The phosphorelay system consists of four basic reactions. The first event is a signal from the environment which causes KinA, a sensor kinase (or other kinases) to autophosphorylate. The phosphate group is transferred to Spo0F, which is the response regulator. The transfer of phosphate from Spo0F~P to Spo0A is mediated via a phosphorylated enzyme intermediate Spo0B. The phosphorylated Spo0A goes on to activate the genes necessary for sporulation. The networks of signals which regulate the phosphotransfer network receives input from many sources so that the proper choice is made using an integrated view of the environmental and metabolic conditions of the bacterium. The signals covered in this paper include availability of glucose and fixed nitrogen, DNA damage, oxygen levels, redox potential, and stationary phase. variability.