► We analyzed the structure and activities of microbial communities in two different unvegetated glacier forefields throughout three seasons. ► Nutrient status at both sites changed during the three sampling seasons. ► Microbial community structures appeared affected by change in climate. ► Viable microbial communities did not change significantly. This study addresses the relationship between the dynamical changes of soil properties and of the viable bacterial communities in the unvegetated forefields of two receding glaciers, Damma and Tsanfleuron (Switzerland). In spring, summer and autumn, the soils were characterized in terms of their pH, TC, TN and soluble nutrients. Bacterial community structures were assessed through terminal restriction fragment length polymorphism (T-RFLP) profiling of the bacterial 16S rRNA at both the DNA and RNA level (RT-T-RFLP), and through the creation of cDNA-based clone libraries. In addition, the general activities of the communities were analyzed through enzymatic assays. In general, while TC and TN varied only slightly between the seasons, the extractable nutrients had significantly lower concentrations in summer. Canonical correspondence analysis (CCA) showed clear correlations between bacterial community structures at each sampling season and environmental parameters. Climatic factors such as temperature, precipitation and sun hours appeared to be the most strongly correlated with the T-RFLP profiles. Investigation of RT-T-RFLP and cDNA-based clone libraries did not show marked changes of the viable members of the bacterial community. The class of α-Proteobacteria was the dominant bacterial component throughout the year in the profiles, suggesting that they are not strongly affected by seasonal change. However, other important groups such as Actinobacteria and Firmicutes showed changes in relative abundance and composition. Our results suggest that unvegetated glacier forefields experience temporal physico-chemical variations which may not affect the dominant viable components of the bacterial communities.