Soil colloidal phosphorus (CP) is an active component that cannot be overlooked in the soil phosphorus cycle. Its occurrence forms and migration behavior significantly influence phosphorus bioavailability and environmental risks. This paper systematically reviews the multiscale regulatory mechanisms of microbial actions in CP transformation and migration. It focuses on chemical effects (e.g., proton secretion, iron reduction, and organic acid coordination), physical effects (e.g., extracellular polymer trapping and biofilm pore remodeling), and microbial community dynamics and molecular ecology three dimensions to elucidate how microbes drive CP activation, immobilization, and migration through interfacial reactions, functional gene expression, and community interactions. The paper further explores the synergistic effects of multiple factors on microbial regulation processes, including soil physicochemical properties, agricultural management practices, and emerging pollutants. It identifies current research gaps in cross-scale coupling, in situ characterization, and mechanism modeling, while providing theoretical foundations and research directions for enhancing soil phosphorus utilization and pollution control.

[Objective] To develop a low-cost and highly sensitive endotoxin detection reagent and detection method with recombinant horseshoe crab factor C enzymogen (rFC). [Methods] The Bac-to-Bac baculovirus expression system was used to express rFC in Sf9 cells and the activity of rFC was measured by the end-point fluorescence assay with endotoxin. The conditions of protein expression were optimized, and ion exchange was used for crude enzyme separation. An endotoxin detection method with rFC based on end-point fluorescence assay was established after the reaction conditions were optimized. Furthermore, the established method was compared with the conventional limulus amebocyte lysate (LAL). [Results] The expression level of rFC was 110.42 mg/L, increasing by 4.75 times. The linear range of endotoxin detection was 0.005-1.000 EU/mL in 1 h, with a good linearity and the limit of detection being 0.005 EU/mL. The applicability rate of this method for actual samples was 92.45%. The consistency of the detection results was 83.67%, and 89.80% of the samples had consistent detection limits with LAL. [Conclusion] This study achieves the efficient expression of rFC and establishes an endotoxin detection method with higher sensitivity than LAL, which has great potential for application.

Peptidoglycan as a key component of the bacterial cell wall is essential for maintaining bacterial morphology and osmotic stability. During normal bacterial growth, peptidoglycan is continuously remodeled through synthesis and hydrolysis, achieving a dynamic equilibrium. Peptidoglycan hydrolases play a central role in regulating peptidoglycan homeostasis, and the hydrolysis products (peptidoglycan fragments) are recycled for biosynthesis via the peptidoglycan recycling pathway. Growing evidence indicates that peptidoglycan fragments function as important signaling molecules to regulate critical physiological processes such as antibiotic resistance, endospore germination, and interspecies interactions, greatly expanding our understanding of bacterial physiological regulation. This review summarizes the major classes of bacterial peptidoglycan hydrolases and highlights recent advances in the role of peptidoglycan fragments as signaling molecules in regulating cellular processes, providing a theoretical foundation for further exploration of the multifaceted physiological functions of bacterial peptidoglycan.

[Objective] To provide a theoretical basis for developing microbiome-based ecological control strategies against citrus Huanglongbing (HLB), a devastating bacterial disease seriously threatening the global citrus industry. [Methods] Rhizosphere soil samples from both HLB-infected and healthy citrus trees in Yizhang County, Hunan Province, were investigated. Using 16S rRNA gene and ITS region amplicon sequencing, we systematically analyzed the impact mechanism of HLB on the rhizosphere micro-ecosystem. [Results] The results showed that HLB infection significantly reduced the organic matter (6.65 g/kg) and available phosphorus (7.25 mg/kg) content of the rhizosphere soil compared with that of the healthy plants, and triggered a significant decrease in the alpha diversity of bacterial communities and a significant increase in the alpha diversity of fungal communities (P<0.05). Beta diversity analysis showed that HLB significantly altered the structure of the microbial communities. Specifically, the relative abundance of pro-biotic bacteria such as Pseudomonadota and Gemmatimonadota decreased, while oligotrophic Acidobacteriota and Chloroflexota were significantly enriched. In fungal communities, the abundance of saprophytic fungi in the phyla Ascomycota and Basidiomycota increased by 5.32% and 7.38%, respectively, while the phylas Rozellomycota and Mortierellomycota decreased by 12.30% and 3.23%, respectively. HLB disrupted the rhizosphere microbial balance by inhibiting Rozellomycota, leading to excessive proliferation of saprophytic fungi and weakening the system’s disease resistance. Analysis at the order level further revealed that beneficial bacterial groups such as Burkholderiales and Hyphomicrobiales were significantly depleted, whereas stress-adaptive groups like Ktedonobacterales showed significant proliferation. PICRUSt2 analysis revealed that HLB disturbed the structure of the citrus rhizosphere bacterial community via metabolic pathways and genetic information processing. HLB also utilized saprophytic and ectomycorrhizal fungi to maintain soil health. [Conclusion] This study revealed that HLB affects soil microecological balance by remodeling the structure and function of citrus rhizosphere microorganisms, and the results may provide a theoretical basis for the development of ecological prevention and control strategies for HLB based on microbiome regulation.

Soil-borne diseases are currently the most significant type of plant disease restricting crop production and threatening food safety. The rhizosphere microbiome, often regarded as the “second genome of plants”, has shown considerable potential in controlling soil-borne crop diseases. The use of rhizosphere microbes to control soil-borne diseases offers many advantages, such as being environmentally friendly, efficient, and broadly applicable, which makes it a hot topic in rhizosphere microbe research. In this review, we first introduced rhizosphere microbes and their potential for controlling soil-borne crop diseases. Subsequently, by integrating the latest research advances, we systematically summarized seven mechanisms of microbial control against soil-borne diseases and categorized them into three pathways: (1) direct interactions between microbes and pathogens; (2) direct and indirect interactions between microbes and plants; (3) indirect interactions among microbes. Furthermore, we reviewed the current applications of the rhizosphere microbes in controlling soil-borne crop diseases. Finally, we analyzed the key research challenges in using rhizosphere microbes for soil-borne disease control and discussed potential solutions, aiming to provide references for advancing the green control of soil-borne diseases.

[Objective] As soil acidification in southwestern China becomes increasingly severe, the labile phosphorus pool is transformed into a non-labile phosphorus pool, which reduces the availability of soil phosphorus, affecting crop yield and wasting phosphate fertilizer resources. In this study, we prepared a biochar-immobilized phosphorus-solubilizing bacterial agent with biochar as the carrier and a strain capable solubilizing both organic phosphorus and inorganic phosphorus as the immobilized strain and then optimized the preparation conditions. Furthermore, this bacterial agent was evaluated in terms of the stability and the solubilizing effects on insoluble phosphorus. [Methods] Selective media were used for the isolation of phosphorus-solubilizing bacteria from plant rhizosphere soil. The molybdenum-antimony colorimetric method was employed to quantify the ability of bacteria to solubilize phosphorus. The bacterial strain was identified through physiological and biochemical tests and molecular biological analysis. The immobilized bacterial agent was prepared by the adsorption method, and the preparation conditions were optimized by single factor experiments. The prepared agent was characterized by Fourier transform infrared spectrometry and scanning electron microscopy. Furthermore, the metabolic spectrum of organic acids and phosphatase activity were qualitatively and quantitatively tested by HPLC and the fluorescence method, respectively. [Results] The strain Klebsiella sp. was isolated for immobilization, and its abilities to solubilize lecithin and tricalcium phosphate were 236.5 mg/L and 200.3 mg/L, respectively. Genome analysis showed that the strain N107 carried 27 genes related to organic and inorganic phosphorus solubilization. The optimized preparation conditions were biochar addition of 30.0 mg/mL, N107 inoculation amount of 6.0%, immobilization temperature of 30.0 ℃, and immobilization time of 12.0 h. The bacterial agent prepared under the optimal conditions increased the phosphorus-solubilizing capacity for lecithin and tricalcium phosphate by 24.0% and 22.5%, respectively, compared with the free bacterial strain. The biochar-immobilized phosphorus-solubilizing bacterial agent contained more oxygen-containing functional groups, compared with the original biochar, its total specific surface area and external surface area increased by 61.9% and 165.1%, respectively. The mechanism of phosphorus solubilization by the immobilized bacterial agent was preliminarily analyzed. The results showed that the levels of tartaric acid, citric acid, and total acids changed significantly and the activities of acid and alkaline phosphatases in the culture medium were effectively improved, although the types of organic acids secreted by the agent had no obvious changes. The structural equation model showed that pH value was closely related to phosphatase activity and organic acid content, and the immobilized bacterial agent can promote the activation of insoluble phosphorus by increasing phosphatase activity and organic acid content. [Conclusion] The immobilized phosphorus-solubilizing bacterial agent prepared in this study provides a good bioremediation material for the activation of insoluble phosphorus. This study provides an innovative perspective for developing green remediation strategies based on microbiomes.

Probiotic products have attracted increasing attention for their potential to modulate the microbiota. However, most commercial products are designed for oral administration, and their probiotic properties relevant to topical use in the reproductive tract remain insufficiently evaluated. [Objective] To assess the probiotic properties of lactic acid bacteria (LAB) derived from probiotic products, with a particular focus on their potential for topical application, thus providing scientific evidence for their use in vaginal health. [Methods] Seven common oral probiotic products (P1-P7) containing at least two different LAB species were selected from major e-commerce platforms via keyword screening, along with one clinical probiotic product (P8). LAB strains were isolated and identified from these products. We evaluated the acid tolerance, as well as the growth characteristics under different pH conditions, of the isolates by culturing them in the media of varying pH values. The antimicrobial activities of the isolates were determined via co-culture assays with pathogenic microorganisms, while hemolysis assays and genomic comparison were conducted to assess safety. [Results] The isolation rates of LAB strains from P1 to P8 were 50.0% (2/4), 0 (0/4), 66.7% (2/3), 12.5% (1/8), 33.3% (2/6), 40.0% (2/5), 0 (0/7), and 100.0% (1/1), respectively. Most strains grew well at pH 6.0-7.0, and some maintained growth at pH 4.0. Strains P4 and P8 exhibited superior acid tolerance to the others. The inhibitory effects of different strains against common vaginal pathogens varied significantly. Strains P1-2, P5-1, P6-1 and P6-2 demonstrated moderate to strong broad-spectrum inhibitory activity against all tested pathogens. Other isolated strains except P8 exhibited inhibitory activity against Gardnerellavaginalis, while strain P8 showed weak inhibitory activities against the tested pathogens. Strains P4, P5-2, P6-1, and P6-2 achieved inhibition rates exceeding 99.73% against Candidaalbicans across all three tested inoculum concentrations, and strain P5-1 reached an inhibition rate of over 94.64%. None of the strains exhibited β-hemolytic activity, and no antibiotic resistance or virulence genes were detected. [Conclusion] Several LAB isolates from commercial probiotic products exhibited notable inhibitory activities against pathogenic microorganisms and demonstrated good safety profiles. Topical administration may therefore offer greater practical value in promoting female reproductive tract health.

[Objective] Citric acid is the main metabolite of Aspergillus niger at pH≤5.0, while l-malic acid becomes the main metabolite at pH 6.0. In this study, we employed transcriptomics to analyze the differences in the expression of key genes in metabolic pathways, aiming to explore the biosynthesis mechanisms of the two organic acids. [Methods] The cells at 48 h and 72 h of the fermentation processes for citric acid and l-malic acid production were selected for transcriptomics analysis. [Results] The transcriptome data of 72 h and 48 h were compared. GO enrichment analysis showed that the upregulated genes related to the synthesis of citric acid were concentrated in carbohydrate metabolism, while those related to the synthesis of l-malic acid were concentrated in ion transport process. The acid protease genes ANI_1_62014 (aspergillin II) and ANI_1_654124 (aspartic protease pepA) showed extremely high transcription levels during citric acid synthesis, while the key genes ANI_1_2494074 [3-oxoacyl-(acyl carrier protein) synthase] and ANI_1_2488074 (biosynthetic fatty acid synthase subunit β) essential for fatty acid chain synthesis showed extremely high transcription levels in the l-malic acid synthesis pathway. The transcription level of zinc cluster transcription factor [Zn(II)₂Cys₆ transcription factor] was higher in the synthesis process of l-malic acid. HacA, AP-1, and AtfA in the bZIP family showed higher transcriptional levels in response to environmental low pH stress during citric acid synthesis. Compared with l-malic acid synthesis, citric acid synthesis was accompanied by upregulated transcription levels of ANI_1_66114 (hexokinase), ANI_1_2950014 (citrate synthase), and ANI_1_478154 (citrate transporter) and a downregulated transcription level of ANI_1_3136024 (isocitrate dehydrogenase). Efficient glycolysis, citric acid synthesis, and citric acid transport capacity and low isocitrate dehydrogenase level were the key factors for citric acid production. In the process of l-malic acid synthesis, cytoplasmic ANI_1_440184 (pyruvate carboxylase), cytoplasmic ANI_1_12134 (malate dehydrogenase), ANI_1_914104 (isocitrate lyase), and ANI_1_2040144 (malate transporter) showed upregulated transcriptional levels. The cytoplasmic rTCA pathway and glyoxylic acid carboxylation pathway were thereby determined to be the main pathways for l-malic acid synthesis. [Conclusion] This study inferred the key differential metabolic pathways for the production of citric acid and l-malic acid by analyzing integrated transcriptomic data, and screened significant differentially expressed core genes, transcription factors, and potential transporters. These results provide important clues and a theoretical basis for elucidating the regulatory mechanisms of citric acid and l-malic acid synthesis.

As a widely conserved interspecies quorum sensing signaling molecule, autoinducer-2 (AI-2) is involved in regulating various crucial physiological processes such as bioluminescence, chemotaxis, and biofilm formation. However, the effects of AI-2 on Halomonas elongata and its underlying mechanisms remain unreported. [Objective] To reveal the receptor that regulates the chemotaxis and biofilm formation of H. elongata in response to AI-2. [Methods] The quantitative capillary assay was employed to examine the chemotactic response of H. elongata to AI-2. We conducted protein domain identification, sequence alignment, and molecular docking of methyl-accepting chemotaxis proteins to identify the key amino acid sites in Tar1, the potential AI-2 receptor. The ligand-binding domain (LBD) of Tar1 and single-point mutants were expressed and purified, and the binding between Tar1-LBD and AI-2 was measured by the Vibrio harveyi MM32 bioluminescence assay. tar1 was deleted by homologous recombination, and the effects of AI-2 on the chemotaxis and biofilm formation of H. elongata were evaluated by quantitative capillary and biofilm formation assays. [Results] The quantitative capillary assay revealed that H. elongata exhibited chemotaxis to AI-2. Four methyl-accepting chemotaxis proteins were identified in H. elongata. Protein domain identification, sequence alignment, molecular docking, and V. harveyi MM32 bioluminescence assay demonstrated that Tar1-LBD bound to AI-2. The tar1-deleted mutant of H. elongata was successfully constructed by homologous recombination. The deletion of tar1 impaired the chemotaxis of H. elongata to AI-2, whereas the complementation of this gene restored the chemotaxis to level comparable to that in the wild-type. Furthermore, biofilm formation assay revealed that AI-2 enhanced the biofilm formation in H. elongatavia Tar1. [Conclusion] H. elongata exhibits chemotaxis to AI-2, and this signal molecule binds to the LBD of Tar1, thereby modulating chemotaxis and biofilm formation.

In recent years, microbially mediated mineralization, a widespread form of biomineralization in nature, has emerged as a research hotspot. This process not only exerts profound influences on mineral formation and global biogeochemical cycling but also contributes to mineral deposition within living organisms, thereby holding significant ecological and biological importance. Among microorganisms, bacteria—characterized by high metabolic activity and remarkable environmental adaptability—represent the most prominent agents in microbial mineralization. This review summarizes the mechanisms of bacteria-mediated mineralization and their applications in the biomedical field, with a particular emphasis on three principal mechanisms: bacteria-controlled mineralization, bacteria-induced mineralization, and bacteria-influenced mineralization. Furthermore, the potential applications of these processes in medical imaging, targeted therapy, and tissue engineering are discussed. The overarching aim is to provide valuable references and scientific insights to inform future research and facilitate their translation into practical applications.