[Objective] Due to the short half-life of mRNA transcript, their anti-degradation ability and ability to recruit ribosomes to initiate translation have significant effects on the gene expression in prokaryotes. However, the multiple functional regions in the 5′ end, of mRNA can affect the half-life and thus the expression of target genes, including the Shine-Dalgarno (SD) sequence and its upstream and downstream translational standby sites (TSSs) and the N-terminal coding sequence (NCS). The own and cross-regional structural differences will affect gene expression. Therefore, it is important to analyze the structure-activity relationship of each functional region. [Methods] We employed primer extension sequencing (SHAPE-seq) to analyze the structural characteristics of seven different 5′mRNAs in Escherichia coli and collected the mRNA abundance and protein level information under their regulation. [Results] Under the regulation of unstructured NCS, the mRNA abundance and protein level were increased by10 and 19 times, respectively. The formation of secondary structure TSS with a stem length of 10 nt increased the mRNA abundance. When the SD sequence was wrapped to form a secondary structure, the efficiency of translation initiation mediated by the SD sequence was affected (protein level downregulation by 10%). The combination of TSS and NCS significantly increased the mRNA abundance and protein level by 11 and 60 folds, respectively. [Conclusion] We characterized the structure of each region of 5′mRNA conducive to prokaryotic gene expression and revealed the structure-activity relationship of each functional region, providing a new regulatory element for target gene expression in industrial microorganisms.

Marine mammals mainly include Cetacea living in the water, Sirenia primarily inhabiting water, and Pinnipedia which are amphibious. All these animals are rare and included in the list of national second-class or higher protected animals. Microorganisms play crucial roles in nutrient absorption, assisting the digestive process, and enhancing immune function of mammals, being an indispensable component of the host. The unique living conditions and diets of marine mammals result in significant differences in their microbiomes compared with terrestrial mammals. As a result, our knowledge about the microbiomes derived from terrestrial mammals is not applicable to marine mammals. Therefore, understanding the structures and functions of marine mammal microbiomes is essential for comprehending the interactions between marine mammals and their living environment and enhancing conservation efforts. This paper summarizes the recent advances in research on the microbiomes of marine mammals, discusses relevant technical methods, and highlights worthy scientific issues in future research.

[Objective] To study the species and community structure of bacteria in winged and wingless Megoura crassicauda (Mordvilko). [Methods] Illumina MiSeq high-throughput sequencing was carried out for the V3−V4 variable region of bacterial 16S rRNA gene. [Results] A total of 4 746 449 sequences were obtained and annotated to 586 operational taxonomic units (OTUs) belonging to 477 species, 336 genera, 192 families, 106 orders, 46 classes of 25 phyla. Firmicutes, Actinobacteria, Proteobacteria, and Cyanobacteria were the dominant phyla in all samples. The dominant genera included Staphylococcus, Corynebacterium, and Buchnera. At the phylum level, the relative abundance of Proteobacteria, Cyanobacteria, and Deinococcus-Thermus in the winged morph was significantly higher than that in the wingless morph. At the genus level, the relative abundance of Buchnera, Exiguobacterium, Pseudomonas, Glutamicibacter, and Pseudonocardia in the winged morph was significantly higher than that in the wingless morph. [Conclusion] This study clarified the diversity and community structure of the bacteria in winged and wingless M. crassicauda and provided a reference for exploring the role of bacteria in the wing differentiation of aphids and developing new methods for pest control.

[Objective] To explore the effects of rice-crab co-culture on physicochemical indicators and microbial community structure of soil in the Yellow River irrigation area of Ningxia and thus provide a theoretical basis for promoting rice-crab farming in the Yellow River irrigation area in northwest China. [Methods] The physicochemical indicators of soil were measured, and high-throughput sequencing of 16S rRNA gene amplicons was employed to reveal the microbial community structure in the fields with only rice planting (CK) and rice-crab co-culture (EG) by introduction of crabs into the ditches around rice plots. [Results] EG had higher soil pH, total nitrogen (TN), and soil organic matter (SOM) and lower total salt content than CK from April to August. The TN, available phosphorus (AP), and SOM in EG were significantly higher than those in CK in June and July. In terms of microbial community structure characteristics, EG significantly altered the bacterial community structure in soil, increasing the bacterial diversity and abundance in April, and August. EG had higher cumulative relative abundance of the top 20 bacterial phyla than CK from April to August. The dominant phylum of both CK and EG from April to August was Proteobacteria. At the genus level, EG increased the relative abundance of Pseudomonas and decreased the relative abundance of Thiobacillus and Methanosaeta. The comparison showed that EG had stronger effect on the bacterial community structure than the sampling month. Correlation analysis shows that TN is the main factor affecting the relative abundance of soil bacteria, and it is significant (P < 0.05). [Conclusion] Compared with traditional rice monoculture (CK), sampling rice crab intercropping (EG) enhances soil fertility, increases the relative abundance of Proteobacteria and Pseudomonas in the soil, and helps improve soil fertility and nutrient cycling efficiency, as well as clean up pollutants in soil and water bodies.

Porcine deltacoronavirus (PDCoV), an emerging virus globally prevalent, causes watery diarrhea, vomiting, and dehydration of newborn piglets, posing severe economic losses in the swine industry. Moreover, with the characteristic of cross-species transmission, PDCoV can infect human and farmed animals, posing a serious threat to human health. Pyroptosis is a form of programmed cell death mediated by members of the Gasdermin family, which plays a role in defending and eliminating viruses. Coronaviruses, however, have developed precise strategies to antagonize pyroptosis and evade immune responses. This review expounds the biological characteristics of PDCoV, the process of pyroptosis, and the antagonism of Gasdermin D-mediated pyroptosis by PDCoV, aiming to enrich the knowledge about the antagonism of immune responses by PDCoV and lay a theoretical foundation for the prevention and control of this virus.

Escalating resistance of pathogens, especially Gram-negative bacteria, to antibiotics has become a public health problem arousing worldwide concern because of the abuse of antibiotics. The "Trojan Horse" strategy emerges as a promising approach to the development of new antibacterial agents. This strategy improves the antibacterial activity or broadens the antibacterial spectrum of antibiotics by using the siderophore-mediated bacterial iron transport system. In 2019, cefiderocol as the first siderophore-antibiotic conjugate was approved for marketing, which has garnered wide attention of scientists in this field. Currently, researchers mainly focus on siderophores or utilizing antibiotics with different mechanisms and ignoring linkers in the design of agents based on the "Trojan Horse" strategy. This review will summarize the impact of different linkers of conjugates on antibacterial activity, which could provide reference for the development of new antibacterial drugs and combating bacterial resistance.

[Objective] In view of the enhanced cell-to-cell spread ability of the dsbA-deleted strain (ΔdsbA) of Listeria monocytogenes, this study aims to elucidate the mechanism that how the disulfide bond formation protein DsbA mediates this biological process. [Methods] The mRNA and protein levels of virulence factors in the wild type and ΔdsbA were compared by RT-qPCR and Western blotting, respectively. The immunofluorescence co-localization analysis method was employed to observe the impact of DsbA deficiency on the actin recruitment by the virulence factor ActA in the cell-to-cell spread of L. monocytogenes (analyzing the length and quantity of the comet tails formed on one side of the bacteria by co-localization of ActA and actin). The presence or absence of interaction between DsbA and ActA was determined by isothermal titration calorimetry (ITC). [Results] Compared with the wild type, ΔdsbA showed no significant changes in the mRNA levels of virulence factors, downregulated protein levels of InlA, InlB, PlcA, and PlcB, and upregulated protein levels of ActA and LLO. In addition, ΔdsbA showed increased number and average length of comet tails, which indicated that the actin recruitment of ΔdsbA was enhanced. The ITC results revealed that DsbA bound to ActA, which gradually showed endothermic reactions, suggesting the presence of interaction between DsbA and ActA. [Conclusion] This study proved for that DsbA attenuated the recruitment ability of actin by regulating virulence proteins, thus affecting the cell-to-cell spread of L. monocytogenes. The findings help to further dissect the virulence regulatory mechanisms of L. monocytogenes during host infection, which is of great importance for controlling the contamination of zoonotic intracellular pathogens threatening public health.

[Objective] To study the effect of DNA damage response (DDR) on the replication of porcine epidemic diarrhea virus (PEDV). [Methods] Specific inhibitors were used to detect whether DDR pathway was involved in PEDV replication. The comet assay was employed to observe the DNA damage caused by PEDV infection in Vero cells. The changes in the expression levels of proteins in the DDR pathway and cell cycle of PEDV-infected Vero cells were determined by Western blotting and flow cytometry, respectively. [Results] The ATM inhibitor KU55933 significantly inhibited the replication of PEDV, with the virus titer decreasing from (5.50±0.25) log₁₀ TCID₅₀/mL to (3.15±0.15) log₁₀ TCID₅₀/mL. PEDV infection caused DNA damage in Vero cells during 12–60 h. ATM, ATR, Chk1, Chk2, and p53 were activated by PEDV infection of Vero cells. Especially, p-Chk2 and p-p53 showcased high expression during virus replication. In addition, PEDV infection led to the stagnation of Vero cells in the S phase. During virus replication, the expression of Cyclin B1 was first downregulated and then upregulated significantly. [Conclusion] PEDV perhaps utilized DNA damage pathway hijacks the ATM-Chk2 to manipulate the cell cycle and promote self-replication. The results provided a basis for elucidating the replication and infection mechanisms of PEDV and developing new potential antiviral targets.

In Pseudomonas aeruginosa, tryptophan can be converted into anthranilate via the KynABU pathway, and anthranilate as a substrate is further converted into alkyl quinolones (AQs), including 2-heptyl-3-hydroxy-4-quinolone (PQS) and 2-heptyl-4-quinolone (HHQ), under the action of pqsABCDE, a synthetic gene cluster of AQs. At the same time, anthranilate can be degraded into the tricarboxylic acid cycle under the catalysis of the anthranilate dioxygenase complex AntABC, while the biological effect of AntABC on P. aeruginosa remains unclear. [Objective] To construct and characterize the phenotype of the antABC-deleted mutant of P. aeruginosa. [Methods] With P. aeruginosa PAO1 as the starting strain, we constructed the antABC-deleted mutant by homologous recombination to study the effects of the operon on tryptophan degradation, biofilm formation, pyocyanin synthesis, motility, and virulence of P. aeruginosa. [Results] The deletion of antABC or kynU completely inhibited the growth of P. aeruginosa with tryptophan as the sole carbon source, while ΔpqsA did not present this phenotype, indicating that antABC was essential for the degradation of tryptophan by P. aeruginosa, and KynABU-AntABC pathway was the only way for the degradation of tryptophan by the bacterium under the culture conditions in this study. In addition to affecting tryptophan degradation in P. aeruginosa, the deletion of antABC promoted the biofilm formation of P. aeruginosa by inducing the expression of the extracellular polysaccharide synthesis operon pel, and it promoted the synthesis of pyocyanin by inducing the expression of the pyocyanin synthesis operons phz1 and phz2. In addition, the deletion of antABC enhanced the swarming motility and twitching motility of P. aeruginosa. Interestingly, further deletion of pqsA completely reversed the physiological phenotypes of ΔantABC. Therefore, the regulation of antABC on these physiological phenotypes depended on AQs. The deletion of antABC increased the HHQ accumulation while inhibiting the synthesis of PQS in P. aeruginosa. These results indicated that the regulation of these physiological phenotypes by antABC mainly depended on HHQ. In addition, the deletion of antABC enhanced the virulence of P. aeruginosa to Chinese cabbage and Galleria mellonella larvae, while further deletion of pqsA only partially reversed this virulence phenotype. Moreover, the deletion of antABC caused increased accumulation of anthranilate in P. aeruginosa. Therefore, the enhancement of antABC deletion on the virulence of P. aeruginosa was mediated by HHQ and anthranilate together. Finally, bioinformatics analysis revealed that the missense mutations of antABC operon occurred in more than 90% of clinical isolates of P. aeruginosa. Therefore, antABC was expected to be used as a biomarker to determine whether clinical isolates of P. aeruginosa were highly virulent. [Conclusion] AntABC plays an important role in the tryptophan degradation, biofilm formation, pyocyanin synthesis, motility, and virulence of P. aeruginosa. This finding lays a foundation for the clinical diagnosis and antimicrobial development of P. aeruginosa infection.

Nitrogen is an essential element for living organisms on Earth, and it is constantly recycled in the biosphere in different forms. A biohybrid constructed with photocatalytic materials is a new system produced in recent years, which combines photocatalytic materials with electroactive microorganisms, integrating the excellent light trapping performance of photocatalysts and the bioefficient catalytic capability. Therefore, it is of great significance to study how the system plays a role in nitrogen cycling and the related mechanisms. This paper introduces the microbial nitrogen cycling and the nitrogen cycling driven by biohybrids and details several types, advantages and disadvantages, and related mechanisms of electron transfer driven by biohybrids constructed with photocatalytic materials. Finally, this paper makes an outlook on the development prospects in this field from the natures and combinations of photocatalytic materials and microorganisms.