Background: The zinc uptake regulator Zur is a Zn²⁺-sensing metalloregulatory protein involved in the maintenance of bacterial zinc homeostasis. Up to now, regulation of zinc homeostasis by Zur is poorly understood in Y. pestis. Results: We constructed a zur null mutant of Y. pestis biovar microtus strain 201. Microarray expression analysis disclosed a set of 154 Zur-dependent genes of Y. pestis upon exposure to zinc rich condition. Real-time reverse transcription (RT)-PCR was subsequently used to validate the microarray data. Based on the 154 Zur-dependent genes, predicted regulatory Zur motifs were used to screen for potential direct Zur targets including three putative operons znuA, znuCB and ykgM-RpmJ2. The LacZ reporter fusion analysis verified that Zur greatly repressed the promoter activity of the above three operons. The subsequent electrophoretic mobility shift assay (EMSA) demonstrated that a purified Zur protein was able to bind to the promoter regions of the above three operons. The DNase I footprinting was used to identify the Zur binding sites for the above three operons, verifying the Zur box sequence as predicted previously in γ-Proteobacteria. The primer extension assay was further used to determine the transcription start sites for the above three operons and to localize the -10 and -35 elements. Zur binding sites overlapped the -10 sequence of its target promoters, which was consistent with the previous observation that Zur binding would block the entry of the RNA polymerase to repress the transcription of its target genes. Conclusion: Zur as a repressor directly controls the transcription of znuA, znuCB and ykgM-RpmJ2 in Y. pestis by employing a conserved mechanism of Zur-promoter DNA association as observed in γ-Proteobacteria. Zur contributes to zinc homeostasis in Y. pestis likely through transcriptional repression of the high-affinity zinc uptake system ZnuACB and two alternative ribosomal proteins YkgM and RpmJ2.

Brucellosis is one of the most common zoonoses worldwide. Subunit vaccines are promising for the prevention of human brucellosis. In our previous protective antigen screening studies, we identified a new protective antigen, BMEI0357, which belongs to the Lrp/asnC protein family, a conserved transcriptional regulator in bacteria that is absent in eukaryotes. In the present study, the Brucella genome annotation was screened and a total of 6 proteins were identified as members of the Lrp/AsnC family. Lrp/AsnC proteins have 2 domains that are conserved among the family members. However, sequence similarities between these proteins ranged from 9% to 50%, indicating high sequence heterogeneity. To test whether proteins of this family have similar characteristics, all 6 proteins were cloned and expressed in Escherichia coli. The recombinant proteins were purified and their protective efficacy was evaluated in BALB/c mice challenged with Brucella melitensis 16M. The results show that all 6 Lrp/AsnC proteins could induce a protective immune response against Brucella melitensis 16M. Antibodies against the Lrp/AsnC proteins were detected in the immunized mice. However, levels of antibodies against these proteins were relatively variable in human brucellosis sera. Taken together, our results show that these 6 proteins of the Lrp/AsnC family in Brucella could induce protective immune responses in mice.

Background: Chronic stress is associated with detrimental effects on physical health, such as chronic restraint stress (CRS), which can damage the intestinal tract. Although tryptophan has many benefits in maintaining intestinal health, the underlying mechanism of its protective effects against stress-induced intestinal injury remains unclear. Methods: In this study, we constructed a CRS model by using a behavioral restraint device in which mice were restrained for 6 h per day over 14 days and investigated the effects, as well as the potential mechanism of a high-tryptophan diet (0.4% tryptophan), on CRS-induced intestinal injury using scanning electron microscopy, 16S rRNA sequencing, and LC-MS. Results: A 0.4% tryptophan diet (fed ad libitum for 24 days) attenuated CRS-induced pathologies, including weight loss, elevated corticosterone, intestinal barrier injury, increased permeability, and epithelial apoptosis. Tryptophan modulated the gut microbiota composition in CRS-induced mice, increasing the abundance of Bacteroidota and decreasing the abundance of Firmicutes, as well as enhancing metabolic function through pathways identified by KEGG analysis. Additionally, tryptophan restored the levels of short-chain fatty acids (SCFAs), including acetic, propionic, isobutyric, butyric, and valeric acids. Correlation analyses showed interactions between tryptophan, intestinal permeability, SCFAs, and gut microbiota. Conclusions: Tryptophan supplementation attenuates CRS-induced intestinal injury by modulating intestinal barrier integrity and gut microbiota homeostasis, and the beneficial effects are largely associated with the SCFA-mediated regulation of intestinal permeability and microbiota-associated energy metabolism.

Macrophages are innate immune cells that extensively infiltrate and play a key role in the tumor microenvironment (TME). Tumor cell–secreted factors recruit monocytes into the TME, where they differentiate into tumor‐associated macrophages (TAMs), which can polarize into distinct phenotypes: M1 and M2. M1 TAMs promote antitumor immunity through cytokine secretion and antigen presentation, whereas M2 TAMs support tumor progression by facilitating angiogenesis, invasion, and immune escape. Despite these dual roles, the specific mechanisms governing macrophage plasticity and polarization remain insufficiently understood. This review comprehensively summarizes the origin, polarization, and functional diversity of macrophages in the TME, with emphasis on pathways that regulate TAM‐mediated immune responses. Furthermore, this article examines current TAM‐targeted therapeutic strategies, including recruitment inhibition, phenotypic reprogramming, and the development of chimeric antigen receptor macrophages (CAR‐Ms), as well as macrophage‐based drug delivery and exosome therapy. By integrating recent advances in cell engineering and immunometabolism, this review highlights the translational potential of TAM‐targeted therapies and their value in reshaping the immunosuppressive TME to enhance cancer immunotherapy.