Interaction Force Of Different Growth Phase P.Putida With Goethite

Soil is the fundation of human survival and development.The adhesion of bacteria onto mineral surfaces is ubiquitous in soil and associated environments,it can affect a series of fundamental biogeochemical processes including soil aggregates formation,mineral dissolution,pollutants degradation and pathogen fate.However,the process and mechanism of bacteria-mineral interactions is still not fully explained.In this study,Pseudomonas putida and goethite were selected to explore the adhesion patterns.Conventional chemical and modern instrumental techniques such as atomic force microscopy,cell probe,synchrotron,isothermal titration calorimetry,Fourier transform infrared spectroscopy,potentiometric titration and contact angle were employed to study the adhesion behavior of bacteria with mineral under the influence of growth phase.The main findings are listed as follows:(1)Information of the contact force of different growth phase bacteria with goethite was directly obtained.The force order is stationary phase>decline phase>exponential phase.For the instant contact,the force value were 879 pN,548 pN and 199 pN,respectively.The force value of EPS(Extracellular Polymeric Substances)-removal,protein-removal and polysaccharides-removal bacteria with goethite were 141 pN,647 pN and 684 pN,respectively.Time-dependent effect was observed.That is,the interaction force increases as the contact time increases.In this study,the maximum adhesion force was ~4 N for stationary phase bacteria when contact time is 10 s.(2)Surface properties of different growth phase baceteria were characterized.The zeta potential,amount of surface functional groups and hydrophobicity of different growth stages bacteria were consistent with the force behavior.Which means that the zeta potential,amount of surface functional groups and hydrophobicity can be used to explain the interaction pattern of bacteria with mineral.The FTIR and synchrotron results showed that the changes of surface protein and polysaccharides are the main reason of the adhesion behavior.(3)The contribution of surface biomacromolecule towards adhesion was determined,the important contribution of EPS in adhesion behavior was proved,and the pattern of bacteria adhesion onto mineral was concluded.At the moment of contact,the contribution of three different biomacromolecules to adhesion was EPS>polysaccharide=protein;as the contact time increased,polysaccharides lead the adhesion,and the contribution was ranked as EPS>polysaccharide>protein.