The interaction of foreign implants with its surrounding environment is significantly influenced by the adsorption of proteins on the biomaterial surfaces, playing role in the microbial adhesion. Therefore, understanding protein adsorption on solid surfaces and its effect on microbial adhesion is essential to assess the associated risk of infection. The aim of this study is to evaluate the effect of conditioning by fibronectin (Fn) or bovine serum albumin (BSA) protein layers of silica (SiO2) surfaces on the adhesion and detachment of two pathogenic microorganisms: Pseudomonas aeruginosa and Candida albicans. Experiments are conducted under both static and hydrodynamic conditions using a shear stress flow chamber. Through the attended very low wall shear stresses the study reveals the link between the static and dynamic conditions of microbial adhesion. The results reveal that the microbial adhesion critically depends on: i) the presence of a protein layer conditioning the SiO2 surface, ii) the type of proteins and iii) the protein conformation and organization in the conditioning layer. In addition, a very distinct adhesion behaviour of P. aeruginosa is observed towards the two tested protein, Fn and BSA. This effect is reinforced by the amount of proteins adsorbed on the surface and their organization in the layer. The results are discussed in the light of Atomic Force Microscopy analysis of the organization and conformation of proteins in the layers after adsorption on the SiO2 surface, as well as the specificity in bacteria behaviour when interacting with these protein layers. The study also demonstrates the very distinctive behaviours of the prokaryote P. aeruginosa species compared to the eukaryote C. albicans ones. This underscores the importance of considering species-specific interactions between protein conditioning layer and different pathogenic microorganisms, which appear crucial in designing tailored anti-adhesive surfaces.