The bacterial gut microbiota of wood- and humus-feeding termites: Diazotrophic populations and compartment-specific response of bacterial communities to environmental factors

The subject of this thesis is the influence of the microenvironment on the symbiosis between higher termites and their intestinal bacteria. The gut environmental factors pH, hydrogen partial pressure, redox potential and nitrogen pool size were measured. Bacterial gut community structure from each highly compartmentalized gut section was investigated. Furthermore, one specific function, nitrogen fixation, was comparatively analyzed in lower termites, higher termites and cockroaches. Hydrogen partial pressure, pH and redox potential in the gut compartments of humus- and soil-feeding termites were measured using microsensors. The size of the entire bacterial communities in each compartment was determined by 16S rRNA gene copies in qPCR. The diets of humus- and soil-feeders are nitrogen-rich, so the pool size of ammonia, nitrite and nitrate were also quantified by colorimetric assay. Higher termites have adapted to utilize diverse lignocellulosic diets in various stages of humification, like wood, humus and soil. The high alkalinity in the anterior hindgut of humus- and soil-feeding termites may play an important role in the digestion of proteins and polypeptides. Our comprehensive determination of physicochemical parameters reinforce the hypothesis that intestinal microenvironments are evolutionarily adapted to diet-related differences. The analysis of bacterial diversity by amplicon sequencing (Miseq) of 16S rRNA genes underscored that the community structure of intestinal bacteria in each gut section is influenced by multiple environmental factors like pH, hydrogen and host dietary substrate. The gut bacteria in homologous compartments of hindguts of humus- and soil-feeders showed similarity even when the hosts were from different subfamilies. In wood- and grass- feeding termites, dominating gut microbiota were from Actinobacteria, Fibrobacteres and Spirochaetes. On the other hand, abundant genera were from Bacteroidetes, Spirochaetes and Firmicutes in humus- and litter-feeding termites. This suggests that they make essential contributions to the digestive processes. Nitrogen supply should also influences the composition of the microbiota in termite guts, especially in wood-feeding termites, where diazotrophy is of major importance. From the study of nitrogen metabolism in different gut sections, the high concentrations of ammonia, nitrite and nitrate were found in the gut of humus- and soil-feeding termites not in wood-feeding termites. This phenomenon associated with the intake of the termites. For the wood feeders, they rely on a nitrogen-limiting diet with a high carbon to nitrogen ratio. They need some strategies to overcome this difficulty. Nitrogen fixation of symbiotic gut bacteria helps them in nitrogen nutrition supply. Quantification of nitrogen fixing populations was carried at DNA level by qPCR, using the nifH gene as a molecular marker. After normalized by 16S rRNA gene copy numbers, the ratio of nifH to 16S rRNA gene copy numbers was less than 0.15 in all termite species studied. Nevertheless, this surprisingly low proportion of diazotrophs is sufficient to account for the nitrogen fixation rate of the termites. It is supported by the nitrogen fixation ability measured by acetylene reduction assay of Treponema isolates from Zootermopsis angusticollis and live Zootermopsis sp. The bacterial symbionts of flagellate protists contribute to the nitrogen fixation in lower termites. Especially in Kalotermitidae, the abundant nifH genes which clustered with nifH genes from flagellate symbionts are consistent with the cospeciation of flagellates and lower termites. Nitrogen fixed by the endosymbiont can be converted to more valuable nitrogenous compounds such as amino acids and supplied directly for protein synthesis of the protist. This asset allows the protist to grow stably and independently, and ensures that the host termite maintains the essential cellulolytic protists. In wood-feeding higher termites, flagellates are lost and the diazotrophs in the gut link with fiber-associated bacteria. This was verified by comparative analysis of nifH genes in amplicon libraries and annotated metagenomes. Apart from flagellate symbionts, another interesting nifH subcluster is in Group IV. The verified diazotroph with only nif genes encoding Group IV nitrogenase revealed potential functional nifH subgroup in previously unfunctional Group IV. Endomicrobium cluster is abundant in Kalotermitidae, Termopsidae and Cryptoceridae. This is the first analysis of the diazotrophic communities in termite gut which take into account the potential diazotrophs with functional nifH in Group IV

Developmental iodine deficiency resulting in hypothyroidism reduces hippocampal ERK1/2 and CREB in lactational and adolescent rats

BACKGROUND: Developmental iodine deficiency (ID) leads to inadequate thyroid hormone that impairs learning and memory with an unclear mechanism. Here, we show that hippocampal extracellular signal-regulated kinase (ERK1/2) and cAMP response element-binding protein (CREB) are implicated in the impaired learning and memory in lactational and adolescent rat hippocampus following developmental ID and hypothyroidism. METHODS: Three developmental rat models were created by administrating dam rats with either iodine-deficient diet or propylthiouracil (PTU, 5 ppm or 15 ppm)-added drinking water from gestational day (GD) 6 till postnatal day (PN) 28. Then, the total and phorsporylated ERK1/2 and total and phorsporylated CREB in the hippocampus were detected with western blot on PN14, PN21, PN28 and PN42. RESULTS: The iodine-deficient and hypothyroid pups showed lower serum FT3 and FT4 levels, smaller body size, and delayed eyes opening. The mean number of surviving cells in the hippocampus of the iodine-deficient and 15 ppm PTU-treated rats was significantly reduced compared to controls (P < 0.05). Iodine-deficient and 15 ppm PTU-treatment groups demonstrated significantly lower level of total and phosphorylated ERK1/2 and CREB than the controls on PN14, PN21 and PN28 (P < 0.05, respectively). The reduction of ERK1/2 and CREB was not reversible with the restoration of serum thyroid hormone concentrations on PN42. CONCLUSIONS: Developmental ID and hypothyroidism down-regulate hippocampal ERK1/2 and CREB in lactational and adolescent rats

Developmental iodine deficiency and hypothyroidism impair neural development in rat hippocampus: involvement of doublecortin and NCAM-180

<p>Abstract</p> <p>Background</p> <p>Developmental iodine deficiency results in inadequate thyroid hormone (TH), which damages the hippocampus. Here, we explored the roles of hippocampal doublecortin and neural cell adhesion molecule (NCAM)-180 in developmental iodine deficiency and hypothyroidism.</p> <p>Methods</p> <p>Two developmental rat models were established with either an iodine-deficient diet, or propylthiouracil (PTU)-adulterated water (5 ppm or 15 ppm) to impair thyroid function, in pregnant rats from gestational day 6 until postnatal day (PN) 28. Silver-stained neurons and protein levels of doublecortin and NCAM-180 in several hippocampal subregions were assessed on PN14, PN21, PN28, and PN42.</p> <p>Results</p> <p>The results show that nerve fibers in iodine-deficient and 15 ppm PTU-treated rats were injured on PN28 and PN42. Downregulation of doublecortin and upregulation of NCAM-180 were observed in iodine-deficient and 15 ppm PTU-treated rats from PN14 on. These alterations were irreversible by the restoration of serum TH concentrations on PN42.</p> <p>Conclusion</p> <p>Developmental iodine deficiency and hypothyroidism impair the expression of doublecortin and NCAM-180, leading to nerve fiber malfunction and thus impairments in hippocampal development.</p

Identification of pyroptosis-related subtypes and establishment of prognostic model and immune characteristics in asthma

BackgroundAlthough studies have shown that cell pyroptosis is involved in the progression of asthma, a systematic analysis of the clinical significance of pyroptosis-related genes (PRGs) cooperating with immune cells in asthma patients is still lacking.MethodsTranscriptome sequencing datasets from patients with different disease courses were used to screen pyroptosis-related differentially expressed genes and perform biological function analysis. Clustering based on K-means unsupervised clustering method is performed to identify pyroptosis-related subtypes in asthma and explore biological functional characteristics of poorly controlled subtypes. Diagnostic markers between subtypes were screened and validated using an asthma mouse model. The infiltration of immune cells in airway epithelium was evaluated based on CIBERSORT, and the correlation between diagnostic markers and immune cells was analyzed. Finally, a risk prediction model was established and experimentally verified using differentially expressed genes between pyroptosis subtypes in combination with asthma control. The cMAP database and molecular docking were utilized to predict potential therapeutic drugs.ResultsNineteen differentially expressed PRGs and two subtypes were identified between patients with mild-to-moderate and severe asthma conditions. Significant differences were observed in asthma control and FEV1 reversibility between the two subtypes. Poor control subtypes were closely related to glucocorticoid resistance and airway remodeling. BNIP3 was identified as a diagnostic marker and associated with immune cell infiltration such as, M2 macrophages. The risk prediction model containing four genes has accurate classification efficiency and prediction value. Small molecules obtained from the cMAP database that may have therapeutic effects on asthma are mainly DPP4 inhibitors.ConclusionPyroptosis and its mediated immune phenotype are crucial in the occurrence, development, and prognosis of asthma. The predictive models and drugs developed on the basis of PRGs may provide new solutions for the management of asthma

Fine grid scale increases or decreases the trade-off effect between ES in mountain protected areas?

A crucial challenge in ecosystem management is the identification of trade-off effects among multiple ecosystem services (ESs), particularly in complex and ecologically vulnerable mountainous protected areas. Nevertheless, investigations into the spatio-temporal dynamics of trade-offs and synergies among ES within such protected regions remain limited. This study concentrated on the Qilian Mountain, a critical ecologically fragile protected area, utilized the Invest model to comprehensively analyze six ESs over the period 1985–2020. Employed Pearson correlation coefficient, we scrutinized trade-off and synergy relationships of these ES across varying grid scales (30 m, 1 km, and 10 km). Furthermore, GeoDetector, in tandem with multi-source data, is employed to unveil the potential drivers influencing the patterns of ES. Our findings revealed that: (1) Increasing data spatial resolution refines grid scales, yielding smoother spatial distributions of ES, and accentuates spatial disparities. (2) Synergistic relationships prevailed among protected area ES from 1985 to 2020, with correlations between carbon storage - water yield and habitat quality - water yield shifted from synergy to trade-off in 2015. (3) Distinct grid scales exert non-linear impacts on ES correlations, affecting both the magnitude and direction of these relationships. (4) Interactions among natural factors, climate, and landscape patterns are principal drivers of spatial heterogeneity in ES, with the contributions of dominant drivers exhibiting temporal variability. Remarkably, factors with stronger driving forces demonstrate greater temporal instability in their contribution rates. Our research underscores the necessity for comparative assessments of ES and their interrelations at diverse data spatial resolutions, advocating for enhanced ES management strategies

Comprehensive Analysis on the Performance and Material of Automobile Brake Discs

This article reviews the current status of automotive brake disc research and the prospects for future research. At present, the research of brake disc performance mainly includes thermal conductivity, thermal fatigue resistance, wear resistance, and brake noise. It is found that a new alloy composite, heat treatment process, ceramic composite, new structure, and new materials are emerging. At the same time, it was found that ceramic and resin were used as the matrix, fiber materials were used as reinforcements to prepare brake discs, the addition of new fillers and the study of special reinforcement materials have become new hotspots in the study of brake discs. In the future development, carbon-fiber ceramic brake discs may become the main research focus of brake discs

Performance Evaluation of Fee-Charging Policies to Reduce the Carbon Emissions of Urban Transportation in China

As a market-based instrument for transportation demand management, a transport fee-charging policy can not only effectively reduce traffic congestion, but also improve air quality. Considering the urgent need to improve urban transport fee-charging policies and reduce transport carbon emissions, the paper focuses on the role of the performance of fee-charging policies in reducing the carbon emissions of urban transport. In this study, we propose a methodological framework for the performance evaluation of urban traffic carbon emission fee-charging policies. First, we analyze the current situation of the implementation of fee-charging policies and their relationship with urban traffic congestion. Subsequently, we analyze changing trends of carbon emissions associated with transportation travel in Beijing in recent years, to identify the main sources of carbon emissions from transport. Finally, we used the DEA method to evaluate the performance of the fee policies for urban transport, which are meant to reduce carbon emissions, analyze their implementation efficiency, and then discuss the main factors affecting their efficiency. The results show that with the implementation of fee-charging policies, urban traffic congestion has eased. The overall carbon dioxide (CO2) emissions from transportation in Beijing grew rapidly. CO2 emissions generated by car travel are the main source of carbon emissions from transportation in Beijing. The average value of the overall technical efficiency (TE) of Beijing&rsquo;s fee-charging policies to reduce transportation carbon emissions from 2006 to 2018 is 0.962, indicating that the overall implementation of Beijing&rsquo;s fee-charging policies has been effective. Adjustments to the fee structure reduce motor vehicle travel to an extent, increase the proportion of green travel, and reduce the intensity of transportation carbon emissions. The technical non-efficiency in Beijing&rsquo;s fee-charging policy is mainly due to non-efficiency of scale, followed by pure technical non-efficiency. Appropriately adjusting the fee structures imposed by different policies would help to improve the efficiency of policy implementation

Adaptive Charge-Compensation-Based Variable On-Time Control to Improve Input Current Distortion for CRM Boost PFC Converter

For boost power factor correction (PFC) converters operating in critical conduction mode (CRM), charge compensation strategies are utilized to improve input current distortion. However, since massive calculations are required under complex working conditions, it is difficult to achieve accurate charge compensation with limited real-time computing resources. To solve this issue, this paper proposes an adaptive charge-compensation-based variable on-time (ACVOT) control strategy. The ACVOT controller calculates the required switching on-time by adding a fundamental value and an extended on-time. The fundamental value is adjusted by the loop compensator in each half-line cycle to provide a basic bias. The extended on-time is calculated based on partial charge compensation equation in each switching cycle to reduce the distortion. Compared with conventional digital variable on-time (VOT) control, the proposed strategy improves the input current total harmonics distortion (THD) and reduces the LUT/register resources by 54%/43% in FPGA realization. To verify the effectiveness of the proposed strategy, a 200 W prototype is built using the GaN HEMT transistor, where the THD is reduced to 1.4% at full load

Performance Evaluation of Fee-Charging Policies to Reduce the Carbon Emissions of Urban Transportation in China

As a market-based instrument for transportation demand management, a transport fee-charging policy can not only effectively reduce traffic congestion, but also improve air quality. Considering the urgent need to improve urban transport fee-charging policies and reduce transport carbon emissions, the paper focuses on the role of the performance of fee-charging policies in reducing the carbon emissions of urban transport. In this study, we propose a methodological framework for the performance evaluation of urban traffic carbon emission fee-charging policies. First, we analyze the current situation of the implementation of fee-charging policies and their relationship with urban traffic congestion. Subsequently, we analyze changing trends of carbon emissions associated with transportation travel in Beijing in recent years, to identify the main sources of carbon emissions from transport. Finally, we used the DEA method to evaluate the performance of the fee policies for urban transport, which are meant to reduce carbon emissions, analyze their implementation efficiency, and then discuss the main factors affecting their efficiency. The results show that with the implementation of fee-charging policies, urban traffic congestion has eased. The overall carbon dioxide (CO2) emissions from transportation in Beijing grew rapidly. CO2 emissions generated by car travel are the main source of carbon emissions from transportation in Beijing. The average value of the overall technical efficiency (TE) of Beijing’s fee-charging policies to reduce transportation carbon emissions from 2006 to 2018 is 0.962, indicating that the overall implementation of Beijing’s fee-charging policies has been effective. Adjustments to the fee structure reduce motor vehicle travel to an extent, increase the proportion of green travel, and reduce the intensity of transportation carbon emissions. The technical non-efficiency in Beijing’s fee-charging policy is mainly due to non-efficiency of scale, followed by pure technical non-efficiency. Appropriately adjusting the fee structures imposed by different policies would help to improve the efficiency of policy implementation