Neurotoxicity of dibutyl phthalate in zebrafish larvae: Decreased energy acquisition by neurons.

This work was designed to investigate the neurotoxic effects of the typical plasticizer dibutyl phthalate (DBP) using zebrafish larvae as a model. The results of exhibited that zebrafish larvae exposed to DBP at concentrations of 5 µg/L and 10 µg/L exhibited brain malformations (24 h) and behavioral abnormalities (72 h). After 72 h of exposure to DBP, microglia in the brain were over-activated, reactive oxygen species (ROS) formation was increased, and apoptosis was observed. Meanwhile, it was found that neurons exhibited impaired mitochondrial structure, absent mitochondrial membrane potential and up-regulated autophagy. Further comprehensive biochemical analyses and RNA-Seq, validated by RT-qPCR, glutamate metabolism and PPAR signaling pathway were significantly enriched in the DBP stress group, this may be the main reason for the disruption of glycolysis/gluconeogenesis processes and the reduction of energy substrates for the astrocyte-neuron lactate shuttle (ANLS). In addition, the DBP-exposed group showed aberrant activation of endoplasmic reticulum (ER) stress signaling pathway, which may be related to ROS as well as neuronal apoptosis and autophagy. In conclusion, DBP-induced neurotoxicity may be the combined result of insufficient neuronal energy acquisition, damage to mitochondrial structure, apoptosis and autophagy. These results provide a theoretical basis for understanding the neurotoxic effects of DBP.

Experiences and perspectives on the optimal timing for initiating advance care planning in patients with mild to moderate dementia: A meta-synthesis.

BACKGROUND: Advance care planning is typically initiated during the last six months of a patient's life. However, due to the progressive decline in the decision-making process in individuals with dementia, their involvement in advance care planning is limited to the early stages of the disease. Currently, there is no consensus on the optimal timing for initiating advance care planning for people with dementia, and a comprehensive review of the literature addressing this matter is lacking. OBJECTIVE: To explore the experiences and perspectives of people with dementia, their family caregivers, and health care professionals with regard to the optimal timing for initiating advance care planning. DESIGN: A meta-synthesis was conducted. DATA SOURCE: The following eight electronic databases were searched: PubMed, Embase, Web of Science, Cochrane Library, CINAHL and CNKI, WanFang and Vip. REVIEW METHODS: This review uses thematic synthesis to systematically synthesize qualitative evidence and report findings according to The Enhancing Transparency in Reporting the Synthesis of Qualitative Research (ENTREQ) and the Joanna Briggs Institute Manual for Evidence Synthesis. Study selection and data extraction were conducted independently by two researchers, and quality was evaluated using the Joanna Briggs Institute's Qualitative Research Standard Assessment tool. FINDINGS: Twenty-one studies were selected for this review. This review involved an overarching theme: The utilization of pivotal elements to transition from delayed initiation to comprehensive implementation. Three themes emerge, including the prerequisites for initiating advance care planning, not ready to start advance care planning and struggling along narrow roads. For health care professionals, the selection of an opportune moment to initiate advance care planning for people with dementia is not only a challenge but also a crucial prerequisite for the successful implementation of advance care planning. Health care professionals' experience, attitude toward advance care planning, trust relationship with patients, cultural differences among people with dementia and their caregivers, and economic disparities all influence health care professionals' judgment of the timing for initiating advance care planning. CONCLUSIONS: Determining the optimal timing for initiating advance care planning is a complex process that requires a comprehensive consideration of the realities faced by health care professionals, people with dementia and their caregivers. Therefore, it is imperative to provide relevant training to health care professionals to ensure the successful implementation of advance care planning.

Ca2+ homeostasis imbalance induced by Pparg: A key factor in di (2-ethylhexyl) phthalate (DEHP)-induced cardiac dysfunction in zebrafish larvae.

Widespread application of the typical phthalate plasticizers, di (2-ethylhexyl) phthalate (DEHP), poses a serious potential threat to the health of animals and even humans. Previous studies have confirmed the mechanism of DEHP-induced cardiac developmental defects in zebrafish larvae. However, the mechanism of cardiac dysfunction is still unclear. Thus, this work aimed to comprehensively investigate the mechanisms involved in DEHP-induced cardiac dysfunction through computational simulations, in vivo assays in zebrafish, and in vitro assays in cardiomyocytes. Firstly, molecular docking and western blot initially investigated the activating effect of DEHP on Pparg in zebrafish. Although GW9662 (PPARG antagonist) effectively alleviated DEHP-induced cardiac dysfunction and lipid metabolism disorders, it did not restore significant decreases in mitochondrial membrane potential and ATP levels. In vitro assays in cardiomyocytes, DEHP caused overexpression of PPARG and proteins involved in the regulation of Ca2+ homeostasis, and the above abnormalities were effectively alleviated by GW9662, suggesting that the Ca2+ homeostatic imbalance caused by activation of PPARG by DEHP seems to be the main cause of DEHP-induced cardiac dysfunction. To sum up, this work not only refines the mechanism of toxic effects of cardiotoxicity induced by DEHP, but provides an important theoretical basis for enriching the toxicological effects of DEHP.

Novel insights into DEHP-induced zebrafish spleen damage: Cellular apoptosis, mitochondrial dysfunction, and innate immunity.

DEHP (Di(2-ethylhexyl) phthalate) is the most abundant phthalate component detected in environmental samples as it is widely used in the manufacturing of children's toys, medical devices and furniture. Due to its wide prevalence and propensity to accumulate in the food chain, significant concerns have risen about the safety profile of DEHP. Here, we used a zebrafish model to investigate the toxicity mechanisms of DEHP. Our results indicated that exposure to DEHP altered the ROS content in zebrafish spleen and inhibited the activities of antioxidant enzymes SOD and CAT, detoxification enzyme GSH-Px and induced histopathological damage. In addition, elucidated the mechanism of DEHP significantly promoted apoptosis and caused damage in spleen cells through the bax/bcl-2 pathway. Further genetic testing demonstrated significant alterations in mitochondrial biogenesis, fission, and fusion-related genes and suggested potential mechanistic pathways, including GM10532/m6A/FIS1 axis, the STAT3/POA1 axis, and the NFR1/TFAM axis. Serological and genomic analysis indicated that DEHP exposure activated the C3 complement cascade immune pathway and interfered with innate immune function. IBRv2 analysis proposes that innate immunity may serve as a signal indicator of early toxic responses to DEHP pollutants. This study provided comprehensive cellular and genetic data for DEHP toxicity studies and emphasized the need for future management and remediation of DEHP contamination. It also provides data to specifically support the health risk assessments of DEHP, as well as contributing to broader health and environmental research.

Tissue-specific accumulation of DEHP and involvement of endogenous arachidonic acid in DEHP-induced spleen information and injury.

The plasticizer Diethylhexyl phthalate (DEHP), one of the most common contaminants, is widely detected in environmental and biological samples. However, the accumulation of DEHP in tissue and the molecular mechanisms underlying its physiological damage in the spleen of aquatic organisms have not yet been reported. In this study, gas chromatography-mass spectrometry (GC-MS), histology and multi-omics analysis were used to investigate DEHP exposure-induced alterations in transcriptomic profiles and metabolic network of zebrafish model. After exposure to DEHP, higher concentrations of DEHP were found in the intestine, liver and spleen. Anatomical and histological analyses showed that the zebrafish spleen index was significantly increased and inflammatory damage was observed. Increased splenic neutrophil counts indicate inflammation and tissue damage. Transcriptomic filtering showed that 3579 genes were significantly altered. Metabolomic analysis detected 543 differential metabolites. Multi-omics annotation results indicated that arachidonic acid and 12-Hydroperoxyicosatetraenoic acid (HPETE) are involved in the key inflammatory pathway "Inflammatory mediator regulation of TRP channels". This study demonstrated the accumulation characteristics of DEHP in aquatic zebrafish and the mechanisms of inflammation and tissue damage in the spleen which involve endogenous arachidonic acid. This will provide theoretical basis and data support for health risk assessments and tissue damage of DEHP.

Renewable fatty acid ester production in Clostridium.

Bioproduction of renewable chemicals is considered as an urgent solution for fossil energy crisis. However, despite tremendous efforts, it is still challenging to generate microbial strains that can produce target biochemical to high levels. Here, we report an example of biosynthesis of high-value and easy-recoverable derivatives built upon natural microbial pathways, leading to improvement in bioproduction efficiency. By leveraging pathways in solventogenic clostridia for co-producing acyl-CoAs, acids and alcohols as precursors, through rational screening for host strains and enzymes, systematic metabolic engineering-including elimination of putative prophages, we develop strains that can produce 20.3 g/L butyl acetate and 1.6 g/L butyl butyrate. Techno-economic analysis results suggest the economic competitiveness of our developed bioprocess. Our principles of selecting the most appropriate host for specific bioproduction and engineering microbial chassis to produce high-value and easy-separable end products may be applicable to other bioprocesses.

Co-Occurring Alteration of NOTCH and DDR Pathways Serves as Novel Predictor to Efficacious Immunotherapy in NSCLC.

Although immune checkpoint inhibitors (ICIs) have shown remarkable benefit for treatment of advanced non-small lung cancer (NSCLC), only a minority of patients can achieve durable responses and the most patients produce an ultra-rapid progressive disease. Here, we collected the availably published datasets and mined the determinants of response to immunotherapy on pathway levels. One hundred six NSCLC patients treated with immunotherapy were combined from Rizvi et al. and Hellman et al. studies (whole exon sequencing). Two independent validation datasets consisted of the MSKCC cohort (targeted sequencing) and data by Anagnostou and colleagues (whole exon sequencing). The Cancer Genome Atlas (TCGA) somatic mutation and gene expression data were applied to explore the immunobiology features. In the first combined cohort, we detected NOTCH pathway altered in 71% patients with durable clinical benefit (DCB) while only 36% among no durable benefit (NDB) (p = 0.005). Compared to NDB group, co-occurrence of NOTCH and at least two DDR (co-DDR) pathway was discovered in DCB group and contributed to a prolonged progression-free survival (PFS) [22.1 vs 3.6 months, p < 0.0001, HR, 0.34, 95% confidence interval (CI), 0.2-0.59]. In two independent datasets, co-occurrence of NOTCH+/co-DDR+ was also validated to be a better immunotherapy efficacy [Cohort 2: 13 vs 6 months, p = 0.034, HR, 0.55, 95% CI, 0.31-0.96; Cohort 3: 21 vs 11 months, p = 0.067, HR, 0.45, 95% CI, 0.18-1.1]. By analyzing TCGA cohort, we found patients with coexisting NOTCH+/co-DDR+ pathway had a higher TMB, more infiltration of CD4+T cells. Overall, co-occurrence of NOTCH and co-DDR pathway reflect a better immunotherapy efficacy in advanced NSCLC. This genomic predictor show promise in stratifying patients that suit for immunotherapy for future clinical practice.

Chromatin Accessibility Identifies Regulatory Elements Predictive of Gene Expression and Disease Outcome in Multiple Myeloma.

PURPOSE: Multiple myeloma is a malignancy of plasma cells. Extensive genetic and transcriptional characterization of myeloma has identified subtypes with prognostic and therapeutic implications. In contrast, relatively little is known about the myeloma epigenome. EXPERIMENTAL DESIGN: CD138+CD38+ myeloma cells were isolated from fresh bone marrow aspirate or the same aspirate after freezing for 1-6 months. Gene expression and chromatin accessibility were compared between fresh and frozen samples by RNA sequencing (RNA-seq) and assay for transpose accessible chromatin sequencing (ATAC-seq). Chromatin accessible regions were used to identify regulatory RNA expression in more than 700 samples from newly diagnosed patients in the Multiple Myeloma Research Foundation CoMMpass trial (NCT01454297). RESULTS: Gene expression and chromatin accessibility of cryopreserved myeloma recapitulated that of freshly isolated samples. ATAC-seq performed on a series of biobanked specimens identified thousands of chromatin accessible regions with hundreds being highly coordinated with gene expression. More than 4,700 of these chromatin accessible regions were transcribed in newly diagnosed myelomas from the CoMMpass trial. Regulatory element activity alone recapitulated myeloma gene expression subtypes, and in particular myeloma subtypes with immunoglobulin heavy chain translocations were defined by transcription of distal regulatory elements. Moreover, enhancer activity predicted oncogene expression implicating gene regulatory mechanisms in aggressive myeloma. CONCLUSIONS: These data demonstrate the feasibility of using biobanked specimens for retrospective studies of the myeloma epigenome and illustrate the unique enhancer landscapes of myeloma subtypes that are coupled to gene expression and disease progression.

Accident-related hepatic trauma in a medical clinical center in eastern China: a cross-sectional study.

BACKGROUND: The treatment of hepatic injury can be complex. Medical clinical centers are often the first line hospitals for the diagnosis and treatment of hepatic trauma in China. The aim of the study is to summarize the experience in the diagnosis and treatment of hepatic trauma in one medical clinical center in China. METHODS: This retrospective study included patients with hepatic trauma admitted between January 2002 and December 2019 at the Xishan People's Hospital of Wuxi. The outcomes were cure rate and death within 14 days post-discharge. RESULTS: Among the 318 patients with hepatic trauma, 146 patients underwent surgical treatment, and 172 received conservative treatment; three patients were transferred to other hospitals for further treatment; 283 patients were cured, and 35 died. Severe hepatic trauma occurred in 74 patients, with a mortality rate of 31.1% and accounting for 65.7% of total mortality. American Association for the Surgery of Trauma (AAST) grading ≥ III (OR = 3.51, 95%CI: 1.32-9.37, P = 0.012) and multiple organ injury (OR = 7.51, 95%CI: 2.51-22.46, P < 0.001) were independently associated with death. Among patients with AAST grading ≥ III, surgery was an independent protective factor for death (OR = 0.08, 95%CI: 0.01-0.45, P = 0.004). Among patients with ASST ≥ III and who underwent surgery, age (OR = 5.29, 95%CI: 1.37-20.33, P = 0.015) and peri-hepatic packing (PHP) (OR = 5.54, 95%CI: 1.43-21.487, P = 0.013) were independently associated with death. CONCLUSIONS: AAST grading ≥ III and multiple organ injury were independently associated with death. Among patients with AAST grading ≥ III, surgery was an independent protective factor for death. Among patients with ASST ≥ III and who underwent surgery, age and PHP were independently associated with death.

Downregulation of PA28α induces proteasome remodeling and results in resistance to proteasome inhibitors in multiple myeloma.

Protein homeostasis is critical for maintaining eukaryotic cell function as well as responses to intrinsic and extrinsic stress. The proteasome is a major portion of the proteolytic machinery in mammalian cells and plays an important role in protein homeostasis. Multiple myeloma (MM) is a plasma cell malignancy with high production of immunoglobulins and is especially sensitive to treatments that impact protein catabolism. Therapeutic agents such as proteasome inhibitors have demonstrated significant benefit for myeloma patients in all treatment phases. Here, we demonstrate that the 11S proteasome activator PA28α is upregulated in MM cells and is key for myeloma cell growth and proliferation. PA28α also regulates MM cell sensitivity to proteasome inhibitors. Downregulation of PA28α inhibits both proteasomal load and activity, resulting in a change in protein homeostasis less dependent on the proteasome and leads to cell resistance to proteasome inhibitors. Thus, our findings suggest an important role of PA28α in MM biology, and also provides a new approach for targeting the ubiquitin-proteasome system and ultimately sensitivity to proteasome inhibitors.

RRNPP-type quorum-sensing systems regulate solvent formation, sporulation and cell motility in Clostridium saccharoperbutylacetonicum.

BACKGROUND: Clostridium saccharoperbutylacetonicum N1-4 (HMT) is a strictly anaerobic, spore-forming Gram-positive bacterium capable of hyper-butanol production through the well-known acetone-butanol-ethanol fermentation process. Recently, five putative RRNPP-type QSSs (here designated as QSS1 to QSS5) were predicted in this bacterial strain, each of which comprises a putative RRNPP-type regulator (QssR1 to QssR5) and a cognate signaling peptide precursor (QssP1 to QssP5). In addition, both proteins are encoded by the same operon. The functions of these multiple RRNPP-type QSSs are unknown. RESULTS: To elucidate the function of multiple RRNPP-type QSSs as related to cell metabolism and solvent production in N1-4 (HMT), we constructed qssR-deficient mutants ΔR1, ΔR2, ΔR3 and ΔR5 through gene deletion using CRISPR-Cas9 and N1-4-dcas9-R4 (with the QssR4 expression suppressed using CRISPR-dCas9). We also constructed complementation strains by overexpressing the corresponding regulator gene. Based on systematic characterization, results indicate that QSS1, QSS2, QSS3, and QSS5 positively regulate the sol operon expression and thus solvent production, but they likely negatively regulate cell motility. Consequently, QSS4 might not directly regulate solvent production, but positively affect cell migration. In addition, QSS3 and QSS5 appear to positively regulate sporulation efficiency. CONCLUSIONS: Our study provides the first insights into the roles of multiple RRNPP-type QSSs of C. saccharoperbutylacetonicum for the regulation of solvent production, cell motility, and sporulation. Results of this study expand our knowledge of how multiple paralogous QSSs are involved in the regulation of essential bacterial metabolism pathways.

Predicting the turning points of housing prices by combining the financial model with genetic algorithm.

The turning points of housing prices play a significant role in the real estate market and economy. However, because multiple factors impact the market, the prediction of the turning points of housing prices faces significant challenges. To solve this problem, in this study, a historical data-based model that incorporates a multi-population genetic algorithm with elitism into the log-periodic power law model is proposed. This model overcomes the weaknesses of multivariate and univariate methods that it does not require any external factors while achieving excellent interpretations. We applied the model to the case study collected from housing prices in Wuhan, China, from December 2016 to October 2018. To verify its reliability, we compared the results of the proposed model to those of the log-periodic power law model optimized by the standard genetic algorithm and simulated annealing, the results of which indicate that the proposed model performs best in terms of prediction. Efficiently predicting and analyzing the housing prices will help the government promulgate effective policies for regulating the real estate market and protect home buyers.

New-onset glucose disorders in peritoneal dialysis patients: a meta-analysis and systematic review.

BACKGROUND: Peritoneal dialysis (PD) patients are at high risk of developing glucose metabolism disturbance (GMD). The incidence and prevalence of new-onset GMD, including diabetes mellitus (DM), impaired glucose tolerance (IGT) and impaired fast glucose (IFG), after initiation of PD, as well as their correlated influence factors, varies among studies in different areas and of different sample sizes. Also, the difference compared with hemodialysis (HD) remained unclear. Thus we designed this meta-analysis and systematic review to provide a full landscape of the occurrence of glucose disorders in PD patients. METHODS: We searched the MEDLINE, Embase, Web of Science and Cochrane Library databases for relevant studies through September 2018. Meta-analysis was performed on outcomes using random effects models with subgroup analysis and sensitivity analysis. RESULTS: We identified 1124 records and included 9 studies involving 13 879 PD patients. The pooled incidence of new-onset DM (NODM) was 8% [95% confidence interval (CI) 4-12; I2 = 98%] adjusted by sample sizes in PD patients. Pooled incidence rates of new-onset IGT and IFG were 15% (95% CI 3-31; I2 = 97%) and 32% (95% CI 27-37), respectively. There was no significant difference in NODM risk between PD and HD [risk ratio 0.99 (95% CI 0.69-1.40); P = 0.94; I2 = 92%]. PD patients with NODM were associated with an increased risk of mortality [hazard ratio 1.06 (95% CI 1.01-1.44); P < 0.001; I2 = 92.5%] compared with non-DM PD patients. CONCLUSIONS: Around half of PD patients may develop a glucose disorder, which can affect the prognosis by significantly increasing mortality. The incidence did not differ among different ethnicities or between PD and HD. The risk factor analysis did not draw a definitive conclusion. The glucose tolerance test should be routinely performed in PD patients.

Laparoscopic hepatectomy for the treatment of Caroli's disease: a case report.

Caroli disease is a rare congenital disorder characterized by nonobstructive dilatation of intrahepatic ducts. In cases with symptomatic intrahepatic manifestations, treatment should correspond to the type with hepatic resection for localized disease and transplantation for diffuse forms. If possible, complete resection of the cysts can cure the symptoms and avoid the risk of malignancy. A 66-year-old woman presented to Wuxi Xishan People's Hospital with recurrent intermittent upper quadrant abdominal pain. Further examinations suggested the diagnosis of Caroli disease limited to the left hepatic lobe. She underwent laparoscopic hepatectomy. Pathological examination confirmed the diagnosis of Caroli disease, and no malignancy was found. There were no immediate complications and no long-term complications after one and one-half years of follow-up. Laparoscopic hepatectomy could be a feasible, safe treatment option for localized Caroli disease.

Construction of energy-conserving sucrose utilization pathways for improving poly-γ-glutamic acid production in Bacillus amyloliquefaciens.

BACKGROUND: Sucrose is an naturally abundant and easily fermentable feedstock for various biochemical production processes. By now, several sucrose utilization pathways have been identified and characterized. Among them, the pathway consists of sucrose permease and sucrose phosphorylase is an energy-conserving sucrose utilization pathway because it consumes less ATP when comparing to other known pathways. Bacillus amyloliquefaciens NK-1 strain can use sucrose as the feedstock to produce poly-γ-glutamic acid (γ-PGA), a highly valuable biopolymer. The native sucrose utilization pathway in NK-1 strain consists of phosphoenolpyruvate-dependent phosphotransferase system and sucrose-6-P hydrolase and consumes more ATP than the energy-conserving sucrose utilization pathway. RESULTS: In this study, the native sucrose utilization pathway in NK-1 was firstly deleted and generated the B. amyloliquefaciens 3Δ strain. Then four combination of heterologous energy-conserving sucrose utilization pathways were constructed and introduced into the 3Δ strain. Results demonstrated that the combination of cscB (encodes sucrose permease) from Escherichia coli and sucP (encodes sucrose phosphorylase) from Bifidobacterium adolescentis showed the highest sucrose metabolic efficiency. The corresponding mutant consumed 49.4% more sucrose and produced 38.5% more γ-PGA than the NK-1 strain under the same fermentation conditions. CONCLUSIONS: To our best knowledge, this is the first report concerning the enhancement of the target product production by introducing the heterologous energy-conserving sucrose utilization pathways. Such a strategy can be easily extended to other microorganism hosts for reinforced biochemical production using sucrose as substrate.

Enhancing poly-γ-glutamic acid production in Bacillus amyloliquefaciens by introducing the glutamate synthesis features from Corynebacterium glutamicum.

BACKGROUND: Poly-γ-glutamic acid (γ-PGA) is a valuable polymer with glutamate as its sole precursor. Enhancement of the intracellular glutamate synthesis is a very important strategy for the improvement of γ-PGA production, especially for those glutamate-independent γ-PGA producing strains. Corynebacterium glutamicum has long been used for industrial glutamate production and it exhibits some unique features for glutamate synthesis; therefore introduction of these metabolic characters into the γ-PGA producing strain might lead to increased intracellular glutamate availability, and thus ultimate γ-PGA production. RESULTS: In this study, the unique glutamate synthesis features from C. glutamicum was introduced into the glutamate-independent γ-PGA producing Bacillus amyloliquefaciens NK-1 strain. After introducing the energy-saving NADPH-dependent glutamate dehydrogenase (NADPH-GDH) pathway, the NK-1 (pHT315-gdh) strain showed slightly increase (by 9.1%) in γ-PGA production. Moreover, an optimized metabolic toggle switch for controlling the expression of ɑ-oxoglutarate dehydrogenase complex (ODHC) was introduced into the NK-1 strain, because it was previously shown that the ODHC in C. glutamicum was completely inhibited when glutamate was actively produced. The obtained NK-PO1 (pHT01-xylR) strain showed 66.2% higher γ-PGA production than the NK-1 strain. However, the further combination of these two strategies (introducing both NADPH-GDH pathway and the metabolic toggle switch) did not lead to further increase of γ-PGA production but rather the resultant γ-PGA production was even lower than that in the NK-1 strain. CONCLUSIONS: We proposed new metabolic engineering strategies to improve the γ-PGA production in B. amyloliquefaciens. The NK-1 (pHT315-gdh) strain with the introduction of NADPH-GDH pathway showed 9.1% improvement in γ-PGA production. The NK-PO1 (pHT01-xylR) strain with the introduction of a metabolic toggle switch for controlling the expression of ODHC showed 66.2% higher γ-PGA production than the NK-1 strain. This work proposed a new strategy for improving the target product in microbial cell factories.

Improvement of levan production in Bacillus amyloliquefaciens through metabolic optimization of regulatory elements.

Levan is a functional homopolymer of fructose with considerable applications in food, pharmaceutical and cosmetic industries. To improve the levan production in Bacillus amyloliquefaciens, the regulatory elements of sacB (encoding levansucrase) expression and levansucrase secretion were optimized. Four heterologous promoters were evaluated for sacB expression, and the Pgrac promoter led to the highest level for both sacB transcription and levansucrase enzyme activity. The levan production in the corresponding recombinant strain ΔLP-pHTPgrac reached 30.5 g/L, which was 114% higher than that of the control strain NK-ΔLP. In a further step, eight signal peptides were investigated (with Pgrac as the promoter for sacB expression) for their effects on the levansucrase secretion and levan production. The signal peptide yncM was identified as the optimal one, with a secretion efficiency of approximately 90%, and the levan production in the corresponding recombinant strain ΔLP-Y reached 37.4 g/L, which was 161% higher when compared with the control strains NK-ΔLP. Finally, fed-batch fermentation was carried out in 5-L bioreactors for levan production using the recombinant strain ΔLP-Y. A final levan concentration of 102 g/L was achieved, which is very close to the ever reported highest levan production level from the literature. To our best knowledge, this is the first report of the improvement of levan production through metabolic optimization for sacB expression and levansucrase secretion. The results from this study provided essential insights for systematically metabolic engineering of microbial cell factories for enhanced biochemical production.

Mutations in genes encoding antibiotic substances increase the synthesis of poly-γ-glutamic acid in Bacillus amyloliquefaciens LL3.

Poly-γ-glutamic acid (γ-PGA) is an important natural biopolymer that is used widely in fields of foods, medicine, cosmetics, and agriculture. Several B. amyloliquefaciens LL3 mutants were constructed to improve γ-PGA synthesis via single or multiple marker-less in-frame deletions of four gene clusters (itu, bae, srf, and fen) encoding antibiotic substances. γ-PGA synthesis by the Δsrf mutant showed a slight increase (4.1 g/L) compared with that of the wild-type strain (3.3 g/L). The ΔituΔsrf mutant showed increased γ-PGA yield from 3.3 to 4.5 g/L, with an increase of 36.4%. The γ-PGA yield of the ΔituΔsrfΔfen and ΔituΔsrfΔfenΔbae mutants did not show a further increase. The four gene clusters' roles in swarming motility and biofilm formation were also studied. The Δsrf and Δbae mutant strains were both significantly defective in swarming, indicating that bacillaene and surfactin are involved in swarming motility of B. amyloliquefaciens LL3. Furthermore, Δsrf and Δitu mutant strains were obviously defective in biofilm formation; therefore, iturin and surfactin must play important roles in biofilm formation in B. amyloliquefaciens LL3.

Effects of MreB paralogs on poly-γ-glutamic acid synthesis and cell morphology in Bacillus amyloliquefaciens.

Actin-like MreB paralogs play important roles in cell shape maintenance, cell wall synthesis and the regulation of the D,L-endopeptidases, CwlO and LytE. The gram-positive bacteria, Bacillus amyloliquefaciens LL3, is a poly-γ-glutamic acid (γ-PGA) producing strain that contains three MreB paralogs: MreB, Mbl and MreBH. In B. amyloliquefaciens, CwlO and LytE can degrade γ-PGA. In this study, we aimed to test the hypothesis that modulating transcript levels of MreB paralogs would alter the synthesis and degradation of γ-PGA. The results showed that overexpression or inhibition of MreB, Mbl or MreBH had distinct effects on cell morphology and the molecular weight of the γ-PGA products. In fermentation medium, cells of mreB inhibition mutant were 50.2% longer than LL3, and the γ-PGA titer increased by 55.7%. However, changing the expression level of mbl showed only slight effects on the morphology, γ-PGA molecular weight and titer. In the mreBH inhibition mutant, γ-PGA production and its molecular weight increased by 56.7% and 19.4%, respectively. These results confirmed our hypothesis that suppressing the expression of MreB paralogs might reduce γ-PGA degradation, and that improving the cell size could strengthen γ-PGA synthesis. This is the first report of enhanced γ-PGA production via suppression of actin-like MreB paralogs.

Effects of Chromosomal Integration of the Vitreoscilla Hemoglobin Gene (vgb) and S-Adenosylmethionine Synthetase Gene (metK) on ε-Poly-L-Lysine Synthesis in Streptomyces albulus NK660.

ε-Poly-L-lysine (ε-PL) is a widely used natural food preservative. To test the effects of the Vitreoscilla hemoglobin (VHb) and S-adenosylmethionine (SAM) on ε-PL synthesis in Streptomyces albulus NK660, the heterologous VHb gene (vgb) and SAM synthetase gene (metK) were inserted into the S. albulus NK660 chromosome under the control of the constitutive ermE* promoter. CO-difference spectrum analysis showed S. albulus NK660-VHb strain could express functional VHb. S. albulus NK660-VHb produced 26.67 % higher ε-PL and 14.57 % higher biomass than the wild-type control, respectively. Reversed-phase high-pressure liquid chromatography (RP-HPLC) results showed the overexpression of the metK gene resulted in increased intracellular SAM synthesis in S. albulus NK660-SAM, which caused increases of biomass as well as the transcription level of ε-PL synthetase gene (pls). Results indicated that the expression of vgb and metK gene improved on ε-PL synthesis and biomass for S. albulus NK660, respectively.