The fast mobilisation of inorganic pollutants by the colloidal and mobile fraction of soils, and in particular biotic colloids (bacteria, algae, fungi, virus, etc.), is now identified as an important secondary transport process that can lead, under specifc conditions, to accelerated and potentially dominant pollutant transfer towards aquifers. The involved mechanisms remain howecver poorly understood. In order to better understand the role of bacterial cells in metal leaching, we conducted a coupled study under static and dynamic conditions. Firstly we evaluated Zn and Cd metal biosorption onto active or inactive Gram negative bacteria (Escherichia coli and Cupriavidus metallidurans CH34) by characterizing the sub-cellular distribution of the metals through a cell disruption approach. The quantification of Zn and Cd in extracellular, membrane and cytoplasm compartments of the cells permitted to show that metals are unequally distributed between the three cell compartments and also between the two different bacteria. Metals internalization appeared surprizingly to be the dominant accumulation process of metals (high cytoplasm contents). These results suggest that adsorption onto cell surface is only a first step in metal management by bacteria and that bacteria can internalize important amounts of heavy metals. The so-determined thermo-dynamic reactivity constants were used to fit metal breakthrough curves performed in natural sand columns. Transport experiments of bacterial cells, metals or mixtures of bacteria and/or metals demonstrated that bacteria are able to enhance and accelerate Cd and Zn transport in natural sand columns. This transport process was shown to dominate metal aqueous transport and was correctly fitted using a combined transport and geochemical modeling approach. Altogether, these results show that, under specific conditions, bacterial cells can increase metal pollutants mobility in soils, which can be damaging for environmental quality but also interesting in terms of soil remediation perspectives.