The Electricity-producing Microorganism Geobacter Sulfurreducens PCA_metabolic Network Optimization

Social development have promoted human to constantly go over the relationship between self-progress and natural environment.Exploring the Microbial Fuel Cells(MFCs)gives full expression to sustainable development thing.MFCs are a class of ideal technologies that function via anaerobic respiration of electricigens,which couple current generation with environmental restoration.Though MFCs are certainly of potential applications,widespread utilization of MFCs cannot be expected because of the current bottleneck in power production and high cost of materials.An in-depth understanding of microbial respiration mechanism and cellular flux distribution is of great importance in engineering microbes to increase their respiration rates.We employed in silico algorithm FBA(Flux Balance Analysis)to simulate various growth and respiration conditions of Geobacter sulfurreducens PCA with a fixed acetate uptake rate.The results indicated the flux of reactions directing acetate towards dissimilation to generate electrons increases under the suboptimal growth condition,resulting in an increase in the respiration rate and a decrease in the growth rate.Microbes growing slowly have the ability to make good use of fuel in MFCs.Alternate respiratory states exist under one growth state as a result of the redundant pathways in the metabolic network.Of all patterns the one that maximizes the respiratory rate is of particular interest to be achieved for strain development by systematic metabolic engineering.We employed FVA(Flux Variant Analysis)to simulate alternate flux distributions under a same suboptimal growth condition.The results indicated under minimum respiration,less acetate towards TCA cycle(Tricarboxylic Acid Cycle)and the total secretion of formate cause electron loss and subsequent large respiratory rate difference from maximum respiration.A perfect current-generating metabolism variant of G..sulfurreducens was constructed by deletion of several transport enzymes.The perfect metabolism state consists of simultaneous suboptimal growth and maximum respiration.Under this perfect condition,the pore space of MFCs is wider without excess biomass accumulation and electricigens maximize utilization of limited fuel.Finally we employed a bilevel programming framework Optknock to identify gene knockout strategies for desired current-generating metabolism state,which consists of simultaneous suboptimal growth and maximum respiration.The computational procedure could identify not just straightforward but also nonintuitive knockout strategies,which allow us to manipulate potential target genes for strain improvement.Real experiments need to be performed to verify potential metabolic engineering targets.Combined these developed and developing perfect optimization algorithms with real experiments,it's very possible to achieve the desired current-generating metabolism of simultaneous suboptimal growth and optimal respiration,as well as subsequent widespread applications of the promising MFCs technology in the not too distant future.