Motility And Physiological Process Study Of Different Bacteria By Microscopic Tracking Techniques

Bacterial microscopic tracking technique,which is a newly-developed technique partly adopted from colloidal science,has become an important tool for microbiological studies,particularly in the research area where it requires the dynamic information of cell behavior at the single cell level.By this tracking technique,a time series data of microscopic images of cells are first processed and analyzed,then the trajectory of cell behavior can be constructed by linking cell data at differen time points using tracking algorithm,which form the basis for further statistical analysis of specific cell activities.It can also work together with fluorescence labelling techniques,which expand its appliations greatly in micriobiology studies.This technique enables us to obtain detailedand quantitative information about cell behavior such as motility and biofilm formation etc.with a single-cell resolution,and help us get a better understanding on the mechanism of these cell behaviors at the single-cell level.In this work,by applying the bacterial tracking technique,the single-cell motility of Sporosarcina pasteurii was analysed and the dynamics of microbially induced calcium carbonate precipitation was studied in situ and in real-time.The growth of micron-scale precipitates and the occurrence and dissolution of many unstable sub-micrometer calcium carbonate particles were observed.The maximum growth rate of calcium carbonate under agar was one half of the rate in liquid.We found that micrometer-sized calcium carbonate precipitates did not grow on the substances with negative charge(such as bacterial cells,PS particles),but bacterial cells and EPS had an effect on the morphology and mineralogy of precipitates.Interestingly,the growth of new precipitation clearly occurred on the precipitates collected from older runs.This study provides new insights into the dynamic regulation of microbially induced calcium carbonate precipitation.Then we studied the Myxococcus xanthus predation dynamics on Escherichia coli at the single-cell level.The residence time of Myxococcus xanthus was ?280 s,and plasmolysis of E.coli during predation was observed.By quantitatively characterization of their solitary predatory behavior,Myxococcus xanthus cells were found to respond with slower motion and about 4.5 times faster of lysing when contacting live prey than when contacting dead prey.Leading pole-contact mode is the major contact-dependent killing mode.72% of Myxococcus xanthus cells were found to move away directly just after lysing the prey cells and leave behind a large part of the dead cells unconsumed,indicating that solitary predation by Myxococcus xanthus is not efficient.Our results provide insight to understand Myxococcus xanthus collective predation from the perspective of their solitary predatory behavior,which may expand the application of predator-prey interactions in agricultural and medical fields.Finally,using the bacterial tracking technique together with fluorescence labelling techniques,we analysed the motility modes of Vibrio cholera and characterized quantitatively MSHA pili and their role in surface attachment.The results indicated that the number of MSHA pili increased linearly as cell grew.The attachment process was also revealed: when MSHA pili contacted with surface,the cells showed a short pause.Then the cell rotated around the attached pili as a fixed point driven by flagellum and finally attached.During the attachment process,some cells can detach and be free again.In 1% MC,the bacteria rotation period was ?0.7 s,and showed a negative linear correlation with swimming speed.The roles of MSHA pili in two types of motility behavior were also studied.Our results revealed a detailed picture of MSHA pili-surface interaction during the surface attachement process of Vibrio cholera.In conclusion,the bacterial microscopic tracking technique was successfully applied in our studies.We observed bacterial motilities with different modes at the single-cell level and studied the dynamics of several physiological processes.Our bacterial tracking system will provide a technical platform for future studies in the area of microbial studies that require single-cell resolution such as microbial predation and biofilm formation etc.