Much knowledge has been gained for the last 30 years about the effects of pressure on bacteria, and various pressure-based technologies have been designed. The development of modern molecular biology techniques (e.g., DNA microarrays) as well as the technological advances realized in the manufacturing of robust sampling and high-pressure devices has allowed these advances. Not only the direct effects on cell components (membranes, proteins, and nucleic acids) have been unraveled, but also the cellular response to pressure has been investigated by means of transcriptome and proteome analyses. Initially, research was performed by marine biologists who studied the microorganisms living in the deep sea at pressures of 1,000 bar. In parallel, food technologists developed pressure-based methods for inactivating microorganisms without altering the food properties as much as with temperature treatment. The preservation of specific product properties is also the rationale for pressure-based methods for the disinfection of biomaterials and for vaccine production. Therefore, attention was first focused on the "killing" potential of high pressure. On the other hand, there has been a growing interest in using elevated pressures (up to similar to 10 bar) for enhancing the productivity of bioprocesses. In this case, no killing effect was sought, but pressure was applied to "boost" the process by enhancing the oxygen transfer to the cell culture. This paper gives an overview on the effects of pressures in the range of 1 bar to 10 kbar on bacteria and presents the major and most recent achievements realized in the development of pressure-based biotechnological applications.