Peak uplift resistance of offshore slender structures shallowly buried in the sloping seabed considering wave actions

The current practice for the pipe-soil interaction mainly focuses on the pipelines which are buried in the level ground, and ocean waves are rarely considered. However, sloping topographies and wave actions are often encountered by offshore slender structures. This study numerically investigated their peak uplift resistances, taking multiple factors, i.e., the slope effect and wave effect, into account simultaneously. The numerical model was first verified by the available analytical and experimental results. It was found that the normalized peak uplift resistance decreases as the slope angle increases, especially for smaller burial ratios. The presence of wave troughs weakens the traditional peak uplift resistance. For the given burial ratio and slope angle, the reduction in the peak uplift resistance increases almost linearly with the local wave steepness. For steeper slopes and smaller burial ratios, this reduction becomes larger because of more intense upward seepage. The effects of local relative water depth and wave period were also studied. Finally, a preliminary formula for the reduction in the peak uplift resistance of shallowly-buried offshore slender structures was proposed to consider the slope effect and wave effect

Purification and Functional Characterization of a Soluble Trehalase in <i>Lissorhoptrus oryzophilus</i> (Coleoptera: Curculionidae)

Trehalase is the only enzyme known for the irreversible splitting of trehalose and plays a major role in insect growth and development. In this report, we describe a basic study of the trehalase gene fragment encoding a soluble trehalase from Lissorhoptrus oryzophilus (LoTRE1). Sequence alignment and phylogenetic analysis suggested that LoTRE1 was similar to some known insect trehalases and belongs to the Coleoptera trehalase group. Additionally, LoTRE1 was expressed mainly in the fat body. Purified protein was obtained using heterologous expression of LoTRE1 in Escherichia coli, and the recombinant protein exhibited the ability to decompose trehalose. Enzyme–substrate docking indicated the potential involvement of other residues in the catalytic activity, in addition to Asp 333. Moreover, feeding of adults on LoTRE1 dsRNA silenced the transcription of LoTRE1 and thereby reduced the activity of trehalase and increased the trehalose content; it also led to a 12% death rate. This study reveals essential molecular features of trehalase and offers insights into the structural aspects of this enzyme, which might be related to its function. Taken together, the findings demonstrate that LoTRE1 is indispensable for adults of this pest and provide a new target for the control of L. oryzophilus

Residual chlorine disrupts the microbial communities and spreads antibiotic resistance in freshwater

Chlorine disinfection is a key global public health strategy for the prevention and control of diseases, such as COVID-19. However, little is known about effects of low levels of residual chlorine on freshwater microbial communities and antibiotic resistomes. Here, we treated freshwater microcosms with continuous low concentrations of chlorine and quantified the effects on aquatic and zebrafish intestinal microbial communities and antibiotic resistomes, using shotgun metagenome and 16S rRNA gene sequencing. Although chlorine rapidly degraded, it altered the aquatic microbial community composition over time and disrupted interactions among microbes, leading to decreases in community complexity and stability. However, community diversity was unaffected. The majority of ecological functions, particularly metabolic capacities, recovered after treatment with chlorine for 14 d, due to microbial community redundancy. There were also increased levels of antibiotic-resistance gene dissemination by horizontal and vertical gene transfer under chlorine treatment. Although the zebrafish intestinal microbial community recovered from temporary dysbiosis, growth and behavior of zebrafish adults were negatively affected by chlorine. Overall, our findings demonstrate the negative effects of residual chlorine on freshwater ecosystems and highlight a possible long-term risk to public health.This study was financially supported by the consulting research project of Chinese Academy of Engineering (2020-ZD-15), National Natural Science Foundation of China (21777144, 21976161, and 41907210), and Program for Changjiang Scholars and Innovative Research Team in University (IRT_17R97).Peer reviewe

Does biological rhythm transmit from plants to rhizosphere microbes?

Plant physiological and metabolic processes are modulated by rhythmic gene expression in a large part. Meanwhile, plants are also regulated by rhizosphere microorganisms, which are fed by root exudates and provide beneficial functions to their plant host. Whether the biorhythms in plants would transfer to the rhizosphere microbial community is still uncertain and their intricate connection remains poorly understood. Here, we investigated the role of the Arabidopsis circadian clock in shaping the rhizosphere microbial community using wild-type plants and clock mutants (cca1-1 and toc1-101) with transcriptomic, metabolomic and 16S rRNA gene sequencing analysis throughout a 24-h period. Deficiencies of the central circadian clock led to abnormal diurnal rhythms for thousands of expressed genes and dozens of root exudates. The bacterial community failed to follow obvious patterns in the 24-h period, and there was lack of coordination with plant growth in the clock mutants. Our results suggest that the robust rhythmicity of genes and root exudation due to circadian clock in plants is an important driving force for the positive succession of rhizosphere communities, which will feedback on plant development.Environmental Biolog