Single-molecule biotechnology for protein researches

Cells employ proteins to perform metabolic functions and maintain active physiological state through charge transfer and energy conversion.These processes are carried out in a narrow space precisely and rapidly,which,no doubt,bring great difficulty for their detection and dissection.Fortunately,in recent years,the development and expansion of single-molecule technique in protein research make monitoring the dynamical changes of protein at single-molecule level a reality,which also provides a powerful tool for the further exploration of new phenomena and new mechanisms of life activities.This paper aims to summarize the working principle and essential achievements of single-molecule technique in protein research in recent five years.We focus on not only dissecting the difference of nanopores,atomic force microscope,scanning tunneling microscope,and optical tweezers technique,but also discussing the great significance of these single-molecule techniques in investigating intramolecular and intermolecular interactions,electron transport,and conformational changes.Finally,the opportunities and challenges of the single-molecule technique in protein research are discussed,which provide a new door for single-molecule protein research.

Putative functions of EpsK in teichuronic acid synthesis and phosphate starvation in Bacillus licheniformis

Extracellular polymeric substances(EPSs)are extracellular macromolecules in bacteria,which function in cell growth and show potential for mechanism study and biosynthesis application.However,the biosynthesis mechanism of EPS is still not clear.We herein chose Bacillus licheniformis CGMCC 2876 as a target strain to investigate the EPS biosynthesis.epsK,a member of eps cluster,the predicted polysaccharide synthesis cluster,was overexpressed and showed that the overexpression of epsK led to a 26.54%decrease in the production of EPS and resulted in slenderer cell shape.Transcriptome analysis combined with protein-protein interactions analysis and protein modeling revealed that epsK was likely responsible for the synthesis of teichuronic acid,a substitute cell wall component of teichoic acid when the strain was suffering phosphate limitation.Further cell cultivation showed that either phosphate limitation or the overexpression of teichuronic acid synthesis genes,tuaB and tuaE could similarly lead to EPS reduction.The enhanced production of teichuronic acid induced by epsK overexpression triggered the endogenous phosphate starvation,resulting in the decreased EPS synthesis and biomass,and the enhanced bacterial chemotaxis.This study presents an insight into the mechanism of EPS synthesis and offers the potential in controllable synthesis of target products.

三段式谷氨酸棒杆菌发酵生产生物絮凝剂的过程及动力学模拟(英文)

Fermentation of bioflocculant with Corynebacterium glutamicum was studied by way of kinetic modeling.Lorentzian modified Logistic model, time-corrected Luedeking–Piret and Luedeking–Piret type models were proposed and applied to describe the cell growth, bioflocculant synthesis and consumption of substrates, with the correlation of initial biomass concentration and initial glucose concentration, respectively. The results showed that these models could well characterize the batch culture process of C. glutamicum at various initial glucose concentrations from 10.0 to 17.5 g·L-1. The initial biomass concentration could shorten the lag time of cell growth,while the maximum biomass concentration was achieved only at the optimal initial glucose concentration of16.22 g·L-1. A novel three-stage fed-batch strategy for bioflocculant production was developed based on the model prediction, in which the lag phase, quick biomass growth and bioflocculant production stages were sequentially proceeded with the adjustment of glucose concentration and dissolved oxygen. Biomass of2.23 g·L-1was obtained and bioflocculant concentration was enhanced to 176.32 mg·L-1, 18.62% and403.63% higher than those in the batch process, respectively, indicating an efficient fed-batch culture strategy for bioflocculant production.