Simulation Analysis Of Microbial Aggregation Process At Microscale

In the face of environmental stress,microorganisms form groups in an aggregated way to withstand adverse environmental impacts.The formation and growth of microbial aggregates is the result of complex interactions between microorganisms and their environment,and is a reflection of the behavior of microorganisms actively or passively regulating and adapting to their environment.However,the current understanding of how environmental stress stresses microbial aggregation processes is not clear,and there is a lack of quantitative description of microbial aggregation processes at microscales.In this paper,the bacterial and unicellular algae was studied as the research object,and the microscopic spatiotemporal variation patterns of water chemistry and microbial behavior were explored under restrictive nutrient conditions and disinfectant stress,and a mathematical model of microbial aggregation process at microscales was constructed to analyze bacteria under environmental stress.The mechanism of the influence of environmental stimuli on its initial attachment and aggregation was discovered,thus providing theoretical support for controlling and utilizing microbial aggregation behavior.Firstly,Pseudomonas aeruginosa was used as the research object to investigate the effect of bacterial motility on its initial attachment under different nutrient conditions.The results showed that,with the increase of nutrient concentration,the bacterial velocity and attachment increased first and then decreased,which was the highest with the dilution ratio of 1/50.Mathematical simulation results show that,shaped by environmental stimulus and microscopic concentration gradients,moderately restrictive nutrient conditions promoted bacterial motility,which helps to increase the chances of bacterial foraging and the collision frequency between bacteria-bacteria and bacteria-surface,and thus promoting surface attachment and aggregation.Secondly,the unicellular algae were used as the research object to study the movement and aggregation behavior of Chlamydomonas microsphaera under different initial chlorine concentrations.The results showed that low-level chlorine increased the velocity and aggregation of Chlamydomonas microsphaera,while high-level chlorine inhibited its movement,thus not conducive to its aggregation.The main reason affecting the motility of Chlamydomonas microsphaera is the stimulating effect caused by the environmental stimulus of chlorine disinfection.The difference of the concentration distribution at microscales posed insignificant effect on the cell motility.However,the microscopic concentration gradient regulates the algae to move to a low concentration area of chlorine.The aggregation behavior of Chlamydomonas microsphaera was beneficial to improve its survival rate in the disinfectant environment.Finally,on the basis of the above studies,the effects of nutritional conditions on bacterial population structure were studied.The results showed that under nutrient limitation,the co-inoculation of the two bacteria facilitated the initial attachment,and the more uniform the inoculation group,the higher the attached rate;while under the nutrient-rich condition,the higher the proportion of non-motile bacteria,the more favorable the initial attachment.Nutritional conditions affect the bacterial interaction by regulating the velocity of movement,and then change the structure of the attached microbial flora.Increasing the nutrient concentration will reduce the proportion of motile bacteria in the biofilm.As time goes by,the proportion of non-motile bacteria increases.