Flagella and their property affect the transport and deposition behaviors of Escherichia coli in quartz sand

The effects of bacterial flagella as well as their property on the transport and deposition of bacteria were examined by using four types of Escherichia coli (E.coli) with or without flagella, as well as with normal or sticky flagella. Packed column, quartz crystal microbalance with dissipation (QCM-D), visible parallel plate flow chamber system, as well as visible flow chamber system packed with porous media system were utilized to investigate the deposition behaviors and the deposition mechanisms of bacteria with different property of flagella. We found that the presence of flagella favored E.coli deposition onto quartz sand/silica surfaces. Moreover, by changing the porous media porosity and directly observing the deposition process of bacteria in porous media, grain-to-grain contacts were found to be major sites for bacterial deposition. Particularly, flagella could help bacteria swim near and then deposit at grain-to-grain contacts. In addition, we found that due to the stronger adhesive forces, sticky flagella could further enhance bacterial deposition onto quartz sand/silica surfaces. Elution experiments showed that the portion of bacteria with flagella depositing onto secondary energy minima was relatively lower than bacteria without flagella, indicating that flagella could help bacteria attach onto sand surfaces more irreversibly. Clearly, flagella and their property would have obvious influence on the transport and deposition behaviors of bacteria in porous media. By removing the flagella or changing their property, the transport and deposition of bacteria in porous media can be altered. Particularly, bacterial flagella can be removed to facilitate the transport of bacteria in remediation system requiring high mobility of bacteria, while in system requiring the immobilization bacteria in porous media, bacteria with sticky flagella can be employed.