Cell wall biogenesis; teichuronic acid biosynthesis. By phosphate starvation, via the PhoP/PhoR two-component regulatory system. The nature of the anionic polymer present in the cell wall of B.subtilis depends on phosphate availability. Under phosphate-replete growth conditions teichoic acids are present, whereas under phosphate-depleted conditions, at least part of the wall teichoic acid is replaced with teichuronic acid, a non-phosphate containing anionic polymer. The synthesis of teichuronic acid is accompanied by degradation of teichoic acid and reutilization of liberated phosphate for other cellular processes such as nucleic acid synthesis.