Significance Bacteria have evolved intricate regulatory networks to coordinate their metabolism with internal and external signals of their status. The regulatory phosphotransferase systems (PTSs) constitute a key part of these intricate circuits, with their signal transduction cascades participating in multiple regulatory functions. Although two major systems have been described as being involved in regulating carbon and nitrogen pools, there is very little information on their physiological role in vivo under real-time conditions. In this work we demonstrate the role of PTS as an integrated system, widely conserved in proteobacteria, acting as a complex biological sensor-actuator device enabling bacterial cells to posttranslationally alter bacterial physiology and balance carbon and nitrogen availability.