Explore the vast range of titles available.

Endosymbiont transmission via eggs to future host generations has been recognized as the main strategy for its persistence in insect hosts; however, the mechanisms for transmission have yet to be elucidated. Here, we describe the dynamic locations of Rickettsia in the ovarioles and eggs during oogenesis and embryogenesis in a globally significant pest whitefly Bemisia tabaci . Field populations of the whitefly have a high prevalence of Rickettsia , and in all Rickettsia-infected individuals, the bacterium distributes in the body cavity of the host, especially in the midgut, fat body, hemocytes, hemolymph, and near bacteriocytes. The distribution of Rickettsia was subjected to dynamic changes in the ovary during oogenesis, and our ultrastructural observations indicated that the bacteria infect host ovarioles during early developmental stages via two routes: (i) invasion of the tropharium by endocytosis and then transmission into vitellarium via nutritive cord and (ii) entry into vitellarium by hijacking bacteriocyte translocation. Most of the Rickettsia are degraded in the oocyte cytoplasm in late-stage oogenesis. However, a few reside beneath the vitelline envelope of mature eggs, spread into the embryo, and proliferate during embryogenesis to sustain high-fidelity transmission to the next generation. Our findings provide novel insights into the maternal transmission underpinning the persistence and spread of insect symbionts.

To investigate the composition, dynamic changes, and carbon sequestration effects of organic carbon in the water of Penaeus vannamei aquaculture ponds, changes in organic carbon were assessed in the water of the P. vannamei pond monoculture and integrated P. vannamei–Mercenaria mercenaria pond aquaculture systems during an aquaculture period. RDOC (refractory dissolved organic carbon) was determined using the DOC (dissolved organic carbon) degradation method, and the organic carbon composition in the water and its relationship with environmental factors were analyzed. The results showed the following: (1) The aquaculture activities significantly increased the DOC, POC (particulate organic carbon), and RDOC contents in the water and decreased the proportions of RDOC in the water. The DOC, POC, RDOC contents, and RDOC proportions in the monoculture systems were higher than those of the integrated aquaculture systems. (2) DOC, POC, RDOC contents, and RDOC proportions in the water were significantly positively correlated with chlorophyll-a contents in both aquaculture systems and significantly negatively correlated with water temperature and salinity. (3) Based on the average content and proportion of RDOC in the water of the two aquaculture systems, it was calculated that approximately an average of 108.64 kg of RDOC was present per hectare of P. vannamei aquaculture water during the aquaculture period.

The hepatopancreatic disease in shrimp has caused great economic losses in recent years, and it is necessary to identify the responsible pathogen and establish control methods. The present study aimed to identify the primary pathogenic bacteria in diseased Litopenaeus vannamei hepatopancreas (HP) and to explore the protective effects of functional bacteria on shrimp. Four pathogenic Vibrio spp. were isolated and identified from shrimp with hepatopancreatic disease, of which Vibrio harveyi HAH could be the primary pathogen causing higher rates of mortality (~ 73%) with observed symptoms. In addition, HAH had five virulence-related genes: luxR, flaB, toxR, vhhA, and vhhB. Anti-Vibrio bacterium M146 and quorum quenching (QQ) bacterium W1B were screened and used as a feed supplement. The results showed that M146 and W1B (dosed at 1.0 × 107 CFU/g) decreased the mortality of shrimp after challenge with HAH. Supplementation with M146 significantly increased the activities of alkaline phosphatase (AKP) and lysozyme (LZM), whereas supplementation with W1B had no significant effect. AKP and acid phosphatase (ACP) activities of shrimp supplemented with W1B showed a significant increase after infection with HAH, whereas a decrease in the activities of AKP and superoxide dismutase (SOD) was observed in the negative control (NC). Supplementation with M146 and W1B significantly decreased the relative messenger RNA expression of Relish and TRAF6. However, after infection with HAH, the M146 and W1B groups exhibited a different pattern of gene expression regulation compared with that in the NC group, which might suggest weakening of the virulence of the pathogen. The results suggest that these two bacteria can protect L. vannamei and that M146 not only inhibited the growth of HAH but also had an immunostimulatory effect on shrimp. On contrast, W1B did not improve the immunity of shrimp, so it is speculated that it may protect the host by affecting the quorum sensing (QS) system of pathogenic bacteria.

Aiming at the influence of water immersion in the loess stratum on the bearing capacity of the pipe gallery foundation, taking the prefabricated pipe gallery demonstration project in Xiongan New District as the research object, the static penetration test and indoor triaxial test of the foundation bearing layer of the pipe gallery before and after water immersion were carried out. In the experiment, the loss law of loess foundation bearing capacity before and after water immersion was analyzed by using the obtained soil physical index changes. The research results show that the foundation bearing capacity calculated using the static penetration test data before and after immersion are in good agreement with the field plate load test results, and the eigenvalues of the foundation bearing capacity calculated using the shear strength index are higher than the field measured results. According to the results of the static penetration test, the bearing capacity of the foundation after immersion will decrease, but the reduction range is within 4%, and there is a certain loss; the bearing capacity of the foundation before and after immersion calculated according to the shear strength index is reduced by 2.5%. It shows that the bearing capacity of the foundation will be lost to a certain extent after immersion in water, but the loss is small. It is recommended to strengthen drainage measures in the later stage to prevent the foundation from being soaked by rainwater.

Industrial farming is one of the main farming systems used for L. vannamei, and it is also the main direction of development in the future. To investigate the role of the bacterial community in nitrogen transformation in industrial L. vannamei farming systems, we studied the concentration of nitrogen compounds, the bacterial community using 16S rRNA sequencing, and nitrogen cycling genes’ abundance using absolute quantitative PCR in aquaculture water (using seawater (WD) and groundwater mixed with seawater (CY)) and analyzed the correlations between them using a person analysis. The results showed that the bacterial α-diversity index (ACE, Shannon, and Sobs) significantly changed during culture in WD but not in CY. Bacterial community species composition analysis and linear discriminant analysis effect size (LEfSe analysis) revealed that Cyanobiaceae and Microbacteriaceae were the dominant bacteria and biomarkers in WD. Vibrionaceae, Ateromonadaceae, Microbacteriaceae, Saprospiraceae, and Cryomorphaceae were the dominant bacteria and biomarkers in CY. A functional annotation of procaryotic taxa (FAPROTAX) analysis revealed that the bacterial community in WD exhibited a greater phototrophic activity at early culture stages, while at the same stage, CY exhibited strong nitrate reduction. A correlation analysis of nitrogen cycling genes and environmental factors revealed that napA, narG, ureC, amoA, and nirK were significantly correlated with the concentrations of total ammonia nitrogen (TAN), nitrite (NO2−-N), nitrate (NO3−-N), and total nitrogen (TN) in WD. In CY, amoA was positively correlated and napA and nirK were negatively correlated with TAN and TN concentrations. A correlation analysis between bacterial abundance and environmental factors revealed that Flavobacteriaceae, Saprospiraceae, Cryomorphaceae, Cyanobiaceae, Halieaceae, and Cyclobacteriaceae were significantly correlated with the concentrations of TAN and NO2−-N. The above results indicated that the bacterial community in industrial shrimp farming systems changed under different conditions, with consequent changes in the abundance of genes being involved in the nitrogen cycle and in this biogeochemical process in the water. Our study facilitates further understanding of microbes and their functions in nitrogen cycling in industrial shrimp farming systems.

The stinkbugs of the infraorder Pentatomomorpha are a group of important plant sap-feeding insects, which host diverse microorganisms. Some are located in their complex morphological midgut compartments, while some within the specialized bacteriomes of insect hosts. This perpetuation of symbioses through host generations is reinforced via the diverse routes of vertical transmission or environmental acquisition of the symbionts. These symbiotic partners, reside either through the extracellular associations in midgut or intracellular associations in specialized cells, not only have contributed nutritional benefits to the insect hosts but also shaped their ecological and evolutionary basis. The stinkbugs and gut microbe symbioses present a valuable model that provides insights into symbiotic interactions between agricultural insects and microorganisms and may become potential agents for insect pest management.

Prefabricated assembled integrated pipe corridor has the significant advantages of fast assembly, controlled quality of factory prefabricated forming, short construction period, energy saving and environmental protection compared with on-site casting. In this paper, a shallow plate load field test was carried out to test the bearing capacity of the natural foundation of the assembled pipe corridor and a numerical simulation analysis of the settlement of the substrate was carried out in combination with the typical local soft soil geological conditions, using the JXSG-6 beam making site in Gu'an South of the Beijing-Xiong Intercity Railway in Xiong’an New Area as the test site. The results of the study show that: during the vertical loading to 320 kPa, the overall displacement settlement of the foundation soil of each experimental group is small, mainly elastic deformation, and the final settlement of each test group is 6.68 mm, 10.89 mm and 5.38 mm respectively, with no cracks and no damage to the foundation soil. According to the calculation of the straight line section of the load settlement data, the average value of the foundation soil bearing capacity deformation modulus is 43.1 MPa, and the average value of the foundation stiffness of the 0.8 m diameter circular bearing plate is 78.2 MPa/m, which can provide a parameter basis for the structural design of the pipe corridor and the subsequent superstructure test calculation. However, due to the large stiffness difference between the structure of the pipe gallery and the soil, the soil settlement deformation process and the pipe gallery relative displacement, the shear effect on both sides of the pipe gallery; differential settlement under the influence of the local surface of the pipe gallery may occur tensile damage, the maximum displacement concentrated on both sides of the pit reached 0.6 mm, in the acceptable range. Therefore, the lower base of the pipe corridor has good bearing capacity and can meet the construction requirements of the installation stage of the integrated pipe corridor sections.

With the development of urban tunnels, more and more studies focus on the antiseismic design of tunnels. Setting up a shock absorption layer is a very effective means in the earthquake resistance of an urban tunnel. In this paper, in order to study the influence of the thickness of a shock absorption layer on the antiseismic effect of the urban shallow buried double arch rectangular tunnel, the Tengzhou–Fenghuang tunnel is used as the research background. Firstly, the model is established by finite element software to analyze the tunnel with 50 mm, 100 mm, and 150 mm thick shock absorption layers, and analyze the tunnel displacement, stress, and safety factors of different models under the action of a seismic wave. Finally, the calculation results are compared and analyzed with those of the model without the shock absorption layer to summarize the thickness of the shock absorption layer suitable for urban shallow buried rectangular tunnels. The results show that the displacement and stress of tunnel lining are significantly reduced, and the safety factor is significantly improved after setting the shock absorption layer. Among them, the tunnel with a 100 mm thick shock absorption layer has the greatest reduction in principal stresses, the greatest increase in safety factor, and the best antiseismic effect, while the construction costs are not high. It is recommended that the urban shallow buried double arch rectangular tunnel be constructed with a 100 mm thick shock absorption layer.

The microbial structure and metabolic potential, particularly with regard to nitrogen (N) cycling, in integrated multitrophic aquaculture (IMTA) ponds with shrimp remain unclear. In this study, an analysis of microbial community taxonomic diversity and a metagenomic analysis of N-related genes were performed in a shrimp-crab pond (Penaeus japonicus-Portunus trituberculatus, SC) and a shrimp-crab-clam pond (P. japonicus-P. trituberculatus-Sinonovacula constricta, SCC) to evaluate microbial structure and N transformation capacities in these two shrimp IMTA ponds. The composition of the microbial communities was similar between SC and SCC, but the water and sediments shared few common members in either pond. The relative abundances of N cycling genes were significantly higher in sediment than in water in both SC and SCC, except for assimilatory nitrate reduction genes. The main drivers of the differences in the relative abundances of N cycling genes in SC and SCC were salinity and pH in water and the NO2− and NH4+ contents of pore water in sediment. These results indicate that the coculture of S. constricta in a shrimp-crab pond may result in decreased N cycling in sediment. The reduced N flux in the shrimp IMTA ponds primarily originates within the sediment, except for assimilatory nitrate reduction.

Diazonium reagents functionalize single-walled carbon nanotubes suspended in aqueous solution with high selectivity and enable manipulation according to electronic structure. For example, metallic species are shown to react to the near exclusion of semiconducting nanotubes under controlled conditions. Selectivity is dictated by the availability of electrons near the Fermi level to stabilize a charge-transfer transition state preceding bond formation. The chemistry can be reversed by using a thermal treatment that restores the pristine electronic structure of the nanotube.