| Microbial fuel cells(MFCs)are promising for generating bioenergy and treating organic waste simultaneously.However,low electricity power output is one of the major bottle necks in the practical application of MFCs.Therefore,molecular engineering plays a pivotal role in improving electricity power output of electricigens and promoting the development of bioenergy.Pseudomonas aeruginosa is an important microorganism of electricigens and received extensive attention,because it can secrete phenazines compounds,a class of electron transfer mediators.Pseudomonas aeruginosa PAOI is an model organism,so its genome sequencing has completed and its molecular operating system is matured.IrrE is an important global regulator and has crucial function on many pathways of D.Radiodurans.Meanwhile,the power output of Pseudomnoas aeruginosa is affected by a variety regulatory networks.So,whether there would be an effect on the power output of Pseudomnoas aeruginosa with the expression of IrrE.In this study,we explored the influence on power output with IrrE gene heterogeneous expression in Pseudomnoas aeruginosa,and the mechanism of this process was also researched.Our results will provide a new strategy and application example for the construction of electricigens with high electrochemical activity.In this study,we investigated that IrrE could expressed in P.aeruginosa by His-tag purification and Western Blot analysis,and analyzed the effect on growth characteristics of P.aeruginosa and spectrum of substrate utilization by drawing the growth curve and BioLog.The results showed that the expression of IrrE could extend the logarithmic phase of P.aeruginosa,increase biomass,and effect the metabolism of a variety of substrates.This work provide that IrrE can play roles in P.aeruginosa.And then,we inoculated the IrrE-recombinant bacteria to MFCs to explore the influence of IrrE expression on bioelectricity of P.aeruginosa.The results showed that the time needed to reach the steady status was shortened to 250 h,which shortened 24.24%compared to the control strain,the maximum power density of P.aeruginosa-irrE-inoculated MFC was enhanced to 56.00 mW/m2,which increased 71.30%compared to the control strain,and the voltage of P.aeruginosa was increased to 203 mV,which increased 34.40%compared to the control strain.All of the results indicated that the expression of IrrE could improve the bioelectricity of P.aeruginosa.Further,the results also showed that the internal resistance of MFCs reduced to 554 ?,about 18.95%,and the concentrate of pyocyanine increased to 0.16 mg/L,which increased 33.6%compared to the control strain.The results of real-time quantitative PCR showed that the transcription of glK(a key gene in glycolytic pathway),phzM and rhll(genes with positive regulation in the synthesis pyocyanine)were increased,and the transcription of rpoS and pmpR(genes with negetive regulation in the synthesis pyocyanine)were decreased.Besides,there were evident changes in the transcription of some genes about biofilm formation,such as bdlA,some genes about pili and cilium assembly,such as pelF,pilT,filC and filA,some genes about stress resistant,such as katA,katB,sodM,groEL and recA.In conclude,the expression of IrrE could increase power output by reducing internal resistance and increasing the content of the electros mediators,and it could change the transcription level of many key genes in central metabolic pathway,in pili,flagellum and biofilm formation pathway,and in stress tolerance. |
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