In agro-food industry, the hygiene of solid surfaces is of primary importance to guarantee products safe to consumption. One of the keys for this safety improvement is to understand and identify the mechanisms of microbial cell adhesion to solid surfaces or filtration membranes. The yeast cell Saccharomyces cerevisiae (about 5 µm in diameter) was selected because it constitutes a relevant tool to study the fungal biofilms. The adhesion of this micro-organism to a model solid surface, which corresponds to the first critical step of biofilm formation, has been investigated. An optical tweezer device developed at the Laboratoire de Rhéologie was implemented on yeast cells in contact with well-characterized glass supports. A particular attention was devoted to the non-invasive nature and thermal effect of the micromanipulation technique. Two observation planes were carried out firstly to obtain quantitative measurements of adhesion forces and secondly to characterize in-situ, at the micrometer length scale, the corresponding mechanisms involved. The effect of cultivation of S.cerevisiae yeast cells on their subsequent adhesion/detachment from the glass surface was particularly investigated. The results highlighted various mechanisms of the adhesion process, depending on the ionic strength, the contact time and the type of yeast (rehydrated/cultured cells). The rehydrated yeast strongly adhered at a weak ionic strength although the cultured one did not. Nevertheless, the percentage of adhered cells strongly increased with the ionic strength for the two types of yeasts. Differences in mobility were brought to the fore at various ionic strengths. Our observations showed that yeast cells adhered to the glass surface in a local manner by discrete anchoring sites. These results clearly demonstrate that the micro-rheological approach is essential to analyze the adhesion mechanisms at the relevant local scales of biological systems.