Yujing Bi

The aspA gene of Yersinia pestis exhibits a pronounced polymorphism at codon 363, with the dominant TTG allele encoding an inactive aspartate ammonia-lyase (AspA) while the GTG allele encoding an active enzyme. We previously demonstrated that this polymorphism drives an environment-dependent fitness trade-off, yet the underlying mechanism remains unclear. To address this, we first characterized the phenotypic differences between the two strains and revealed a clear growth-stress survival trade-off: the GTG (AspA-active) strain grew faster and produced more ATP, whereas the TTG (AspA-inactive) strain, despite slower growth, exhibited superior survival under nutrient limitation with oxidative, anaerobic, or hyperosmotic stress. Exogenous aspartate reversed the GTG strain’s disadvantages under anaerobic or cold stress. To dissect the metabolic basis, we performed ¹³ C-labeled metabolic flux analysis on these two strains. The GTG strain rapidly converted aspartate to fumarate via AspA, fueling the TCA cycle and boosting ATP production. In contrast, the TTG strain displayed stalled aspartate utilization and accumulated amino acids and lipids. Supplementation with TCA cycle intermediates (fumarate, succinate, or malate) partially rescued TTG growth, confirming that reduced TCA flux limits its proliferation. Collectively, AspA activity orchestrates a growth-stress survival trade-off through metabolic reprogramming, underlying the antagonistic pleiotropy of Y. pestis in aspartate-available or stressful environments. The “metabolic congestion” strategy of the TTG strain enhances survival under multiple stresses relevant to the flea gut, and it is plausible that this metabolic reprogramming may contribute to transmission and provide a selective advantage under flea-borne conditions. IMPORTANCE: The plague bacterium Yersinia pestis encounters oxidative, anaerobic, and hyperosmotic stresses—conditions relevant to its flea gut environment during transmission. This study reveals that a single, naturally occurring polymorphism in the aspA gene shifts the bacterium’s metabolism from a growth-focused mode to a “metabolic congestion” state that enhances survival under these stresses in vitro . Our work provides a mechanistic framework for understanding how metabolic reprogramming could influence adaptation to vector-like conditions, offering a plausible basis for the environment-dependent fitness trade-offs that may shape transmission dynamics.

The relationship between gut microbiota and human health has become one of the focal point in medical research. Probiotics, which modulate the gut microbiome, hold considerable promise for both prophylaxis and therapeutic intervention. This requires deeper insights into the kinetic changes and molecular mechanisms upon probiotic entry into the body. In this study, we utilized advanced molecular imaging to delineate the in vivo kinetic dynamics of two Lacticaseibacillus paracasei Zhang ( L. paracasei Zhang, LPZ) formulations: a liquid culture and a lyophilized powder. Our results provide new insights into the gastrointestinal transit and growth kinetics of the different probiotics formulations. Strikingly, the liquid LPZ achieved its peak growth phase within a relatively short period of 6 to 8 h post-ingestion, culminating in a 270- to 680-fold increase in residues at the 24th hour post-ingestion when compared to the lyophilized powder LPZ. Furthermore, during peak in vivo replication, LPZ enhanced gut microbial diversity and enriched beneficial commensal communities. Functionally, LPZ ingestion attenuated virulence factors while upregulating carbohydrate-active enzymes. Notably, LPZ significantly reduced xanthine levels, a metabolite associated with hyperuricemia, thereby providing a mechanistic basis for the observed relief from gout symptoms. This supports the mechanism of prior clinical findings and paves the way for future clinical trials and therapeutic use of LPZ and related probiotics. IMPORTANCE: The innovation of this study lies in visualizing the kinetic changes of two Lacticaseibacillus paracasei Zhang ( L. paracasei Zhang, LPZ) formulations (a liquid culture and lyophilized powder) within the gastrointestinal tract. It was found that liquid LPZ proliferates in vivo with a higher retention rate. Furthermore, we also found that when liquid LPZ reaches its peak proliferation phase in vivo , it not only effectively promotes the proliferation of other beneficial bacteria and the production of their metabolites but also generates more carbohydrate-active enzymes while reducing virulence factors, thereby amplifying the functions of LPZ. Meanwhile, we observed that liquid LPZ significantly reduces the production of xanthine in vivo , indicating its potential to lower uric acid . In light of the aforementioned findings, we herein propose the concept of “probiotikinetics.” These results provide new insights into the intake of LPZ, along with important evidence for its application in healthy populations.

Intestinal epithelial cells (IEC) are crucial for regulating intestinal local immunity to potentiate mucosal barrier function, but the mechanism remains unclear. In this study, we showed that the nicotinamide adenine dinucleotide (NAD ⁺ )‐dependent enzyme SIRT3 in IECs is required for local T cell differentiation in colorectal cancer and colitis. Modest IEC SIRT3 overexpression reduces the secretion of proinflammatory cytokine IL‐1β and inhibits IFNγ‐producing CD4 ⁺ T cells (T _H 1) and cytotoxic T lymphocytes (CTLs) differentiation. IEC SIRT3 deficiency enhances the production of IL‐1β and promotes local T _H 1 and CTL differentiation in limiting colorectal cancer growth and aggravating colitis. Mechanistically, SIRT3 deficiency promotes IEC functions through quinolinic acid (QA)‐mediated NAD ⁺ synthesis for limiting tumor growth. Microbiota‐derived 3‐hydroxyaminobenzoic acid is the source of intracellular QA in IECs. IL‐1β‐IL‐1R1 signaling is required for IEC SIRT3 deficiency‐induced T _H 1 and CTL differentiation in cancer. Thus, our findings showed that microbiota‐derived QA is used as an alternative source of replenishing the intracellular NAD ⁺ pool induced by SIRT3 deficiency to regulate IEC and T cell function, which has implications for targeting IECs as an approach to the treatment of immune‐associated diseases, including colorectal cancer and colitis.

Culturomics and 16 S rDNA sequencing were applied to identify lung tumor-resident microorganisms. In vitro characterization revealed potential functions of these cancer-associated microorganisms. Eighteen clinical lung cancer (LC) tissues samples were collected. All the samples were cultured by culturomics, and analyzed with 16 S rDNA sequencing. Four isolated isolates belonging to the genus Staphylococcus were detected to find out the possible functions in vitro. A549 cells were infected with supernatant of these bacteria, and cell index which reflected cell proliferation was determined by Real-Time Cell Analysis (RTCA). ELISA was employed to detect levels of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) in THP-1 cells stimulated with bacterial culture supernatants. A total of 12 bacteria were cultured and identified, most of which belonged to the Staphylococcus genus. Bacillus was detected through both methods. In vitro experiment, the cultured strains promoted cellular proliferation, and enhanced the levels of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) as well. Bacteria from LC tissues was isolated and identified. Lung tumor-resident microbiota was described. LC tumor-resident bacteria cause tumor development mediated by enhancing tumor cell proliferation and proinflammatory cytokines releasing by macrophages in the tumor microenvironment.

Neutrophils and macrophages are critical for antiviral immunity, but their reciprocal regulatory roles and mechanisms in the response to viral infection remain unclear. Herein, we found that the ion channel Piezo1 directs neutrophil extracellular trap (NET) formation and regulates macrophage functional differentiation in anti-influenza virus immunity. Genetic deletion of Piezo1 in neutrophils inhibited the generation of NETs and M1 macrophage differentiation while driving the development of M2 macrophages during viral infection. Piezo1-directed neutrophil NET DNA directly regulates macrophage differentiation in vitro and in vivo. Mechanistically, neutrophil Piezo1 deficiency inhibited NET DNA production, leading to decreased TLR9 and cGAS-STING signalling activity while inducing reciprocal differentiation from M1 to M2 macrophages. In addition, Piezo1 integrates magnesium signalling and the SIRT2-hypoxia-inducible factor-1 alpha (HIF1α)-dependent pathway to orchestrate reciprocal M1 and M2 macrophage lineage commitment through neutrophil-derived NET DNA. Our studies provide critical insight into the role of neutrophil-based mechanical regulation of immunopathology in directing macrophage lineage commitment during the response to influenza virus infection.

The aging process often leads to immune‐related diseases, including infections, tumors, and autoimmune disorders. Recently, researchers identified a special subpopulation of B cells in elderly female mice that increases with age and accumulates prematurely in mouse models of autoimmune diseases or viral infections; these B cells are known as age‐related B cells (ABCs). These cells possess distinctive cell surface phenotypes and transcriptional characteristics, and the cell population is widely recognized as CD11c⁺CD11b⁺T‐bet⁺CD21^‐CD23^‐ cells. Research has shown that ABCs are a heterogeneous group of B cells that originate independently of the germinal center and are insensitive to B‐cell receptor (BCR) and CD40 stimulation, differentiating and proliferating in response to toll‐like receptor 7 (TLR7) and IL‐21 stimulation. Additionally, they secrete self‐antibodies and cytokines to regulate the immune response. These issues have aroused widespread interest among researchers in this field. This review summarizes recent research progress on ABCs, including the functions and regulation of ABCs in aging, viral infection, autoimmune diseases, and organ transplantation.