduate programs across a variety of fields.
Olfactory and trigeminal routes of HSV-1 CNS infection with regional microglial heterogeneity
Authors: Niemeyer Christy S. , Merle Laetitia , Bubak Andrew N. , Baxter B. Dnate’ , Gentile Polese Arianna , Colon-Reyes Katherine , Vang Sandy , Hassell James E. , Bruce Kimberley D. , Nagel Maria A. , Restrepo Diego
Published: October 2024

Herpes simplex virus type 1 (HSV-1) primarily targets the oral and nasal epithelia before establishing latency in the trigeminal ganglion (TG) and other peripheral ganglia. HSV-1 can also infect and become latent in the central nervous system (CNS) independent of latency in the TGs. Recent studies suggest entry to the CNS via two distinct routes: the TG-brainstem connection and olfactory nerve; however, to date, there is no characterization of brain regions targeted during HSV-1 primary infection. Furthermore, the immune response by microglia may also contribute to the heterogeneity between different brain regions. However, the response to HSV-1 by microglia has not been characterized in a region-specific manner. This study investigated the time course of HSV-1 spread within the olfactory epithelium (OE) and CNS following intranasal inoculation and the corresponding macrophage/microglial response in a C57BL/6 mouse model. We found an apical to basal spread of HSV-1 within the OE and underlying tissue accompanied by an inflammatory response of macrophages. OE infection was followed by infection of a small subset of brain regions targeted by the TG in the brainstem and other cranial nerve nuclei, including the vagus and hypoglossal nerve. Furthermore, other brain regions were positive for HSV-1 antigens, such as the locus coeruleus (LC), raphe nucleus (RaN), and hypothalamus while sparing the hippocampus and cortex. Within each brain region, microglia activation also varied widely. These findings provide critical insights into the region-specific dissemination of HSV-1 within the CNS, elucidating potential mechanisms linking viral infection to neurological and neurodegenerative diseases.

IMPORTANCE

This study shows how herpes simplex virus type 1 (HSV-1) spreads within the brain after infecting the nasal passages. Our data reveal the distinct pattern of HSV-1 through the brain during a non-encephalitic infection. Furthermore, microglial activation was also temporally and spatially specific, with some regions of the brain having sustained microglial activation even in the absence of viral antigens. Previous reports have identified specific brain regions found to be positive for HSV-1 infection; however, to date, there has not been a concise investigation of the anatomical spread of HSV-1 and the brain regions consistently vulnerable to viral entry and spread. Understanding these region-specific differences in infection and immune response is crucial because it links HSV-1 infection to potential triggers for neurological and neurodegenerative diseases.
Torque-speed relationship of the flagellar motor with dual-stator systems in
Pseudomonas aeruginosa
Authors: Wu Haolin , Wu Zhengyu , Tian Maojin , Zhang Rongjing , Yuan Junhua
Published: October 2024

The single polar flagellar motor in
Pseudomonas aeruginosa
is equipped with two stator systems, MotAB and MotCD, both driven by H
+
ions. The torque-speed relationship for flagellar motors with two stator systems has not been explored previously. In this study, we developed a method that utilizes optical trapping and fluorescence labeling to measure the torque-speed relationships for the wild-type
P. aeruginosa
motor with dual stators and mutant strains with a single stator system, revealing surprising differences in them. Moreover, we found that the MotAB stators exhibit slip-bond behavior in load dependence, contrasting with the catch-bond behavior of the MotCD stators and
Escherichia coli
stators. Further examination of the solvent isotope and pH effects on the torque-speed relationships of these stator systems provided additional insights into their dynamics. Interestingly, we discovered that the torque of the wild-type motor is similar to the combined torque of motors with MotAB or MotCD stators, indicating an additive contribution from the two stator types in the wild-type motors. These findings underscore the enhanced adaptability of
P. aeruginosa
to a wide range of external environments with varying load conditions.

IMPORTANCE

We developed a novel method to measure the flagellar motor torque-speed relationship by trapping a swimming bacterium using optical tweezers. Using the
P. aeruginosa
flagellar motor as a model system to investigate motor dynamics with dual stator types, we measured the torque-speed relationships for wild-type motors with dual stator types and mutants with a single type. We found drastic differences that stem from the varying load dependencies of stator stability. These variations enable bacteria to rapidly adjust their stator composition in response to external load conditions. Interestingly, we observed that the torque of the wild-type motor is akin to the cumulative torque of motors with either stator type, indicating an additive contribution from the two stator types in wild-type motors. The methodology we established here can be readily employed to study motor dynamics in other flagellated bacteria.
The vitamin D receptor is essential for the replication of pseudorabies virus
Authors: Zeng Lei , Wang Shu-Yi , Du Meng-Hua , Chu Bei-Bei , Ming Sheng-Li
Published: October 2024

The vitamin D receptor (VDR) is a nuclear steroid receptor that regulates the expression of genes across various biological functions. However, the role of VDR in pseudorabies virus (PRV) infection has not yet been explored. We discovered that VDR positively influenced PRV proliferation because knockdown of VDR impaired PRV proliferation, whereas its overexpression promoted it. Additionally, we observed that PRV infection upregulated VDR transcription alongside 1,25-dihydroxyvitamin D3 (VD
3
) synthesis, contingent on p53 activation. Furthermore, VDR knockdown hindered PRV-induced lipid synthesis, implicating VDR’s involvement in this process. To decipher the mechanism behind VDR’s stimulation of lipid synthesis during PRV infection, we conducted RNA sequencing (RNA-seq) and found significant enrichment of genes in the Ca
2+
signaling pathway. Measurements of Ca
2+
indicated that VDR facilitated Ca
2+
absorption. Moreover, the PI3K/AKT/mTORC1 and AMPK/mTORC1 pathways were also enriched in our RNA-seq data. Interfering with VDR expression, or chelating Ca
2+
using BAPTA-AM, markedly impacted the activation of PI3K/AKT/mTORC1 and AMPK/mTORC1 pathways, lipid synthesis, and PRV proliferation. In summary, our study demonstrates that PRV infection promotes VDR expression, thereby enhancing Ca
2+
absorption and activating PI3K/AKT/mTORC1- and AMPK/mTORC1-mediated lipid synthesis. Our findings offer new insights into strategies for PRV prevention.

IMPORTANCE

Vitamin D, beyond its well-known benefits for bone health and immune function, also plays a pivotal role in regulating gene expression through its receptor, the vitamin D receptor (VDR). Although VDR’s influence spans multiple biological processes, its relationship with viral infections, particularly pseudorabies virus (PRV), remains underexplored. Our research illustrates a complex interplay where PRV infection boosts VDR expression, which in turn enhances Ca
2+
absorption, leading to the activation of critical lipid synthesis pathways, PI3K/AKT/mTORC1 and AMPK/mTORC1. These findings not only deepen our understanding of the intricate dynamics between host molecular mechanisms and viral proliferation but also open avenues for exploring new strategies aimed at preventing PRV infection. By targeting components of the VDR-related signaling pathways, we can potentially develop novel therapeutic interventions against PRV and possibly other similar viral infections.
Metabolic interplay between
Proteus mirabilis
and
Enterococcus faecalis
facilitates polymicrobial biofilm formation and invasive disease
Authors: Hunt Benjamin C. , Brix Vitus , Vath Joseph , Guterman Lauren Beryl , Taddei Steven M. , Deka Namrata , Learman Brian S. , Brauer Aimee L. , Shen Shichen , Qu Jun , Armbruster Chelsie E.
Published: October 2024

Biofilms play an important role in the development and pathogenesis of catheter-associated urinary tract infection (CAUTI).
Proteus mirabilis
and
Enterococcus faecalis
are common CAUTI pathogens that persistently co-colonize the catheterized urinary tract and form biofilms with increased biomass and antibiotic resistance. In this study, we uncover the metabolic interplay that drives biofilm enhancement and examine the contribution to CAUTI severity. Through compositional and proteomic biofilm analyses, we determined that the increase in biofilm biomass stems from an increase in the protein fraction of the polymicrobial biofilm. We further observed an enrichment in proteins associated with ornithine and arginine metabolism in polymicrobial biofilms compared with single-species biofilms. We show that arginine/ornithine antiport by
E. faecalis
promotes arginine biosynthesis and metabolism in
P. mirabilis
, ultimately driving the increase in polymicrobial biofilm protein content without affecting viability of either species. We further show that disrupting
E. faecalis
ornithine antiport alters the metabolic profile of polymicrobial biofilms and prevents enhancement, and this defect was complemented by supplementation with exogenous ornithine. In a murine model of CAUTI, ornithine antiport did not contribute to
E. faecalis
colonization but was required for the increased incidence of urinary stone formation and bacteremia that occurs during polymicrobial CAUTI with
P. mirabilis
. Thus, disrupting metabolic interplay between common co-colonizing species may represent a viable strategy for reducing risk of bacteremia.

IMPORTANCE

Chronic infections often involve the formation of antibiotic-resistant biofilm communities that include multiple different microbes, which pose a challenge for effective treatment. In the catheterized urinary tract, potential pathogens persistently co-colonize for long periods of time and the interactions between them can lead to more severe disease outcomes. In this study, we identified the metabolite L-ornithine as a key mediator of disease-enhancing interactions between two common and challenging pathogens,
Enterococcus faecalis
and
Proteus mirabilis
. Disrupting ornithine-mediated interactions may therefore represent a strategy to prevent polymicrobial biofilm formation and decrease risk of severe disease.
Epidermal growth factor receptor signaling governs the host inflammatory response to invasive aspergillosis
Authors: Liu Hong , Lin Jianfeng , Phan Quynh T. , Bruno Vincent M. , Filler Scott G.
Published: October 2024

The epidermal growth factor receptor (EGFR) has been identified as an epithelial cell receptor for Mucorales fungi and
Candida albicans
. Blocking EGFR with small molecule inhibitors reduces disease severity in mouse models of mucormycosis and oropharyngeal candidiasis. In contrast, cases of invasive aspergillosis have been reported in cancer patients who were treated with EGFR inhibitors, suggesting that EGFR signaling may play a protective role in the host defense against this infection. Here, we analyzed transcriptomic data from the lungs of mice with invasive aspergillosis and found evidence that
Aspergillus fumigatus
infection activates multiple genes that are predicted to function in the EGFR signaling pathway. We also found that
A. fumigatus
infection activates EGFR in both a human small-airway epithelial (HSAE) cell line and in the lungs of immunosuppressed mice. EGFR signaling in HSAE cells is required for maximal endocytosis of
A. fumigatus
and for fungal-induced proinflammatory cytokine and chemokine production. In a corticosteroid immunosuppressed mouse model of invasive pulmonary aspergillosis, inhibition of EGFR with gefitinib decreased whole-lung cytokine and chemokine levels and reduced accumulation of phagocytes in the lung, leading to a decrease in fungal killing, an increase in pulmonary fungal burden, and accelerated mortality. Thus, EGFR signaling is required for pulmonary epithelial cells to orchestrate the host innate immune defense against invasive aspergillosis in immunosuppressed hosts.

IMPORTANCE

When
A. fumigatus
infects the lungs, it invades epithelial cells that line the airways. During this process, the fungus interacts with epithelial cell receptors. This interaction stimulates epithelial cells to endocytose the fungus. It also induces these cells to secrete proinflammatory cytokines and chemokines that recruit phagocytes to the site of infection where they can kill the fungus. Here, we show that in small-airway epithelial cells, the EGFR acts as a sensor for
A. fumigatus
that triggers the production of chemokines in response to fungal infection. In corticosteroid-immunosuppressed mice, blocking EGFR with the kinase inhibitor gefitinib reduces chemokine production in the lungs. This leads to decreased accumulation of neutrophils and dendritic cells in the lungs, reduced
A. fumigatus
killing, and increased mortality. These results provide a potential explanation as to why some cancer patients who are treated with EGFR inhibitors develop invasive aspergillosis.
PlsX and PlsY: Additional roles beyond glycerophospholipid synthesis in Gram-negative bacteria
Authors: Rex Audrey N. , Simpson Brent W. , Bokinsky Gregory , Trent M. Stephen
Published: October 2024

The unique asymmetry of the Gram-negative outer membrane, with glycerophospholipids (GPLs) in the inner leaflet and lipopolysaccharide (LPS) in the outer leaflet, works to resist external stressors and prevent the entry of toxic compounds. Thus, GPL and LPS synthesis must be tightly controlled to maintain the integrity of this essential structure. We sought to decipher why organisms like
Escherichia coli
possess two redundant pathways—PlsB and PlsX/Y—for synthesis of the GPL precursor lysophosphatidic acid (LPA). LPA is then converted by PlsC to the universal precursor for GPL synthesis, phosphatidic acid (PA). PlsB and PlsC are essential in
E. coli
, indicating they serve as the major pathway for PA synthesis. While loss of PlsX or PlsY individually has little consequence on the cell, the absence of both was lethal. To understand the synthetic lethality of this seemingly redundant PlsX/Y pathway, we performed a suppressor screen. Suppressor analysis indicated that ∆
plsXY
requires increased levels of glycerol-3-phosphate (G3P), a GPL precursor. In agreement, ∆
plsXY
required supplementation with G3P for survival. Furthermore, loss of PlsX dysregulated fatty acid synthesis, resulting in increased long-chain fatty acids. We show that although PlsX/Y together contribute to PA synthesis, they also contribute to the regulation of overall membrane biogenesis. Thus, synthetic lethality of ∆
plsXY
is multifactorial, suggesting that PlsX/Y has been maintained as a redundant system to fine-tune the synthesis of major lipids and promote cell envelope homeostasis.

IMPORTANCE

Gram-negative bacteria must maintain optimal ratios of glycerophospholipids and lipopolysaccharide within the cell envelope for viability. Maintenance of proper outer membrane asymmetry allows for resistance to toxins and antibiotics. Here, we describe additional roles of PlsX and PlsY in
Escherichia coli
beyond lysophosphatidic acid synthesis, a key precursor of all glycerophospholipids. These findings suggest that PlsX and PlsY also play a larger role in impacting homeostasis of lipid synthesis.
Trehalose polyphleates participate in
Mycobacterium abscessus
fitness and pathogenesis
Authors: Malmsheimer Silke , Daher Wassim , Tasrini Yara , Hamela Claire , Aguilera-Correa John Jairo , Chalut Christian , Hatfull Graham F. , Kremer Laurent
Published: October 2024

Mycobacteria produce a large repertoire of surface-exposed lipids with major biological functions. Among these lipids, trehalose polyphleates (TPPs) are instrumental in the infection of
Mycobacterium abscessus
by the therapeutic phage BPs. However, while the biosynthesis and transport of TPPs across the membrane by MmpL10 have been reported, the role of TPPs in host infection remains enigmatic. Here, we addressed whether the loss of TPPs influences interactions with macrophages and the virulence of
M. abscessus
. As anticipated, the deletion of
mmpL10
in smooth (S) and rough (R) variants of
M. abscessus
abrogated TPP production, which was rescued upon gene complementation. Importantly, infection of human THP-1 cells with the
mmpL10
mutants was associated with decreased intramacrophage survival and a reduced proportion of infected cells. The rough
mmpL10
mutant showed an impaired capacity to block phagosomal acidification and was unable to co-localize with Galectin-3, a marker of phagosomal membrane damage. This suggests that TPPs participate, directly or indirectly, in phagolysosomal fusion and in phagosomal membrane damage to establish cytosolic communication. The TPP defect that affects the fitness and virulence of
M. abscessus
was further demonstrated in zebrafish embryos using a rough clinical strain resistant to phage BPs and harboring a frameshift mutation in
mmpL10
. Infection with this strain was correlated with a slight decrease in embryo survival and a reduced bacterial burden as compared to the corresponding parental and complemented derivatives. Together, these results indicate that TPPs are important surface lipids contributing to the pathogenicity of
M. abscessus
.

IMPORTANCE

Trehalose polyphleates (TPPs) are complex lipids associated with the mycobacterial cell surface and were identified 50 years ago. While the TPP biosynthetic pathway has been described recently, the role of these lipids in the biology of mycobacteria remains yet to be established. The wide distribution of TPPs across mycobacterial species suggests that they may exhibit important functions in these actinobacteria. Here, we demonstrate that
Mycobacterium abscessus,
an emerging multidrug-resistant pathogen that causes severe lung diseases in cystic fibrosis patients, requires TPPs for survival in macrophages and virulence in a zebrafish model of infection. These findings support the importance of this underexplored family of lipids in mycobacterial pathogenesis.
Maternal consumption of yoghurt activating the aryl hydrocarbon receptor increases group 3 innate lymphoid cells in murine offspring
Authors: Pimentel Grégory , Roder Thomas , Bär Cornelia , Christensen Sandro , Sattari Zahra , Kalbermatter Cristina , von Ah Ueli , Robert Christelle A. M. , Mateo Pierre , Bruggmann Rémy , Ganal-Vonarburg Stephanie C. , Vergères Guy
Published: October 2024

Indole derivatives are microbial metabolites of the tryptophan pathway involved in gut immune homeostasis. They bind to the aryl hydrocarbon receptor (AhR), thereby modulating development of intestinal group 3 innate lymphoid cells (ILC3) and subsequent interleukin-22 production. In mice, indole derivatives of the maternal microbiota can reach the milk and drive early postnatal ILC3 development. Apart from the gut microbiota, lactic acid bacteria (LAB) also produce indole compounds during milk fermentation. Using germ-free mice, the aim of our study was to test if maternal intake of a dairy product enriched in AhR-activating indoles produced by fermentation could boost maturation of the intestinal innate immune system in the offspring. A set of 631 LAB strains were genetically screened for their potential to produce indole compounds. Among these, 125 strains were tested in combination with standard strains to produce yoghurts that were screened for their ability to activate AhR
in vitro
using the HepG2–AhR–Luc cell line. The most active yoghurt and a control yoghurt were formulated as pellets and fed to germ-free dams during pregnancy and lactation. Analysis of the offspring on postnatal day 14 using flow cytometry revealed an increase in the frequency of small intestinal lamina propria NKp46 +ILC3 s in the pups born to dams that had consumed the purified diet containing an AhR-active yoghurt (AhrY-diet) compared to control yoghurt (ConY-diet). Selection of LABs based on their ability to produce a fermented dairy able to activate AhR appears to be an effective approach to produce a yoghurt with immunomodulatory properties.

IMPORTANCE

Key progresses in the sequencing and functional annotation of microbial organisms have revolutionized research in the fields of human metabolism and food biotechnology. In particular, the gut microbiome is now recognized as an important mediator of the impact of nutrition on human metabolism. Annotated genomes of a large number of bacteria are now available worldwide, which selectively transform food through fermentation to produce specific bioactive compounds with the potential to modulate human health. A previous research has demonstrated that the maternal microbiota shapes the neonatal immune system. Similarly, this report shows that lactic acid bacteria can be selected to produce fermented food that can also modulate postnatal intestinal immunity.
Transcriptional response of
Methanosarcina acetivorans
to repression of the energy-conserving methanophenazine: CoM-CoB heterodisulfide reductase enzyme HdrED
Authors: Buan Nicole R. , Metcalf William W.
Published: October 2024

Methane-producing archaea are key organisms in the anaerobic carbon cycle. These organisms, also called methanogens, grow by converting substrate to methane gas in a process called methanogenesis. Previous research showed that the reduction of the terminal electron acceptor is the rate-limiting step in methanogenesis by
Methanosarcina acetivorans
. In order to gain insight into how the cells sense and respond to the availability of the terminal electron acceptor, we designed an experiment to deplete cells of the essential terminal oxidase enzyme, HdrED. We found that the depletion of HdrED
in vivo
results in a higher abundance of transcripts for methyltransferases (
mtaC2, mtaB3, mtaC3
), coenzyme B biosynthesis, C1 metabolism, and pyrimidine compounds. In most cases, these changes were distinct from transcript abundance changes observed during the transition from exponential growth to stationary phase cultures. These data implicate the methylotrophic methanogenesis regulator MsrC (MA4383) in CoM-S-S-CoB heterodisulfide sensing and indicate cells have a specific mechanism to sense intracellular ratio of CoM-S-S-CoB, coenzyme M, and coenzyme B thiols and further suggest transcripts encoding translation and methanogenesis functions are controlled by feed-forward regulation depending on substrate availability.

IMPORTANCE

Methanosarcina
is an emerging model archaeon and synthetic biology platform for the production of renewable energy and sustainable chemicals to reduce dependence on petroleum. Research into metabolic networks and gene regulation in this organism and other methanogens will inform genome-scale metabolic modeling and microbial function prediction in uncultured or non-model anaerobes and archaea. This study suggests methanogens use unknown mechanisms to efficiently couple methanogenesis to gene regulation via CoM-S-S-CoB and ATP availability.
Highlight signatures of vaginal microbiota and metabolome contributed to the occurrence and recurrence of vulvovaginal candidiasis
Authors: Liang Yiheng , Huang Zhuoqi , Fan Shangrong , Li Changzhong , Huang Liting , Huang Chunhua , Hutchins Andrew P. , Fang Chao , Zhang Xiaowei
Published: October 2024

Vulvovaginal candidiasis (VVC) is a common vaginal infectious disease caused by
Candida
. The high recurrence rate of VVC is a great clinical challenge, with recurrent VVC (RVVC) defined as four or more episodes within a year. In this study, we recruited 31 RVVC patients, 28 VVC patients, and 29 healthy women. Vaginal samples were collected for metagenomic and metabolic analysis. RVVC and VVC groups presented similar clinical symptoms, with only a significantly increased incidence of swelling in the VVC group. Vaginal microbiota in VVC/RVVC exhibited a decreased abundance of
Lactobacillus
and increased bacterial vaginosis-associated bacteria, such as
Gardnerella
,
Prevotella
, and
Atopobium
. Notably,
Lactobacillus iners
was higher in RVVC, suggesting not all
Lactobacillus
species are protective. Healthy women showed lower overall microbiota diversity, emphasizing single-species dominance for stability. Glycogen metabolism pathways were enriched in RVVC/VVC, and were correlated with
Atopobium vaginae
,
Prevotella bivia
, and
Lactobacillus jensenii
. Peptidoglycan synthesis pathways, associated with
P. bivia
, were enriched, with the substrate L-glutamate elevated in RVVC, possibly promoted by
L. iners
. These findings shed light on potential therapeutic targets for recurrent VVC, contributing to the understanding of the intricate interplay between the metabolism of vaginal microbiome and disease.

IMPORTANCE

This study enhances our knowledge of the vaginal microbiota dynamics and the role of associated metabolites in individuals with vulvovaginal candidiasis (VVC) and recurrent vulvovaginal candidiasis through shotgun sequencing and multi-omics analysis. The relationship between metabolites and vaginal microbiota and disease state was revealed. The accumulation of L-glutamate generated in glycogen metabolism, which is governed by
Lactobacillus iners
or bacterial vaginosis-associated bacteria, may contribute to the incidence and recurrence of VVC. Such insights have the potential to impact the treatment and prevention strategies for these common yet distressing conditions, potentially leading to targeted therapies and improved patient outcomes.
Cariogenic potential of the
Streptococcus mutans
Cid/Lrg system: an
in vivo
animal case study
Authors: Ahn Sang-Joon , Rice Kelly C. , Culp David J.
Published: October 2024

In our prior study using a dual-species (
Streptococcus mutans/Streptococcus gordonii
) competitive mouse caries model to investigate the contribution of
S. mutans
LrgAB to
in vivo
fitness,
S. mutans
wild-type and Δ
lrgAB
mutants consistently outnumbered
S. gordonii
and had high caries scores, even though the Δ
lrgAB
mutant is highly sensitive to oxidative stress. To determine whether the highly cariogenic sucrose diet used in the previous study masked the contribution of LrgAB to competitive fitness of
S. mutans
against
S. gordonii
, we recapitulated our previous mouse caries experiment with a modification in which 4% sucrose drinking water was replaced with sterile water, hypothesized to decrease the frequency of exposure of mice to sucrose, a determinant in the cariogenicity of
S. mutans
. Given that both
S. mutans
Δ
lrgAB
and Δ
cidB
mutants are sensitive to oxidative stress and share similar transcriptional profiles, these strains, as well as wild-type UA159, were tested in this modified dual-species mouse caries model. When comparing between groups the colonization within molar dental biofilms of
S. mutans
strains, Δ
lrgAB
mutant was at a level similar to the wild type, whereas
S. mutans
Δ
cidB
was modestly lower than both wild-type and
S. mutans
Δ
lrgAB
. The severity of total sulcal caries in both the
∆cidB
and
∆lrgAB
mutant infections was significantly lower than that of wild type. These results demonstrate that the Cid/Lrg system aids in
S. mutans
fitness against
S. gordonii
and caries potential
in vivo
, a phenotype likely masked in our previous study by more frequent exposure to sucrose.

IMPORTANCE

The development of a mature biofilm on the tooth surface is the central event in the pathogenesis of dental caries, which primarily requires that cariogenic organisms withstand the limited resources or environmental fluctuations experienced in the oral cavity. The sensitive and heterogeneous response of the
cid
and
lrg
operons to complex external signals has been hypothesized to trigger differentiation of the
Streptococcus mutans
biofilm community into distinct functional subpopulations to promote survival and persistence of the
S. mutans
community when challenged by an unfavorable environment. The study described herein enlightens our understanding of how Cid/Lrg contributes to
S. mutans
pathogenic potential
in vivo
(caries development), warranting further research regarding the adaptive role of Cid/Lrg system in human oral biofilms toward the development of anti-caries strategies directed at the Cid/Lrg system.