Increased CD123 + HLA-DR- Granulocytes in Allergic Rhinitis and Influence of Allergens on Expression of Cell Membrane Markers.

BACKGROUND: It is reported that CD123 + HLA-DR- cells in PBMC are basophils, and CD203c, CD63, and FcεRI molecules are activation markers of basophils. However, little is known of CD123 + HLA-DR-cells in blood granulocytes. OBJECTIVE: To investigate the presence of CD123 + HLA-DR- cells in the blood granulocytes and peripheral PBMC of patients with allergic rhinitis (AR), as well as the impact of allergens on the cell membrane markers of basophils. METHODS: Flow cytometry was used to detect the expression of the membrane molecules. RESULTS: While CD123 + HLA-DR- PBMCs are representative of basophils, their presence did not significantly change in patients with AR. In contrast, both the percentage and number of CD123 + HLA-DR- granulocytes, which make up only up to 50% of basophils, were significantly increased in patients with seasonal (sAR) and perennial AR (pAR). CD63+, CD203c+, and FcεRIα+ cells within CD123 + HLA-DR- granulocytes also showed enhanced activity in patients with AR. Allergen extracts from house dust mite allergen extract (HDME) and Artemisia sieversiana wild extract further increased the number of CD123 + HLA-DR- cells in granulocytes of sAR and pAR patients, as well as in PBMCs of pAR patients. CONCLUSIONS: The use of CD123 + HLA-DR- granulocytes and PBMC may not be sufficient for diagnosing AR. Allergens could potentially contribute to the development of AR by influencing the number of CD123 + HLA-DR- cells, as well as the expression of CD63, CD203c, and FcεRIαin these cells.

Bifidobacterium pseudocatenulatum NCU-08 ameliorated senescence via modulation of the AMPK/Sirt1 signaling pathway and gut microbiota in mice.

Aging is a degenerative disease in which organisms and neurological functions decline. Emerging research has underscored the vital role of the gut microbiota in age-related processes. However, the identification of aging-associated core microbiota remains limited. In this investigation, we isolated a strain of B. pseudocatenulatum NCU-08 from the feces of centenarians and assessed its impact on aging using a mouse model induced by D-gal. Our study revealed the exceptional probiotic attributes of B. pseudocatenulatum NCU-08. Administration of B. pseudocatenulatum NCU-08 significantly ameliorated age-related memory impairment, motor dysfunction, and anxiety-like behaviors in aging mice (p < 0.01). Moreover, tissue staining analysis demonstrated that B. pseudocatenulatum NCU-08 reduced the intensity of SA-ß-gal-positive in the hippocampus of aging mice. It also reversed pathological damage and structural abnormalities in brain and intestinal tissue. B. pseudocatenulatum NCU-08 inhibited neuroinflammation induced by TLR4/NF-κB (p < 0.01) and preserved the blood-brain barrier integrity by activating the AMPK/Sirt1 pathway (p < 0.05). Furthermore, it mitigated neuronal apoptosis and oxidative stress by upregulating the PI3K/AKT signaling pathway (p < 0.01) and enhancing the activities of antioxidant enzymes, including GSH-Px (p < 0.01), SOD (p < 0.01), and CAT (p < 0.01). Besides, analysis of 16S rRNA sequencing data demonstrated that treatment with B. pseudocatenulatum NCU-08 restored intestinal microbiota homeostasis after senescence. It enhanced the abundance of beneficial bacteria while suppressing the growth of pathogenic microorganisms. In summary, our study unveiled that this novel strain of B. pseudocatenulatum NCU-08 exerts anti-aging effects through regulating the AMPK/Sirt1 pathway and intestinal microbiota. It holds promise as a functional food for promoting anti-aging effects and offers a novel approach to address aging and associated metabolic disorders.

Bifidobacterium longum SX-1326 ameliorates gastrointestinal toxicity after irinotecan chemotherapy via modulating the P53 signaling pathway and brain-gut axis.

BACKGROUND: Colorectal cancer (CRC) is a prevalent malignant malignancy affecting the gastrointestinal tract that is usually treated clinically with chemotherapeutic agents, whereas chemotherapeutic agents can cause severe gastrointestinal toxicity, which brings great pain to patients. Therefore, finding effective adjuvant agents for chemotherapy is crucial. METHODS: In this study, a CRC mouse model was successfully constructed using AOM/DSS, and the treatment was carried out by probiotic Bifidobacterium longum SX-1326 (B. longum SX-1326) in combination with irinotecan. Combining with various techniques of modern biomedical research, such as Hematoxylin and Eosin (H&E), Immunohistochemistry (IHC), Western blotting and 16S rDNA sequencing, we intend to elucidate the effect and mechanism of B. longum SX-1326 in improving the anticancer efficacy and reducing the side effects on the different levels of molecules, animals, and bacteria. RESULTS: Our results showed that B. longum SX-1326 enhanced the expression of Cleaved Caspase-3 (M vs. U = p < 0.01) and down-regulated the expression level of B-cell lymphoma-2 (Bcl-2) through up-regulation of the p53 signaling pathway in CRC mice, which resulted in an adjuvant effect on the treatment of CRC with irinotecan. Moreover, B. longum SX-1326 was also able to regulate the gut-brain-axis (GBA) by restoring damaged enterochromaffin cells, reducing the release of 5-hydroxytryptamine (5-HT) in brain tissue (I vs. U = 89.26 vs. 75.03, p < 0.05), and further alleviating the adverse effects of nausea and vomiting. In addition, B. longum SX-1326 reversed dysbiosis in CRC model mice by increasing the levels of Dehalobacterium, Ruminnococcus, and Mucispirillum. And further alleviated colorectal inflammation by downregulating the TLR4/MyD88/NF-κB signaling pathway. CONCLUSIONS: In conclusion, our work reveals that B. longum SX-1326 has a favorable effect in adjuvant irinotecan for CRC and amelioration of post-chemotherapy side effects, and also provides the theoretical basis and data for finding a safe and efficient chemotherapeutic adjuvant.

Diagnostic efficacy and safety of radial probe endobronchial ultrasound-guided transbronchial needle aspiration for adjacent lesions in segmental or subsegmental bronchi: a single-center retrospective study.

BACKGROUND: Peripheral lung lesions can be sampled using various techniques, including computer tomography-guided transthoracic needle aspiration, electromagnetic navigation bronchoscopy, virtual navigation bronchoscopy, and radial probe endobronchial ultrasound transbronchial lung biopsy. Mediastinal lesions can be sampled using techniques like convex probe endobronchial ultrasound-guided transbronchial needle aspiration (CEBUS-TBNA) and endoscopic ultrasound-fine-needle aspiration. However, effective, safe techniques for lesions adjacent to the segmental or subsegmental bronchi are lacking. Herein, we retrospectively evaluated the diagnostic yield and safety of radial probe endobronchial ultrasound-assisted transbronchial needle aspiration (REBUS-TBNA) for lesions adjacent to the segmental bronchi, and explored the factors related to diagnostic yield. METHODS: We retrospectively analyzed the diagnostic yield and safety of REBUS-TBNA cases performed in our department from January 2019 to December 2022. Observation group patients had undergone REBUS-TBNA for lesions adjacent to the segmental bronchi; control group patients had undergone CEBUS-TBNA for mediastinal or hilar lesions. Patient characteristics and lesion sizes, diagnostic yield, adverse events, and relations between diagnostic yield and clinical characteristics were analyzed. RESULTS: There were not statistically significant between-group differences in sex, age, diagnostic yield, or rate of adverse events. The observation group (n = 25; 17 male, 8 female) had a mean age of 64.76 ± 10.75 years. The average lesion size was 4.66 ± 1.07 cm, and lesions were predominantly in the upper lobes (80%). REBUS-TBNA diagnostic yield was 84%, with no adverse events reported. Diagnostic yield was not associated with lesion size or extent of bronchial stenosis; however, it was positively correlated with number of punctures. Patients with > 3 punctures had a significantly higher diagnostic yield than those with ≤ 3 punctures. CONCLUSIONS: REBUS-TBNA is a safe, effective diagnostic technique, particularly for lesions adjacent to the segmental or subsegmental bronchi of the upper lobe. Performing more than three punctures during the procedure improves the diagnostic yield. Larger-scale studies are warranted to confirm these results, and to further explore the clinical value of REBUS-TBNA.

Association between bidirectional intergenerational support and successful aging in China: Evidence from CHARLS 2018.

Aging has gradually accelerated in China, and achieving successful aging of older adults has become a public health concern. Intergenerational support is crucial for Chinese older adults in later life due to the culture of filial piety. However, the association between successful aging and intergenerational support remains poorly understood in China. This study aimed to examine the association between patterns of intergenerational support and successful aging of older adults in China. The present study is a secondary analysis of data obtained from the follow-up survey of the China Health and Retirement Longitudinal Study 2018. Data were analyzed using descriptive statistics and logistic regressions. Bidirectional intergenerational support was associated with successful aging in the participants. In addition, there was an association between different intergenerational financial, caring, and emotional support patterns and elements of successful aging.

Effects of MiR-194-5p on the proliferation and invasion of laryngeal cancer cells by regulating the expression of smurf1 and activating the mTOR signaling pathway.

Laryngeal cancer has become the focus of research because of its high incidence rate and mortality rate. However, the research on miR-194-5p in laryngeal cancer is quite rare. The purpose of this study is to explore the effect of miR-194-5p on the proliferation and invasion of laryngeal cancer cells in order to find an effective way to treat laryngeal cancer. The results showed that miR-194-5p could activate the mTOR signaling pathway by regulating the expression of Smurf1, which had an effect on laryngeal cancer cells. The results showed that the absorbance of the miR-194-5p group was 0.38 lower than that of the NC group, which indicated that up-regulation of mir-194-5p could weaken the proliferation of laryngeal cancer cells. In addition, the average number of laryngeal cancer cells in NC and the miR-194-5p groups was 125.2 and 53.8, respectively, which indicated that miR-194-5p could reduce the number of laryngeal cancer cells passing through the basement membrane and their invasion ability.

Insight into soil nitrogen and phosphorus availability and agricultural sustainability by plant growth-promoting rhizobacteria.

Nitrogen and phosphorus are critical for the vegetation ecosystem and two of the most insufficient nutrients in the soil. In agriculture practice, many chemical fertilizers are being applied to soil to improve soil nutrients and yield. This farming procedure poses considerable environmental risks which affect agricultural sustainability. As robust soil microorganisms, plant growth-promoting rhizobacteria (PGPR) have emerged as an environmentally friendly way of maintaining and improving the soil's available nitrogen and phosphorus. As a special PGPR, rhizospheric diazotrophs can fix nitrogen in the rhizosphere and promote plant growth. However, the mechanisms and influences of rhizospheric nitrogen fixation (NF) are not well researched as symbiotic NF lacks summarizing. Phosphate-solubilizing bacteria (PSB) are important members of PGPR. They can dissolve both insoluble mineral and organic phosphate in soil and enhance the phosphorus uptake of plants. The application of PSB can significantly increase plant biomass and yield. Co-inoculating PSB with other PGPR shows better performance in plant growth promotion, and the mechanisms are more complicated. Here, we provide a comprehensive review of rhizospheric NF and phosphate solubilization by PGPR. Deeper genetic insights would provide a better understanding of the NF mechanisms of PGPR, and co-inoculation with rhizospheric diazotrophs and PSB strains would be a strategy in enhancing the sustainability of soil nutrients.

Laboratory Research and Evaluation on Design and Application Performance of High-Performance Cold-Mix Resin.

To improve the safety of orthotropic steel bridge decks and the construction efficiency of bridge deck pavement by enhancing the performance of pavement materials, a new-generation, high-performance cold-mix resin was prepared by carrying out the combination of micro-characteristic analysis and performance test. Meanwhile, the pavement performance and fatigue performance of high-performance cold-mix resin mixtures and hot-mix epoxy saphalt mixtures as a control group were studied experimentally. The results show that different kinds of epoxy resins show bisphenol structure in essence. The curing exothermic peak temperature of the cold-mix resin increases with the heating rate. Both the specific heat capacity (△CP) of cold-mix resin and cold-mix resin asphalts exhibit a sudden change between -20 °C and 40 °C. In resin asphalt mixtures, cold-mix resin forms the network structure skeleton whereas the asphalt distributed in the form of tiny particles. The dosage of respective component has a significant effect on the tensile strength and elongation at break of cold-mix resin. Compared with hot-mix epoxy asphalt mixtures, cold-mix resin mixtures exhibit comparable water stability and high and low-temperature performance, as well as greater fatigue life.

Revegetation approach and plant identity unequally affect structure, ecological network and function of soil microbial community in a highly acidified mine tailings pond.

Owing to its sustainability and low cost, direct revegetation (DR) has been considered a promising alternative to capped revegetation (CR) for dealing with the serious environmental problem derived from various types of mine wastelands that are widespread in the world. However, a direct comparison of the performance of these two revegetation approaches for reclamation of extremely acidic mine wastelands and the underlying mechanisms is still lacking. To bridge this critical knowledge gap, we established 5000 m2 of vegetation on a highly acidified (pH < 3) Pb/Zn mine tailings pond employing both CR and DR schemes (2500 m2 for each scheme). We then profiled the structure, ecological network and function of soil microbial communities associated with two dominant plant species of the vegetations via high-throughput sequencing. Our results showed that CR and DR achieved a vegetation coverage of 59.7% and 90.5% within two years, respectively. This pattern was accompanied by higher concentrations of plant nutrients and lower acidification potentials in topsoils of the rhizospheres of the vegetation established by DR compared to those of CR. Revegetation approach, rather than plant identity, mostly affected the structure, ecological network and function of soil microbial community in the mine tailings pond. Rhizosphere soils of the vegetation established by DR generally had higher microbial diversity, higher relative abundances of dominant microbial phyla (e.g. Nitrospirae) that can aid plant uptake of nutrients, more complicated microbial interactive networks and more microbial genes responsible for nutrient cycling than those by CR. As the first report on a direct comparison of CR and DR schemes for reclamation of an extremely acidic mine wasteland, our study has important implications for not only the understanding of microbial ecology in revegetated mine wastelands but also the further development of sustainable revegetation schemes.

Novel phosphate-solubilizing bacteria enhance soil phosphorus cycling following ecological restoration of land degraded by mining.

Little is known about the changes in soil microbial phosphorus (P) cycling potential during terrestrial ecosystem management and restoration, although much research aims to enhance soil P cycling. Here, we used metagenomic sequencing to analyse 18 soil microbial communities at a P-deficient degraded mine site in southern China where ecological restoration was implemented using two soil ameliorants and eight plant species. Our results show that the relative abundances of key genes governing soil microbial P-cycling potential were higher at the restored site than at the unrestored site, indicating enhancement of soil P cycling following restoration. The gcd gene, encoding an enzyme that mediates inorganic P solubilization, was predominant across soil samples and was a major determinant of bioavailable soil P. We reconstructed 39 near-complete bacterial genomes harboring gcd, which represented diverse novel phosphate-solubilizing microbial taxa. Strong correlations were found between the relative abundance of these genomes and bioavailable soil P, suggesting their contributions to the enhancement of soil P cycling. Moreover, 84 mobile genetic elements were detected in the scaffolds containing gcd in the 39 genomes, providing evidence for the role of phage-related horizontal gene transfer in assisting soil microbes to acquire new metabolic potential related to P cycling.

Efficient bio-butanol production from lignocellulosic waste by elucidating the mechanisms of Clostridium acetobutylicum response to phenolic inhibitors.

Lignocellulosic biomass is considered abundant renewable feedstock to constitute a green and environmentally friendly approach for biofuels (bio-butanol) production as an effective substitute for fossil resources. However, a variety of fermentable inhibitors can be generated in hydrolysates during the biomass pretreatment process. Among them, phenolics including phenolic acids and phenolic aldehydes are the most toxic inhibitors to solventogenic clostridia for bio-butanol production. This study elucidates the physiological mechanism of Clostridium acetobutylicum ATCC 824 response to phenolic inhibitors by the integration of kinetics and transcriptional analysis. Butanol fermentations were stressed by 0.4 g/L phenolic acids or 0.4 g/L phenolic aldehydes at 12 h at the beginning of solventogenesis. With post-stress for 12 h, butanol titer was 7.01 g/L in fermentation with phenolic acid stress, while only 5.82 g/L butanol was produced in the case of phenolic aldehydes stress. Reductions in the two fermentations were 27.6% and 40.0% in comparison with the control (without stress), indicated that phenolic aldehydes had a stronger inhibitory effect on solvents synthesis in C. acetobutylicum than phenolic acids. Additionally, the transcriptional analysis revealed that phenolics altered the gene expression profiles related to membrane transporters such as ATP-binding cassette (ABC)-transporter and phosphotransferase system (PTS), glycolysis, and heat shock proteins. The lower expression levels of PTS-related genes might result in reduced glucose consumption and finally inhibited solvents synthesis under phenolic aldehydes stress. Some genes encoding histidine kinase (CA_C0323, CA_C0903, and CA_C3319) were also affected by phenolics, which might inhibit sporulation. In conclusion, our results provide valuable guidance for the construction of robust strain to efficiently produce bio-butanol from lignocellulosic biomass.

Circulating lncRNA ITSN1-2 is upregulated, and its high expression correlates with increased disease severity, elevated inflammation, and poor survival in sepsis patients.

BACKGROUND: This study aimed to assess the correlation of long noncoding (lnc) RNA intersectin (ITSN) 1-2 expression with disease risk, severity, inflammation, and survival in sepsis patients. METHODS: Three hundred and nine intensive care unit (ICU)-treated sepsis patients and 300 healthy controls were consecutively recruited in this study. Blood samples were collected from all sepsis patients within 24 hours after admitted to ICU and from healthy controls at the time of health screening, and the expression of lncRNA ITSN1-2 in plasma was detected by quantitative polymerase chain reaction. Disease severity was assessed by physicians using acute physiology and chronic health evaluation (APACHE) II score on day 1 after ICU admission. Additionally, the plasma inflammatory cytokines (including tumor necrosis factor α (TNF-α), interleukin 1ß (IL-1ß), IL-6, IL-8, IL-10, and IL-17) were measured by enzyme-linked immunosorbent assay (ELISA) kits. RESULTS: lncRNA ITSN1-2 was highly expressed in sepsis patients compared to healthy controls and could differentiate sepsis patients from healthy controls with area under the curve (AUC) 0.777 (95% CI: 0.740-0.813). lncRNA ITSN1-2 expression was positively correlated with APACHE II score, C-reactive protein (CRP), TNF-α, IL-6, and IL-8 levels, but negatively correlated with IL-10 level. In addition, lncRNA ITSN1-2 was highly expressed in non-survivors compared to survivors and could distinguish survivors from non-survivors in sepsis patients with AUC 0.654 (95% CI: 0.581-0.726). CONCLUSION: Circulating lncRNA ITSN1-2 is upregulated, and its high expression associates with increased disease severity and inflammation as well as poor prognosis in sepsis patients.

Recent advances and strategies in process and strain engineering for the production of butyric acid by microbial fermentation.

Butyric acid is an important platform chemical, which is widely used in the fields of food, pharmaceutical, energy, etc. Microbial fermentation as an alternative approach for butyric acid production is attracting great attention as it is an environmentally friendly bioprocessing. However, traditional fermentative butyric acid production is still not economically competitive compared to chemical synthesis route, due to the low titer, low productivity, and high production cost. Therefore, reduction of butyric acid production cost by utilization of alternative inexpensive feedstock, and improvement of butyric acid production and productivity has become an important target. Recently, several advanced strategies have been developed for enhanced butyric acid production, including bioprocess techniques and metabolic engineering methods. This review provides an overview of advances and strategies in process and strain engineering for butyric acid production by microbial fermentation. Additionally, future perspectives on improvement of butyric acid production are also proposed.

Hemocoagulase might not control but worsen gastrointestinal bleeding in an elderly patient with type II respiratory failure.

Hemocoagulase has been successfully used for the management of bleeding in patients undergoing surgery. Local spray of hemocoagulase during endoscopic therapy may be effective for the management of gastrointestinal bleeding. In China, intravenous infusion of hemocoagulase is given by some physicians for the treatment of gastrointestinal bleeding. However, the potential adverse events secondary to hemocoagulase, such as hypofibrinogenemia, are poorly recognized. In this paper, we reported an elderly patient with type II respiratory failure in whom hemocoagulase might induce hypofibrinogenemia and further worsen gastrointestinal bleeding. We highlighted that fibrinogen levels should be cautiously monitored in patients receiving hemocoagulase.

High-efficient n-butanol production by co-culturing Clostridium acetobutylicum and Saccharomyces cerevisiae integrated with butyrate fermentative supernatant addition.

Butanol is not only an important chemical intermediate and solvent in pharmaceutical and cosmetics industries, but also considered as an advanced biofuel. Although species of the natural host Clostridium have been engineered, butanol titers in the anaerobe seem to be limited by its intolerance to butanol less than 13 g/L. Here we aimed to develop a technology for enhancing butanol production by a co-culture system with butyrate fermentative supernatant addition. First, when adding 4.0 g/L butyrate into the acetone-butanol-ethanol (ABE) fermentation broth with single-shot at 24 h, the "acid crash" phenomenon occurred and the ABE fermentation performance deteriorated. Subsequently, we found that adding certain amino acids could effectively enhance butyrate re-assimilation, butanol tolerance and titer (from 11.1 to 14.8 g/L). Additionally, in order to decrease the raw material cost, butyrate fermentative supernatant produced by Clostridium tyrobutyricum was applied to butanol production in the Clostridium acetobutylicum/Saccharomyces cerevisiae co-culture system, instead of adding synthetic butyrate. Final butanol and total ABE concentrations reached higher levels of 16.3 and 24.8 g/L with increments of 46.8 and 37.8%, respectively. These results show that the proposed fermentation strategy has great potential for efficiently butanol production with an economic approach.

Phosphate Solubilization and Gene Expression of Phosphate-Solubilizing Bacterium Burkholderia multivorans WS-FJ9 under Different Levels of Soluble Phosphate.

Phosphate-solubilizing bacteria (PSB) have the ability to dissolve insoluble phosphate and enhance soil fertility. However, the growth and mineral phosphate solubilization of PSB could be affected by exogenous soluble phosphate and the mechanism has not been fully understood. In the present study, the growth and mineral phosphate-solubilizing characteristics of PSB strain Burkholderia multivorans WS-FJ9 were investigated at six levels of exogenous soluble phosphate (0, 0.5, 1, 5, 10, and 20 mM). The WS-FJ9 strain showed better growth at high levels of soluble phosphate. The phosphate-solubilizing activity of WS-FJ9 was reduced as the soluble phosphate concentration increased, as well as the production of pyruvic acid. Transcriptome profiling of WS-FJ9 at three levels of exogenous soluble phosphate (0, 5, and 20 mM) identified 446 differentially expressed genes, among which 44 genes were continuously up-regulated when soluble phosphate concentration was increased and 81 genes were continuously down-regulated. Some genes related to cell growth were continuously up-regulated, which would account for the better growth of WS-FJ9 at high levels of soluble phosphate. Genes involved in glucose metabolism, including glycerate kinase, 2-oxoglutarate dehydrogenase, and sugar ABC-type transporter, were continuously down-regulated, which indicates that metabolic channeling of glucose towards the phosphorylative pathway was negatively regulated by soluble phosphate. These findings represent an important first step in understanding the molecular mechanisms of soluble phosphate effects on the growth and mineral phosphate solubilization of PSB.

Regulation of Soluble Phosphate on the Ability of Phytate Mineralization and ß-Propeller Phytase Gene Expression of Pseudomonas fluorescens JZ-DZ1, a Phytate-Mineralizing Rhizobacterium.

Phytate-mineralizing rhizobacteria (PMR) play an important role in providing phosphorus for the sustainable plant growth. It is important to investigate the ability of PMR to produce phytase under different phosphate levels for its application. The effects of different concentrations of soluble phosphate on the ability of phytate mineralization of Pseudomonas fluorescens JZ-DZ1, a phytate-mineralizing rhizobacterium, were investigated in both solid and liquid media. The results on solid media showed that halo zone width gradually reduced with concentrations of soluble phosphate increasing from 0.05 to 20 mM, indicating the reduction of the ability of phytate mineralization. The results were consistent with the quantitative detection of phytase activity from the overall trend. An 1866-bp ß-propeller phytase (BPP) gene (phyPf) was cloned from the strain, and the deduced amino acid sequence of phyPf shared 98 % of identity with a known BPP from Pseudomonas sp. BS10-3 (AJF36073.1). The results of relative real-time quantitative PCR assay showed that the expression of phyPf was induced by a low concentration (0.1 mM) of soluble phosphate, suggesting that BPP secretion was regulated by gene phyPf. The BPP-harboring bacterium P. fluorescens JZ-DZ1 with low phosphate-inducible ability of phytate mineralization could be potentially applied to promote phosphorus uptake for plants in the future.

Effects of Soluble Phosphate on Phosphate-Solubilizing Characteristics and Expression of gcd Gene in Pseudomonas frederiksbergensis JW-SD2.

Phosphate-solubilizing bacteria have the ability of solubilizing mineral phosphate in soil and promoting growth of plants, but the activity of phosphate solubilization is influenced by exogenous soluble phosphate. In the present study, the effects of soluble phosphate on the activity of phosphate solubilization, acidification of media, growth, and organic acid secretion of phosphate-solubilizing bacterium Pseudomonas frederiksbergensis JW-SD2 were investigated under six levels of soluble phosphate conditions. The activity of phosphate solubilization decreased with the increase of soluble phosphate concentration, accompanying with the increase of media pH. However, the growth was promoted by adding soluble phosphate. Production of gluconic, tartaric, and oxalic acids by the strain was reduced with the increase of concentration of soluble phosphate, while acetic and pyruvic acids showed a remarkable increase. Gluconic acid predominantly produced by the strain at low levels of soluble phosphate showed that this acid was the most efficient organic acid in phosphate solubilization. Pyrroloquinoline quinone-glucose dehydrogenase gene gcd (pg5SD2) was cloned from the strain, and the expressions of pg5SD2 gene were repressed gradually with the increase of concentration of soluble phosphate. The soluble phosphate regulating the transcription of the gcd gene is speculated to underlie the regulation of the secretion of gluconic acid and subsequently the regulation of the activity of phosphate solubilization. Future research needs to consider a molecular engineering strategy to reduce the sensitivity of PSB strain to soluble phosphate via modification of the regulatory mechanism of gcd gene, which could improve the scope of PSB strains' application.