Proteomic technologies are powerful tools to study the physiological response of bacteria to various environmental stress conditions. Complex protein toolkits coordinated by regulatory networks have evolved to accommodate bacterial survival under several stressing conditions, such as varying temperature or pH, and changes in nutrient availability. This manuscript provides an overview of the major achievements obtained by 2D gel based and non-gel based proteomic approaches for the study of adaptive response in bacteria. As an example, a study carried out on Streptococcus thermophilus response to various stresses is here reported. In this investigation, we used combined proteomic strategies to define proteomic maps useful to highlight protein profile variations following environmental challenges.