Influence Of Environmental Factors On Shewanella Oneidensis MR-1 Attachment In Bioelectrochemical Systems

In the bioelectrochemical system,the attachment behavior of bacteria on the electrode surface is crucial to the successful operation of the system.However,this attachment process is affected by many environmental factors,and the current research is not complete enough to understand the mechanism of biofilm formation on the electrode surface.hewanella oneidensis was selected as the model strain,using experimental research and statistical analysis methods,by simulating the two main external factors that affect the bacterial attachment behavior in the bioelectrochemical system,nutrients and Voltage,try to explore the influence of environmental factors in the bioelectrochemical system on its biofilm formation,and provide theoretical basis and data support for the effective use of the bioelectrochemical system.The main research results obtained are as follows:(1)The effect of different carbon source levels on the bacterial attachment process shows that the bacterial attachment amount under the limiting nutrient concentration(1 mmol/L sodium lactate solution)is the highest at the initial attachment stage(1/3 h-1 h),reaching 3.23±0.10×10~7cells/cm~2,the amount of attachment decreases with increasing nutrient concentration.Limiting nutrient concentration will increase the speed of bacteria and the production of extracellular polymers.At this time,the three factors that promote the attachment of bacteria from strong to weak are the carbon felt nutrient adsorption rate,extracellular polymer secretion and bacterial movement speed.At the stage of biofilm formation(8 h),the amount of bacteria attached was the highest at a sufficient nutrient concentration(40mmol/L sodium lactate solution),reaching5.04±0.26×10~7cells/cm~2.And then promote the bacterial attachment,the secretion of extracellular polymer and the speed of bacterial movement still promote the bacterial attachment behavior.(2)The influence of the gradient voltage condition on the bacterial attachment process shows that in the initial attachment stage,the attachment amount of bacteria on the electrode under 0.6 V applied voltage is the largest,reaching 6.87±0.18×10~7cells/cm~2.It can be seen that proper voltage application can increase the speed of bacteria and the formation of extracellular polymers.The secretion of extracellular polymer and the speed of bacterial movement in the initial attachment stage are two factors that promote the bacterial attachment behavior.In the biofilm formation stage,the amount of bacteria attached at 0.4 V was the highest,reaching 14.14±0.48×10~7cells/cm~2.At this stage,the speed of bacterial movement no longer promoted the amount of bacteria attached,but the secretion of extracellular polymers was different get bigger.At the same time,we found that both in the initial attachment stage and the biofilm formation stage,the amount of bacteria attached at 0.8 V was lower than that under no power.This result shows that proper voltage conditions are conducive to the attachment and growth of bacteria,while excessive voltage has an inhibitory effect on the attachment behavior of bacteria.(3)The effect of gradient voltage on bacterial attachment process under restrictive nutrient conditions shows that in the initial attachment stage,in restrictive nutrient conditions,the bacterial attachment amount under 0.6 V voltage is the largest,reaching 8.13±0.33×10~7cells/cm~2,which The peak of bacterial attachment under sufficient nutrient conditions at this stage.The two factors that promote the bacterial attachment behavior at this stage from strong to weak are the secretion of extracellular polymers and the speed of bacterial movement.In the biofilm formation stage,the bacterial attachment amount is still the most at 0.6 V,reaching 13.26±2.26×10~7cells/cm~2,which is slightly lower than the peak bacterial attachment amount under sufficient nutrition.This stage has a promoting effect on bacterial attachment behavior The two factors from strong to weak are the speed of bacterial movement and the secretion of extracellular polymers.This result shows that the double restriction condition is more conducive to the initial attachment of bacteria,but with time,the gradual lack of nutrients will have a certain inhibitory effect on the formation of bacterial biofilms.