Study On The Secretion Of Shewanella Oneidensis MR-1 Extracellular Electron Mediator And The Degradation Characteristics Of TCP

The dissimilated metal reducing bacteria refer to a type of microorganism capable of reducing extracellular insoluble metal oxides by electrons obtained from oxidative phosphorylation of an organic substrate while releasing energy for growth of the microorganisms themselves.With the continuous research on such microorganisms,its metabolic function and the characteristics of adapting to extreme environment,making it play an increasingly important role in the process of environmental pollution control.The extracellular electron mediator is a redox active compound that contributes to the extracellular electron transport of microbes.It not only mediates extracellular electron transport,but also plays a special role in many microbial applications.Shewanella oneidensis MR-1 is a widely studied model of dissimilatory metal reduction,which can use metal ions and various organic pollutants as electron acceptors,and most Shewanella species can secrete flavin as extracellular electrons Mediator,but the specific mechanism is still unclear.Therefore,in order to further study the effects of environmental factors on the secretion of extracellular electron mediators of Shewanella and to expand the application of Shewanella in the field of environmental remediation.In this thesis,the model strain Shewanella oneidensis MR-1 was used as the experimental research object,based on the physiological characteristics of Shewanella oneidensis MR-1,by high performance liquid chromatography-mass spectrometry(LC-MS)And fluorescence spectroscopy(EEM)to screen and characterize the extracellular electron mediator riboflavin,investigate the effect of single environmental factors on the secretion of riboflavin,the response mechanism of environmental factors and riboflavin production was discussed in depth,and investigate the degradation characteristics of the refractory2,4,6-TCP by Shewanella oneidensis MR-1,which further expanded the electron acceptor range of Shewanella oneidensis MR-1 and provided more theoretical support for the application of extracellular electron transfer of Shewanella in environmental pollution control.The main research contents and results are as follows:(1)S.oneidensis MR-1 activation and qualitative testing of extracellular electronic mediators.According to Gram staining and scanning electron microscopy,it was confirmed that S.oneidensis MR-1 was successfully activated.The growth curves of MR-1 at 30? and 25?were investigated,the results showed that the stagn-ation period of MR-1 bacteria was shorter and the stability period could be reached faster when the culture temperature was 30?.LC-MS and EEM were detected by riboflavin standard and strain secretion,respectively.The results showed that the peak of the same period of time as the riboflavin standard appeared in the SIM picture of the secretion,and a typical core was observed in the exudate mass spectrum.The nucleoli ratio of the flavin standard was(m/z)377.1 and 242.2.In the three-dimensional fluorescence diagram of the secretion,it was found that a fluorescent substance corresponding to the standard was generated at an excitation wavelength of 450 nm,an emission wavelength of 530 nm,and an excitation wavelength of 370 nm and an emission wavelength of 450 nm.Thus,it was confirmed that S.oneidensi MR-1 produced riboflavin.(2)The effect of a single environmental factor on riboflavin secretion.The results showed that the secretion of riboflavin is closely related to the growth of bacteria,and riboflavin is still produced during the stagnation period.Sodium lactate,OD=1.5,1ml or 2ml of bacterial dosage,all can promote the secretion of riboflavin,while sodium acetate,glucose,bacterial dosage 5ml,supplemented N source for the secretion of riboflavin to inhibition.(3)Test for the degradation characteristics of S.oneidensis MR-1 against TCP.The test results show that S.oneidensis MR-1 is highly resistant to TCP and can grow in relatively high TCP concentrations.When the initial concentration of TCP is 20?M,the dosage of the cells is 2ml,and riboflavin is added,it is beneficial for the MR-1bacteria to degrade TCP.