Bacteria are able to inhabit and survive vastly diverse environments. This enormous adaptive capacity depend on their ability to perceive cues from the micro-environment and process this information accordingly to mount appropriate metabolic responses and ultimately sustain homeostasis. From systems perspective, microbial cells conceal significant degree of organismal complexity, which may only be managed by continuous bulk cellular information flow and processing, inside the cell, between other cells and the environment. In this respect, reversible covalent modification of proteins is one of the universal mode of information flow mechanism used to regulate metabolism in all organisms. More than 30 types of post translational modifications have been identified, where phosphorylation constitutes nearly half of them. Bacterial cells possess several modes of phosphoprotein mediated information flow mechanisms. Histidine kinases and two component systems, bacterial tyrosine kinases, Hanks type serine/threonine kinases, atypical serine kinases and arginine kinases have been identified in many species.