大肠杆菌Nissle 1917株鞭毛展示6His标签的构建及相关生物学特性分析

为探索大肠杆菌Nissle 1917株(EcN)鞭毛展示的应用,本研究以重组质粒p UC18-fli C为模板,反向PCR产物经DpnⅠ、Exnase^(TM)Ⅱ重组环化,将6His标签基因分别插入无质粒大肠杆菌Nissle 1917(EcNcured of its two cryptic plasmids p MUT1和p MUT2;EcNc)fli C高变区774 bp^775 bp和792 bp^811 bp之间,构建嵌合鞭毛基因片段fliC01和fliC02。分别将其克隆于自杀性载体pRE112中,构建重组质粒pRE112-fliC01和pRE112-fliC02,并分别转化至EcNc中。通过一次重组和二次重组将嵌合鞭毛基因整合于EcNc基因组中,构建无抗性筛选的重组菌株EcNc fliC01和EcNc fliC02。对重组菌株进行生长状况、鞭毛形成以及体外细胞黏附试验和小鼠体内定植试验检测,结果表明EcNc fliC01和EcNc fliC02的生长未受影响,表达的嵌合鞭毛能够被H1多抗或His-Tag单克隆抗体识别并组装形成鞭毛丝;重组菌对IPEC-J2细胞的黏附能力及小鼠肠道定植能力与亲本株EcNc相比无显著性差异。本实验结果为进一步研究EcNc鞭毛展示技术应用于活疫苗研制奠定了基础。

Effect of a specific Escherichia coli Nissle 1917 strain on minimal/mild hepatic encephalopathy treatment

BACKGROUND Hepatic encephalopathy(HE)can be considered a result of dysregulated gutliver-brain axis function,where cognitive impairment can be reversed or prevented by the beneficial effects induced by"gut-centric"therapies,such as the administration of nonabsorbable disaccharides,nonabsorbable antibiotics,probiotics and prebiotics.AIM To assess the short-term efficacy and safety of the probiotic Escherichia coli Nissle(EcN)1917 strain compared to lactulose and rifaximin in patients with minimal/mild HE.METHODS From January 2017 to March 2020,a total of 45 patients with HE were enrolled in this prospective,single-centre,open-label,randomized study.Participants were randomly assigned at a ratio of 1:1:1 to one of the treatment groups:The EcN group(n=15),lactulose group(n=15)or rifaximin group(n=15)for a 1 mo intervention period.The main primary outcomes of the study were changes in serum ammonia and Stroop test score.The secondary outcomes were markers of a chronic systemic inflammatory response(ІL-6,ІL-8,and IFN-γ)and bacteriology of the stool flora evaluated by specialized nonculture techniques after a 1 mo intervention period.RESULTS Patients who were given rifaximin or EcN showed a more significant reduction in serum ammonia and normalization of Bifidobacteria and Lactobacilli abundance compared to the lactulose group.However,the most pronounced restoration of the symbiotic microflora was associated with EcN administration and characterized by the absence of E.coli with altered properties and pathogenic enterobacteria in patient faeces.In the primary outcome analysis,improvements in the Stroop test parameters in all intervention groups were observed.Moreover,EcN-treated patients performed 15%faster on the Stroop test than the lactulose group patients(P=0.017).Both EcN and rifaximin produced similar significant reductions in the proinflammatory cytokines INF-γ,IL-6 and IL-8.EcN was more efficient than lactulose in reducing proinflammatory cytokine levels.CONCLUSION The use of the probiotic EcN strain was safe and quite efficient for HE treatment.The probiotic reduced the ammonia content and the level of serum proinflammatory cytokines,normalized the gut microbiota composition and improved the cognitive function of patients with HE.The application of the EcN strain was more effective than lactulose treatment.

E.coli Nissle 1917(EcN)curli菌毛和鞭毛对其生物被膜形成的影响

E.coli Nissle 1917是被广泛认可的益生菌,可以通过形成生物被膜定殖在肠道中抑制沙门氏菌等病原菌的生长。通过λ-Red同源重组系统构建curli菌毛合成基因(csgA)和鞭毛调控基因(hnsA)突变菌株,探究curli菌毛和鞭毛对EcN生物被膜形成的影响。结果表明,curli菌毛对EcN运动能力以及生物膜形成没有影响;EcNΔhnsA菌株的运动能力下降,生物被膜含量升高,说明鞭毛通过促进EcN运动,抑制细菌的附着,从而抑制生物膜的形成。

Minimizing endogenous cryptic plasmids to construct antibiotic-free expression systems for Escherichia coli Nissle 1917

The probiotic bacterium Escherichia coli Nissle 1917(EcN)holds significant promise for use in clinical and biological industries.However,the reliance on antibiotics to maintain plasmid-borne genes has overshadowed its benefits.In this study,we addressed this issue by engineering the endogenous cryptic plasmids pMUT1 and pMUT2.The non-essential elements were removed to create more stable derivatives pMUT1NR△and pMUT2HBC△.Synthetic promoters by integrating binding motifs on sigma factors were further constructed and applied for expression of Bacteroides thetaiotaomicron heparinaseⅢand the biosynthesis of ectoine.Compared to traditional antibiotic-dependent expression systems,our newly constructed antibiotic-free expression systems offer considerable advantages for clinical and synthetic biology applications.

益生菌大肠埃希菌EcN研究进展

1917年，德国医生AlfredNissle从一名士兵的粪便中第一次分离出无致病性的大肠埃希菌E．colinissle1917（EcN），这位士兵在一次严重的志贺菌爆发中未患肠炎。其后，各种研究证实了EcN的益生菌特性并促进其在临床中的应用。