Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 202
Filtrar
1.
Cell Rep ; 36(11): 109690, 2021 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-34525358

RESUMO

Recombinant bacterial colonization plays an indispensable role in disease prevention, alleviation, and treatment. Successful application mainly depends on whether bacteria can efficiently spatiotemporally colonize the host gut. However, a primary limitation of existing methods is the lack of precise spatiotemporal regulation, resulting in uncontrolled methods that are less effective. Herein, we design upconversion microgels (UCMs) to convert near-infrared light (NIR) into blue light to activate recombinant light-responsive bacteria (Lresb) in vivo, where autocrine "functional cellular glues" made of adhesive proteins assist Lresb inefficiently colonizing the gut. The programmable engineering platform is further developed for the controlled and effective colonization of Escherichia coli Nissle 1917 (EcN) in the gut. The colonizing bacteria effectively alleviate DSS-induced colitis in mice. We anticipate that this approach could facilitate the clinical application of engineered microbial therapeutics to accurately and effectively regulate host health.

2.
ACS Synth Biol ; 10(8): 1920-1930, 2021 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-34370452

RESUMO

Advances in synthetic biology have allowed photosynthetic cyanobacteria as promising "green cell factories" for sustainable production of biofuels and biochemicals. However, a limited of genetic switches developed in cyanobacteria restrict the complex and orthogonal metabolic regulation. In addition, suitable and controllable switches sensing and responding to specific inducers would allow for the separation of cellular growth and expression of exogenous genes or pathways that cause metabolic burden or toxicity. Here in this study, we developed a genetic switch repressed by NanR and induced by N-acetylneuraminic acid (Neu5Ac) in a fast-growing cyanobacterium Synechococcus elongatus UTEX 2973 along with its highly homologous strain S. elongatus PCC 7942. First, nanR from Escherichia coli and a previously optimized cognate promoter PJ23119H10 were introduced into Syn2973 to control the expression of the reporter gene lacZ encoding ß-galactosidase, achieving induction with negligible leakage. Second, the switch was systemically optimized to reach ∼738-fold induction by fine-tuning the expression level of NanR and introducing additional transporter of Neu5Ac. Finally, the orthogonality between the NanR/Neu5Ac switch and theophylline-responsive riboregulator was investigated, achieving a coordinated regulation or binary regulation toward the target gene. Our work here provided a new switch for transcriptional control and orthogonal regulation strategies in cyanobacteria, which would promote the metabolic regulation for the cyanobacterial chassis in the future.

3.
Waste Manag Res ; : 734242X211035943, 2021 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-34334056

RESUMO

Aiming to reveal the humification process of organic waste and its contribution to the heavy metal behaviour affected by earthworm activity, it was studied about the variation of humic acid (HA) and heavy metal behaviour during vermicomposting of the mixed pig manure and 13C-labelled rice straw. The results showed that earthworms could well adapt to the culturing environment and feed organic matter for its growth and reproduction, the vermicomposting process increased the content of humic substances (HS), HA, and fulvic acid (FA) in substrate residues, but led to less transformation of HA into FA. The elemental, ultraviolet absorption spectroscopy, Fourier transform infrared (FTIR) and fluorescence excitation-emission matrix (EEM) analysis indicated that vermicomposting led to more aromatic structures and much higher humification degree in HA, whereas less protein, FA-like substances and plastein in HA. Vermicomposting could enhance the total Cu content and decrease Cu/Zn bioavailability in the substrate residues, and vermicomposting especially can help stabilize Cu in the substrate residues by forming more complexed HA-Cu.

4.
Genes Genomics ; 43(10): 1143-1155, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34097252

RESUMO

BACKGROUND: Population stratification modeling is essential in Genome-Wide Association Studies. OBJECTIVE: In this paper, we aim to build a fine-scale population stratification model to efficiently infer individual genetic ancestry. METHODS: Kernel Principal Component Analysis (PCA) and random forest are adopted to build the population stratification model, together with parameter optimization. We explore different PCA methods, including standard PCA and kernel PCA to extract relevant features from the genotype data that is transformed by vcf2geno, a pipeline from LASER software. These extracted features are fed into a random forest for ensemble learning. Parameter tuning is performed to jointly find the optimal number of principal components, kernel function for PCA and parameters of the random forest. RESULTS: Experiments based on HGDP dataset show that kernel PCA with Sigmoid function and Gaussian function can achieve higher prediction accuracy than the standard PCA. Compared to standard PCA with the two principal components, the accuracy by using KPCA-Sigmoid with the optimal number of principal components can achieve around 100% and 200% improvement for East Asian and European populations, respectively. CONCLUSION: With the optimal parameter configuration on both PCA and random forest, our proposed method can infer the individual genetic ancestry more accurately, given their variants.

5.
BMJ Open ; 11(5): e046274, 2021 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-34011595

RESUMO

INTRODUCTION: Acute kidney injury (AKI) has high morbidity and mortality in intensive care units, which can lead to chronic kidney disease, more costs and longer hospital stay. Early identification of AKI is crucial for clinical intervention. Although various risk prediction models have been developed to identify AKI, the overall predictive performance varies widely across studies. Owing to the different disease scenarios and the small number of externally validated cohorts in different prediction models, the stability and applicability of these models for AKI in critically ill patients are controversial. Moreover, there are no current risk-classification tools that are standardised for prediction of AKI in critically ill patients. The purpose of this systematic review is to map and assess prediction models for AKI in critically ill patients based on a comprehensive literature review. METHODS AND ANALYSIS: A systematic review with meta-analysis is designed and will be conducted according to the CHecklist for critical Appraisal and data extraction for systematic Reviews of prediction Modelling Studies (CHARMS). Three databases including PubMed, Cochrane Library and EMBASE from inception through October 2020 will be searched to identify all studies describing development and/or external validation of original multivariable models for predicting AKI in critically ill patients. Random-effects meta-analyses for external validation studies will be performed to estimate the performance of each model. The restricted maximum likelihood estimation and the Hartung-Knapp-Sidik-Jonkman method under a random-effects model will be applied to estimate the summary C statistic and 95% CI. 95% prediction interval integrating the heterogeneity will also be calculated to pool C-statistics to predict a possible range of C-statistics of future validation studies. Two investigators will extract data independently using the CHARMS checklist. Study quality or risk of bias will be assessed using the Prediction Model Risk of Bias Assessment Tool. ETHICS AND DISSEMINATION: Ethical approval and patient informed consent are not required because all information will be abstracted from published literatures. We plan to share our results with clinicians and publish them in a general or critical care medicine peer-reviewed journal. We also plan to present our results at critical care international conferences. OSF REGISTRATION NUMBER: 10.17605/OSF.IO/X25AT.


Assuntos
Injúria Renal Aguda , Estado Terminal , Injúria Renal Aguda/diagnóstico , Cuidados Críticos , Humanos , Unidades de Terapia Intensiva , Metanálise como Assunto , Revisões Sistemáticas como Assunto
6.
Front Immunol ; 12: 620386, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33936035

RESUMO

Cytomegalovirus (CMV) is one of the most commonly recognized opportunistic pathogens and remains the most influential known parameter in shaping an individual's immune system. As such, T cells induced by CMV infection could have a long-term impact on subsequent immune responses. Accumulating evidence indicates that memory T cells developed during past bacterial and viral infection can cross-react with unrelated pathogens, including transplant antigens, and can alter responses to de novo infections, vaccines, cancers, or rejection. Therefore, careful examination of T cell responses elicited by CMV is warranted to understand their potentially beneficial or harmful roles in future major immune events. Our detailed exploration of the distribution, phenotype, TCR repertoire and transcriptome of CD4+ T cells within CMV seropositive healthy individuals using high-dimensional flow cytometry and single cell multi-omics sequencing reveals that CMV seropositivity has highly significant age-independent effects, leading to a reduction in CD4+ naïve T cells and an expansion of CD4+ effector memory T cells and CD45RA+ effector memory T cells. These induced CD4+ effector memory T cells undergo a specific differentiation trajectory resulting in a subpopulation of CD57+CD27-CD28-CD244+ CD4+ T cells with cytotoxic function and TCR oligoclonality for optimal controlled coexistence with cytomegalovirus. Through gene set enrichment analysis, we found that this subpopulation is similar to virus-specific CD8+ T cells and T cells that mediate acute rejection in patients using tacrolimus and belatacept, a selective costimulation blocker. Together, these data suggest that memory CD4+ T cells induced by cytomegalovirus are formed via a distinct differentiation program to acquire cytotoxic function and can be potentially detrimental to transplant patients adopting costimulation blockade immunosuppressive regimen.


Assuntos
Linfócitos T CD4-Positivos/imunologia , Diferenciação Celular/imunologia , Infecções por Citomegalovirus/imunologia , Infecções por Citomegalovirus/virologia , Citomegalovirus/imunologia , Interações Hospedeiro-Patógeno/imunologia , Abatacepte/farmacologia , Abatacepte/uso terapêutico , Adulto , Antígenos CD/metabolismo , Biomarcadores , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD4-Positivos/metabolismo , Infecções por Citomegalovirus/genética , Infecções por Citomegalovirus/metabolismo , Citotoxicidade Imunológica , Feminino , Perfilação da Expressão Gênica , Humanos , Memória Imunológica , Imunofenotipagem , Imunossupressores/farmacologia , Imunossupressores/uso terapêutico , Ativação Linfocitária/imunologia , Contagem de Linfócitos , Masculino , Pessoa de Meia-Idade , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo
7.
Methods Mol Biol ; 2290: 229-252, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34009594

RESUMO

Photosynthetic cyanobacteria are not only model organisms for studying photosynthesis and biological cycling of carbon in biosphere but also potential "green microbial factories" to produce renewable fuels and chemicals, due to their capability to utilizing solar energy and CO2. Therefore, strategies for gene regulation and carbon flux redirection are important for both fundamental research and metabolic engineering of cyanobacteria. To address the challenges, regulatory tools based on artificial small RNAs have been developed with satisfactory effects for single or multiple gene(s) regulation in various cyanobacterial species. When combined with the promoters of varying gradient strength and the inducible switches developed in recent years, it is now feasible to realize precise gene regulation in photosynthetic cyanobacteria for producing fuels and chemicals. Here in this chapter, we provide a detailed introduction of the design principles and constructing methods of the artificial sRNA tools to achieve accurate inducible regulation of cyanobacterial gene(s).


Assuntos
Cianobactérias/genética , Regulação Bacteriana da Expressão Gênica/genética , Pequeno RNA não Traduzido/síntese química , Biocombustíveis , Carbono/metabolismo , Ciclo do Carbono , Dióxido de Carbono/metabolismo , Expressão Gênica/genética , Engenharia Metabólica/métodos , Fotossíntese/fisiologia , RNA/metabolismo , Pequeno RNA não Traduzido/metabolismo , Biologia Sintética/métodos
8.
Environ Microbiol ; 23(5): 2692-2703, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33848059

RESUMO

Labelling of Type IV pili (TFP) can greatly improve our understanding of the pivotal roles of TFP in a variety of bacterial activities including motility, surface sensing and DNA-uptake etc. Here we show a simple and switchable pili-labelling method by plasmid-based inducible replacement of PilA without genetic modification in bacterial genome employed by complicated methods. Using this method, we characterized pili morphology and twitching motility of Pseudomonas aeruginosa in details. More importantly, we demonstrate its application in studying the replenishment dynamics of pilin pool of P. aeruginosa.

9.
Ecotoxicol Environ Saf ; 215: 112163, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33756288

RESUMO

Cadmium (Cd) contamination has become serious in soil and in situ stabilization technology has been widely used for heavy metal remediation. A field study was conducted to determine the effect of amendments with the doses of 3 kg/m2, including single vermicompost (A1), a 95% vermicompost mixed with 5% shell powder composite (A2) and a 95% vermicompost mixed with 5% modified shell powder composite (A3), on the Cd bioavailability, enzyme activity and bacterial community in soil, and the experiment was conducted with lettuce (Lactuca sativa L.) grown in a Cd-contaminated farmland soil. The results showed that the application of amendments increased the pH, cation exchange capacity (CEC), organic matter (OM), available nutrients, catalase (S-CAT), invertase (S-SC) and urease (S-UE) activities in soil, while significantly reduced the Cd bioavailability with the lowest Cd bioavailability being observed in the soil with A3 application. The soil bacterial richness and diversity increased after amendments application, and the bacterial community was characterized by an increase in metal-tolerant bacteria but a decrease in Proteobacteria, Acidobacteria and Gemmatimonadetes. In addition, the application of amendments significantly improved the growth of lettuce (Lactuca sativa L.) and inhibited Cd accumulation in its edible parts, especially, the Cd content in lettuce (Lactuca sativa L.) grown in soil with A3 application was below the limit of the National Food Safety Standard of China (maximum level ≤ 0.2 mg/kg). Thus, composite amendment obtained from vermicompost mixed with modified shell powder can be used as potential remediation material in Cd-contaminated soil. CAPSULE: Composite amendment obtained from vermicompost and modified shell powder had good effects on remediation of Cd-contaminated soil.


Assuntos
Cádmio/análise , Microbiologia do Solo , Poluentes do Solo/análise , Acidobacteria , Bactérias , Disponibilidade Biológica , China , Poluição Ambiental , Fazendas , Alface , Metais Pesados , Pós , Proteobactérias , Solo/química , Urease
10.
ACS Synth Biol ; 10(4): 836-846, 2021 04 16.
Artigo em Inglês | MEDLINE | ID: mdl-33779148

RESUMO

In cyanobacteria, photomixotrophic growth is considered as a promising strategy to achieve both high cell density and product accumulation. However, the conversion of glucose to acetyl coenzyme A (acetyl-CoA) in the native glycolytic pathway is insufficient, which decreases the carbon utilization and productivity of engineered cyanobacteria under photomixotrophic conditions. To increase the carbon flux from glucose to key intracellular precursor acetyl-CoA in Synechocystis sp. PCC 6803 (hereafter, Synechocystis 6803) under photomixotrophic conditions, a synthetic nonoxidative cyclic glycolysis (NOG) pathway was introduced into the wild type strain, which successfully increased the intracellular pool of acetyl-CoA by approximately 1-fold. To minimize the competition for glucose, the native Embden-Meyerhof-Parnas (EMP) and Entner-Doudoroff (ED) pathways were knocked out, respectively. Notably, eliminating the native ED pathway in the engineered strain carrying the NOG pathway further increased the intracellular pool of acetyl-CoA up to 2.8-fold. Another carbon consuming pathway in Synechocystis 6803, the glycogen biosynthesis pathway, was additionally knocked out in the above-mentioned engineered strain, which enabled an increase of the intracellular acetyl-CoA pool by up to 3.5-fold when compared with the wild type strain. Finally, the content of intracellular lipids was analyzed as an index of the productive capacity of the engineered Synechocystis 6803 cell factory under photomixotrophic conditions. The results showed the total lipids yield increased about 26% compared to the wild type (from 15.71% to 34.12%, g/g glucose), demonstrating that this integrated approach could represent a general strategy not only for the improvement of the intracellular concentration of acetyl-CoA, but also for the production of value-added chemicals that require acetyl-CoA as a key precursor in cyanobacteria.

11.
Colloids Surf B Biointerfaces ; 201: 111640, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33640676

RESUMO

Photodynamic therapy (PDT) is an exceedingly promising cancer treatment. However, the hypoxic environment in tumor and the low penetration efficiency of short-wavelength light limit the effects of PDT. In this paper, an injectable red blood cell membrane doped hydrogel system (UCNPs/S7942/RB-RHY) containing upconversion nanoparticles (UCNPs), a photosensitizer (Rose Bengal) and a strain of cyanobacteria Synechococcus elongatus PCC 7942 (S. 7942) was developed to improve the PDT effects with a good biocompatibility and biosafety. In the system, S. 7942 was capable of inexhaustibly generating oxygen triggered by the 640 nm laser irradiation for alleviating hypoxic tumor microenvironment. In addition, UCNPs converted near-infrared light to visible light upon excitation by a 980 nm laser, which further activated the photosensitizer to release reactive singlet oxygen to eradicate tumors. In vivo experiments showed that the tumor volume in the UCNPs/S7942/RB-RHY combined 640 nm with 980 nm light group was 496.9 mm3, in compared with 955.5 mm3 of the tumor volume in the group without irradiation. The results demonstrated that UCNPs/S7942/RB-RHY was able to not only dramatically alleviate tumor hypoxia but also achieve a more efficient PDT treatment. The oxygen-generating system described here provides a new idea for hypoxia-resistant cancer therapy in the future.


Assuntos
Cianobactérias , Nanopartículas , Neoplasias , Fotoquimioterapia , Linhagem Celular Tumoral , Humanos , Hidrogéis/uso terapêutico , Neoplasias/tratamento farmacológico , Fármacos Fotossensibilizantes/farmacologia , Fármacos Fotossensibilizantes/uso terapêutico , Synechococcus , Microambiente Tumoral
12.
Neuroreport ; 32(2): 99-104, 2021 01 13.
Artigo em Inglês | MEDLINE | ID: mdl-33395187

RESUMO

Sleep disorders and multiple sensory impairments have been noticed as the potential first sign of neurodegenerative diseases such as the Parkinson disease. The relationship between sleep quality and the sensory neural basis would help us consider their combination in early diagnosis. In the present study, 32 out of 45 healthy subjects' resting-state functional magnetic resonance imaging data survived from motion correction and entered into the connectivity analysis. We found that the connectivity between two regions of interest (the left olfactory gyrus and the left superior temporal pole) and the regional homogeneity in the left middle temporal gyrus were negatively correlated with their Pittsburgh sleep quality index. These results suggest that these sensory-related brain regions are related to sleep quality and they may together predict the diseases.

13.
Am J Transplant ; 21(1): 208-221, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-32519434

RESUMO

INTRODUCTION: Cytomegalovirus (CMV) remains associated with poor outcomes after kidney transplantation (kTx). The impact of belatacept on CMV infection remains understudied. In this study, we assessed the impact of belatacept on patient and graft survivals. METHODS: CMV seronegative kTx recipients were included. Patient and graft survival were studied using Kaplan-Meier method, log-rank test. Cox models were used to compare outcomes by CMV risk and immunosuppressive regimen. Incidence and persistence of CMV viremia under belatacept vs tacrolimus were compared. RESULTS: Among 308 CMV seronegative recipients, 168 CMV high-risk and 203 belatacept-treated patients were included. High-risk CMV status was associated with lower patient survival and graft survival. Among the CMV high-risk group, patients treated with belatacept presented a higher incidence of CMV viremia, a higher rate of first-line treatment failure and a longer time to virus clearance. They had a nonsignificant trend toward a lower graft survival. CONCLUSION: Belatacept-based maintenance immunosuppression is associated with an increased risk of CMV primary-infection and a prolonged course of viral replication in CMV high-risk patients. Further studies are needed to confirm the nonsignificant trend towards a lower graft survival in CMV high-risk patients treated with belatacept and whether it is explained by the higher risk of CMV reactivation and infection.


Assuntos
Infecções por Citomegalovirus , Transplante de Rim , Abatacepte/uso terapêutico , Infecções por Citomegalovirus/tratamento farmacológico , Infecções por Citomegalovirus/epidemiologia , Rejeição de Enxerto/tratamento farmacológico , Rejeição de Enxerto/etiologia , Rejeição de Enxerto/prevenção & controle , Sobrevivência de Enxerto , Humanos , Imunossupressores/uso terapêutico , Transplante de Rim/efeitos adversos , Fatores de Risco , Transplantados
14.
Biochim Biophys Acta Bioenerg ; 1862(1): 148336, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-33181099

RESUMO

High light (HL) exposure leads to photoinhibition and excess accumulation of toxic reactive oxygen species (ROS) in photosynthetic organisms, negatively impacting the global primary production. In this study, by screening a mutant library, a gene related with bicarbonate transport, slr1512, was found involved in HL acclimation in model cyanobacterium Synechocystis sp. PCC 6803. Comparative growth analysis showed that the slr1512 knockout mutant dramatically enhanced the tolerance of Synechocystis towards long-term HL stress (200 µmol photons m-2 s-1) than the wild type, achieving an enhanced growth by ~1.95-folds after 10 d. The phenotype differences between Δslr1512 and the wild type were analyzed via absorption spectrum and chlorophyll a content measurement. In addition, the accessible bicarbonate controlled by slr1512 and decreased PSII activity were demonstrated, and they were found to be the key factors affecting the tolerance of Synechocystis against HL stress. Further analysis confirmed that intracellular bicarbonate can significantly affect the activity of photosystem II, leading to the altered accumulation of toxic ROS under HL. Finally, a comparative transcriptomics was applied to determine the differential responses to HL between Δslr1512 and the wild type. This work provides useful insights to long-term acclimation mechanisms towards HL and valuable information to guide the future tolerance engineering of cyanobacteria against HL.


Assuntos
Aclimatação , Proteínas de Bactérias/metabolismo , Bicarbonatos/metabolismo , Luz , Proteínas de Membrana Transportadoras/metabolismo , Estresse Fisiológico , Synechocystis/metabolismo , Proteínas de Bactérias/genética , Clorofila A/genética , Clorofila A/metabolismo , Regulação Bacteriana da Expressão Gênica , Concentração de Íons de Hidrogênio , Proteínas de Membrana Transportadoras/genética , Synechocystis/genética
15.
Sci Total Environ ; 761: 144111, 2021 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-33352345

RESUMO

Environmental pollution caused by heavy metals has received worldwide attentions due to their ubiquity, poor degradability and easy bioaccumulation in host cells. As one potential solution, photosynthetic cyanobacteria have been considered as promising remediation chassis and widely applied in various bioremediation processes of heavy-metals. Meanwhile, deciphering resistant mechanisms and constructing tolerant chassis towards heavy metals could greatly contribute to the successful application of the cyanobacteria-based bioremediation in the future. In this review, first we summarized recent application of cyanobacteria in heavy metals bioremediation using either live or dead cells. Second, resistant mechanisms and strategies for enhancing cyanobacterial bioremediation of heavy metals were discussed. Finally, potential challenges and perspectives for improving bioremediation of heavy metals by cyanobacteria were presented.


Assuntos
Cianobactérias , Metais Pesados , Biodegradação Ambiental , Fotossíntese
16.
Sheng Wu Gong Cheng Xue Bao ; 36(10): 2126-2138, 2020 Oct 25.
Artigo em Chinês | MEDLINE | ID: mdl-33169577

RESUMO

Development of "liquid sunshine" could be a key technology to deal with the issue of fossil fuel depletion. ß-caryophyllene is a terpene compound with high energy density and has attracted attention for its potential application as a jet fuel. The high temperature and high light-tolerant photosynthetic cyanobacterium Synechococcus elongatus UTEX 2973 (hereafter Synechococcus 2973), whose doubling time is as short as 1.5 h, has great potential for synthesizing ß-caryophyllene using sunlight and CO2. In this study, a production of ~121.22 µg/L ß-caryophyllene was achieved at 96 h via a combined strategy of pathway construction, key enzyme optimization and precursor supply enhancement. In addition, a final production of ~212.37 µg/L at 96 h was realized in a high-density cultivation. To our knowledge, this is the highest production reported for ß-caryophyllene using cyanobacterial chassis and our study provide important basis for high-density fuel synthesis in cyanobacteria.


Assuntos
Biocombustíveis , Dióxido de Carbono , Synechococcus , Biocombustíveis/microbiologia , Dióxido de Carbono/metabolismo , Luz , Fotossíntese , Synechococcus/genética , Synechococcus/metabolismo , Synechococcus/efeitos da radiação
17.
Front Microbiol ; 11: 566117, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33117313

RESUMO

myo-inositol (MI) is an essential growth factor, nutritional source, and important precursor for many derivatives like D-chiro-inositol. In this study, attempts were made to achieve the "green biosynthesis" of MI in a model photosynthetic cyanobacterium Synechocystis sp. PCC 6803. First, several genes encoding myo-inositol-1-phosphate synthases and myo-inositol-1-monophosphatase, catalyzing the first or the second step of MI synthesis, were introduced, respectively, into Synechocystis. The results showed that the engineered strain carrying myo-inositol-1-phosphate synthase gene from Saccharomyces cerevisiae was able to produce MI at 0.97 mg L-1. Second, the combined overexpression of genes related to the two catalyzing processes increased the production up to 1.42 mg L-1. Third, to re-direct more cellular carbon flux into MI synthesis, an inducible small RNA regulatory tool, based on MicC-Hfq, was utilized to control the competing pathways of MI biosynthesis, resulting in MI production of ∼7.93 mg L-1. Finally, by optimizing the cultivation condition via supplying bicarbonate to enhance carbon fixation, a final MI production up to 12.72 mg L-1 was achieved, representing a ∼12-fold increase compared with the initial MI-producing strain. This study provides a light-driven green synthetic strategy for MI directly from CO2 in cyanobacterial chassis and represents a renewable alternative that may deserve further optimization in the future.

18.
Metab Eng ; 61: 275-287, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32707168

RESUMO

With the ability to recycle CO2 into value-added chemicals, cyanobacteria have been considered as renewable microbial cell factories. Astaxanthin, a highly valued carotenoid with potent antioxidant activity, could be beneficial to human health. Astaxanthin biosynthesis in engineered chassis has been achieved previously, but it generated a relatively low yield. Here, we successfully constructed a highly efficient astaxanthin biosynthetic pathway in cyanobacterium Synechocystis sp. PCC 6803, and achieved more than a 500-fold increase in astaxanthin production via stepwise reconstruction of the biosynthetic pathway and rational rewiring of the endogenous metabolism. The engineered strain produced up to 29.6 mg/g of astaxanthin (dry cell weight), which is the highest yield reported in the engineered chassis to date. Moreover, multi-omics analyses revealed that establishing a high astaxanthin flux may enhance photosynthesis and central metabolism in the engineered strain to compensate for the depleted pigments, which could be valuable for astaxanthin overproduction. This study presents a novel alternative for high-efficiency biosynthesis of astaxanthin directly from CO2.

19.
Biotechnol Adv ; 43: 107578, 2020 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-32553809

RESUMO

Photosynthetic cyanobacteria are capable of utilizing sunlight and CO2 as sole energy and carbon sources, respectively. With genetically modified cyanobacteria being used as a promising chassis to produce various biofuels and chemicals in recent years, future large-scale cultivation of cyanobacteria would have to be performed in seawater, since freshwater supplies of the earth are very limiting. However, high concentration of salt is known to inhibit the growth of cyanobacteria. This review aims at comparing the mechanisms that different cyanobacteria respond to salt stress, and then summarizing various strategies of developing salt-tolerant cyanobacteria for seawater cultivation, including the utilization of halotolerant cyanobacteria and the engineering of salt-tolerant freshwater cyanobacteria. In addition, the challenges and potential strategies related to further improving salt tolerance in cyanobacteria are also discussed.


Assuntos
Cianobactérias , Tolerância ao Sal , Biocombustíveis , Cianobactérias/genética , Engenharia Genética , Engenharia Metabólica , Fotossíntese , Água do Mar
20.
Artigo em Inglês | MEDLINE | ID: mdl-32528943

RESUMO

The fast-growing cyanobacterium Synechococcus elongatus UTEX 2973 (Syn2973) is a promising candidate for photosynthetic microbial factory. Seawater utilization is necessary for large-scale cultivation of Syn2973 in the future. However, Syn2973 is sensitive to salt stress, making it necessary to improve its salt tolerance. In this study, 21 exogenous putative transporters were individually overexpressed in Syn2973 to evaluate their effects on salt tolerance. The results showed the overexpression of three Mrp antiporters significantly improved the salt tolerance of Syn2973. Notably, overexpressing the Mrp antiporter from Synechococcus sp. PCC 7002 improved cell growth by 57.7% under 0.4 M NaCl condition. In addition, the metabolomics and biomass composition analyses revealed the possible mechanisms against salt stress in both Syn2973 and the genetically engineered strain. The study provides important engineering strategies to improve salt tolerance of Syn2973 and is valuable for understanding mechanisms of salt tolerance in cyanobacteria.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...