Low-level bioavailable cadmium (Cd) and copper (Cu) in agricultural soils poses a severe threat to soil health and food safety; however, the mechanisms by which indigenous Cu-Cd tolerant rhizobia modulate plant-microbe-soil interactions remain poorly understood. In this field trial, the effects of two Cu-Cd tolerant strains, Sinorhizobium xinjiangense YN5 (RB) and Rhizobium pusense GF4 (RD), when inoculated individually and in combination (RC), were assessed with respect to soybean growth, heavy‑metal partitioning, rhizosphere and nodule endophytic microbiomes, and soil functional genes under bioavailable Cu-Cd stress. RB treatment significantly promoted aboveground growth parameters (plant height, node number, and pod per plant) and biomass accumulation, whereas RC treatment favored root development and maximized the reduction in soybean Cd accumulation. Rhizobia elevated Cu concentrations in leaves, while enhanced root sequestration curtailed Cd translocation to stems and pods, thereby diminishing Cd accumulation across all organs. Soil available nutrients, soil organic matter, and nitrogenase activity were significantly increased, whereas bioavailable Cd and Cu declined. Rhizobia strengthened cooperative interactions within the rhizosphere community, with positive associations accounting for 86.56% of network links under RB. Nodule symbiotic networks exhibited greater modularity and integration, and source tracking analysis revealed that RB markedly increased microbial transfer from the rhizosphere to nodules, reaching 85.2%. Rhizobia activated function associated with carbon and sulfur cycling genes. Collectively, indigenous Cu-Cd tolerant rhizobia mitigate heavy metal stress and strengthen nutrient cycling microbial functions, presenting a promising eco-compatible strategy to enhance legume productivity in agricultural soils facing low-level bioavailable heavy metal exposure.
Xinyi Li, Han-jun Liu, Tian-Bo Jia et al.· Ecotoxicology and Environmen...· 0 citations
Abstract Bacterial regulatory small RNAs (sRNAs) are integral components of posttranscriptional control, shaping environmental adaptation, metabolic homeostasis, and virulence. Advances in transcriptomics and RNA technologies have greatly expanded the repertoire of bacterial sRNAs and revealed their extensive roles in posttranscriptional regulatory networks. This review provides an updated framework for the biogenesis of bacterial sRNAs and their regulatory roles within posttranscriptional networks. Crucially, we describe the regulatory pathways controlling sRNA expression, including environmental signal sensing and regulation mediated by σ factors and transcription factors, to illustrate how sRNAs respond dynamically to changing conditions. Expanding beyond expression control, we further discuss the diverse roles of sRNA-mediated regulation in metabolic adaptation, stress responses, and bacterial virulence, emphasizing their importance in linking environmental changes to cellular phenotypes. Concurrently, we review current experimental and computational methods used for sRNA discovery and target identification. Overall, this review provides an integrated perspective on how bacterial sRNAs connect environmental sensing with adaptive cellular responses and highlights the broader significance of RNA-mediated regulation in bacterial physiology.
Zhengkai Yi, Xingning Xiao, Likou Zou et al.· FEMS Microbiology Reviews· 0 citations
This study depicted and characterized the phage-derived endolysin LysPEF52H, providing a new alternative antimicrobial strategy for controlling bacterial contamination and ensuring food safety.
The molecular weight of endolysin LysPEF52H was predicted using an online platform, and its three-dimensional (3D) structure was modeled and validated through a Ramachandran plot. Subsequently, LysPEF52H was expressed via a prokaryotic expression system, followed by purification and concentration determination. Its secondary structure and protein conformation were analyzed using circular dichroism spectroscopy and fluorescence spectroscopy. Moreover, molecular docking was used to preliminarily investigate the interactions between this endolysin and small molecules/metal ions. Finally, the physicochemical properties and antibacterial activity of LysPEF52H were examined, and its application for bacterial inactivation on chicken samples was evaluated.
The predicted molecular weight of endolysin LysPEF52H was 46808.1 Da, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis confirmed an apparent molecular weight of approximately 45 kDa. The target protein was successfully eluted using elution buffer containing 200 mmol/L imidazole, and the original concentration was quantified as 0.107 mg/mL. The secondary structure of LysPEF52H predominantly consisted of β-sheets (46%) and random coils (48%), with a minor contribution from α-helixes (6%). Conformational changes in LysPEF52H occurred between 25 °C and 45 °C, accompanied by an increase in fluorescence intensity. Above 45 ℃, the protein gradually denatured, leading to a decrease in fluorescence intensity. LysPEF52H exhibited metal ion affinity. Additionally, ʟ-alanine exhibited the strongest docking affinity to LysPEF52H. Antimicrobial spectrum assays and scanning electron microscopy demonstrated that LysPEF52H exhibited antimicrobial activity against Escherichia coli 105H and Staphylococcus aureus 8M. LysPEF52H also exhibited wide pH tolerance and good antibacterial activity after heat treatment. Its antimicrobial activity was influenced by salt concentration, metal ions, and surfactants. In addition, measurable antibacterial effects were observed on chicken artificially contaminated with E. coli 105H and S. aureus 8M treated with LysPEF52H at 4, 25, and 37 ℃.
The phage-derived endolysin LysPEF52H shows potential as an antimicrobial agent for future applications.
Jinling Wang, Yangyang Yang, Haijun Xu et al.· Food Quality and Safety· 0 citations
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