Research On Slime Forming Bacteria Chemotactic Movement Under The Action Of Alternating Magnetic Field

Microbial fouling is an important component of fouling in circulating cooling water system.It grows fast and contributes to the comprehensive accumulation of other kinds of fouling,resulting in increasing of fouling resistance on heat transfer surface,acceleration corrosion of equipment corrosion,at last potential safety hazards and economic losses.Movement is the key to the survival and reproduction of microorganisms in circulating cooling water.Studying its process can help to understand the formation principle and growth mechanism of microbial fouling more clearly,which is of great significance for taking effective measures on fouling prophylaxis and treatment.The anti-fouling method of the electromagnetic field is a new technology,which is safe and environmentally friendly.At present,the research on electromagnetic field acting on microorganisms is mostly based on its influence on the growth and inactivation of microorganism,but little on the effect on the movement.Based on the above problems,the effect of alternating magnetic field perpendicular to the direction of nutrient source on the chemotactic movement of slime-forming bacteria,a typical scaling microorganism in cooling water was studied.Firstly,based on the movement mechanism and the force analysis of bacteria in alternating magnetic field,a movement model was put forward,and a simulation interface for the chemotactic movement was designed.The trajectories of a single bacteria and bacterial colony under alternating magnetic fields with different frequencies(50Hz,100Hz)and different magnetic induction intensity(10mT,20mT)were simulated.The motion state of slime-forming bacteria towards nutrient source under magnetic field could be reflected by the simulation of bacteria colony movement in two-dimensional plane,which directly showed the influence of magnetic field on the chemotactic movement.The average displacement and velocity in the direction of nutrient source were calculated.The results show that the alternating magnetic field perpendicular to the direction of nutrient source promotes the chemotactic movement.The lower the frequency and the greater the magnetic induction intensity,the stronger the promotion effect and the faster the chemotaxis speed will be.Secondly,in order to validate the simulation results,a magnetic field generator was designed to generate an alternating magnetic field perpendicular to the direction of nutrient sources for capillary assay experiment.Plate colony-counting method was used to calculate the accumulation amount of bacteria in capillaries at different experimental time,in order to measure the strength of the chemotactic movement of slime-forming bacteria.The accumulation amount under different frequencies and magnetic induction intensities were compared.The results have shown that the accumulation amount under magnetic field is larger than that without magnetic field.The lower the frequency and the greater the magnetic induction intensity,the larger the accumulation amount will be.Finally,according to the bacteria colony migration parameter model,the data of capillary assay experimental was substituted to quantify the random motion coefficient,the chemotactic motion coefficient,the motion coefficient in magnetic field and the colony velocity in the direction of nutrient source.The average velocity of slime-forming bacteria obtained by simulation was compared with the colony velocity.The change trend is the same,and the relative error is between 2.11% and 33.15%,which verified the correctness of the simulation.In summary,a movement model of slime-forming bacteria under the action of alternating magnetic field was put forward and the trajectory was simulated.The influence of alternating magnetic field on the chemotactic movement characteristics was analyzed and the correctness of the model and simulation was verified by the experimental results.The model and simulation of the chemotactic movement of slime-forming bacteria in this thesis are also applicable to other scaling microorganisms,which provides a theoretical basis for the study of the initial stage of microbial fouling formation,and has certain significance for exploring the mechanism of the anti-fouling method of the electromagnetic field.