As the habitats of bacteria, soil pore network and surface properties control the distribution, adhesion, and motility of bacteria in soils. These physical processes in turn influence bacterial accesses to nutrients and bacterial interactions. Our understanding on the pore- and surface-mediated bacterial interactions is currently limited. In this research, we evaluated the effects of soil pore confinement and surface adhesion on conjugation-based bacterial interactions. The interaction was measured by plasmid transfer between donor and recipient cells within the population of soil bacterium Pseudomonas putida. We found that the presence of porous sand media led to a net increase in conjugation frequency compared to sand-free liquid control. The increase is attributed to the facilitated effect of pore confinement on the collision of bacteria within pores. In contrast, bacterial adhesion to sand surfaces under elevated ionic strength conditions decreased the conjugation frequency as a result of mobility reduction on the surface. Such collision and adhesion mechanisms jointly drive the conjugation as a function of pore and surface properties of porous media. These results provide valuable insights into the roles of soil pores and surfaces in regulating horizontal gene transfer, an essential cell-to-cell interaction sustaining key processes of soil ecology and health.

作为细菌的栖息地，土壤孔隙网络和表面性质控制着细菌在土壤中的分布、粘附和运动。这些物理过程反过来影响细菌获取营养物质和细菌相互作用。目前我们对孔隙和表面介导的细菌相互作用的了解还有限。在这项研究中，我们评估了土壤孔隙限制和表面粘附对基于共轭的细菌相互作用的影响。通过土壤细菌恶臭假单胞菌群体中供体细胞和受体细胞之间的质粒转移来测量相互作用。我们发现，与无砂液体对照相比，多孔砂介质的存在导致共轭频率净增加。这种增加归因于孔隙限制对孔隙内细菌碰撞的促进作用。相反，在离子强度升高的条件下，细菌粘附到沙子表面会由于表面迁移率降低而降低结合频率。这种碰撞和粘附机制共同驱动作为多孔介质的孔隙和表面特性的函数的共轭。这些结果为了解土壤孔隙和表面在调节水平基因转移中的作用提供了宝贵的见解，水平基因转移是维持土壤生态和健康关键过程的重要细胞间相互作用。